Jawetz Microbio Flashcards by Patricia Ong

Which one of the following terms characterizes the interaction between a fungus and algae in a lichen?

(A) Parasitism (B) Symbiosis (C) Endosymbiosis (D) Endoparasitism (E) Consortia

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Which one of the following agents lacks nucleic acid?

(A) Bacteria (B) Viruses (C) Viroids (D) Prions (E) Protozoa

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Which one of the following is not a protist?

(A) Bacteria (B) Algae (C) Protozoa (D) Fungi (E) Slime molds

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Which one of the following agents simultaneously contains both DNA and RNA?

(A) Bacteria (B) Viruses (C) Viroids (D) Prions (E) Plasmids

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A 65-year-old man develops dementia, progressive over several months, along with ataxia and somnolence. An electroencephalographic pattern shows paroxysms with high voltages and slow waves, suggestive of Creutzfeldt-Jakob disease. This disease is caused by which of the following agents?

(A) Bacterium (B) Virus (C) Viroid (D) Prion (E) Plasmid

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Which of the following cannot be infected by viruses?

(A) Bacteria (B) Protozoa (C) Human cells (D) Viruses (E) None of the above

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Viruses, bacteria, and protists are uniquely characterized by their respective size. True or false?

(A) True (B) False

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Which of the following are prokaryotes?

(A) Archaebacteria (B) Protozoa (C) Viruses (D) Prions (E) Fungi

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Quorum sensing in prokaryotes involves

(A) Cell–cell communication (B) Production of pheromones (C) An example of multicellular behavior (D) Regulation of genes involved in diverse physiologic processes (E) All of the above

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Twenty minutes after ingesting a raw clam, a 35-year-old man experiences paresthesias of the mouth and extremities, headache, and ataxia. These symptoms are the result of a neurotoxin produced by algae called

(A) Amoeba
(B) Blue-green algae
(C) Dinoflagellates
(D) Kelp (E) None of the above

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Eubacteria that lack cell walls and do not synthesize the precursors of peptidoglycan are called

(A) Gram-negative bacteria
(B) Viruses
(C) Mycoplasmas
(D) Serovar variant
(E) Bacilli

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Archaebacteria can be distinguished from eubacteria by their lack of

(A) DNA (B) RNA (C) Ribosomes (D) Peptidoglycan (E) Nucleus

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A 16-year-old cystic fibrosis patient is admitted to the hospital. A sputum culture yields Burkholderia cepacia. Subsequently, there are two other patients with B. cepacia bacteremia, and the organism is cultured from the sputum of four additional patients. During this nosocomial outbreak of B. cepacia, 50 environmental and seven patient isolates are being subtyped to identify the source of the outbreak. Which of the following techniques would be most useful in this endeavor?

(A) Culture (B) Ribotyping (C) 16S rRNA sequencing (D) Antimicrobial susceptibility testing (E) Nucleic acid sequencing

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An unculturable gram-positive microorganism has been visualized in tissue specimens obtained from patients with a previously undescribed disease. Which of the following techniques would be most useful in identifying this organism?

(A) Serology (B) PCR amplification and sequencing of rRNA genes (C) Multilocus enzyme electrophoresis (D) SDS-polyacrylamide gel electrophoresis (E) Pulsed field gel electrophoresis

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The DNA polymerase from Thermus aquaticus is an important component of DNA amplification methods such as the polymerase chain reaction. This organism is capable of growing at temperatures above 100°C. Organisms that are capable of growth at these temperatures are referred to as

(A) Mesophiles (B) Psychrophiles (C) Halophiles (D) Thermophiles (E) Chemolithotrophs

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A 23-year-old woman has 10 Escherichia coli inoculated into her bladder while having sex. These E coli have a generation time of 20 minutes. After a lag of 20 minutes, the E coli enter the logarithmic phase of growth. After 3 hours of logarithmic growth, the total number of cells is

(A) 2560 (B) 5012 (C) 90 (D) 1028 (E) 1,000,000

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A 73-year-old woman is admitted to the hospital for intravenous treatment of an abscess caused by Staphylococcus aureus. Subsequent to her treatment and discharge from the hospital, it is necessary to disinfect the hospital room. One thousand of the S aureus cells are exposed to a disinfectant. After 10 minutes, 90% of the cells are killed. How many cells remain viable after 20 minutes?

(A) 500 (B) 100 (C) 10 (D) 1 (E) 0

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The action of which of the following agents or processes on bacteria can be reversed?

(A) A disinfectant (B) A bactericidal agent (C) A bacteriostatic agent (D) Autoclaving at 121°C for 15 minutes (E) Dry heat at 160–170°C for 1 hour

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The growth rate of bacteria during the exponential phase of growth is

(A) Zero (B) Increasing (C) Constant (D) Decreasing (E) Negative

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The growth rate of bacteria during the maximum stationary phase of growth is

(A) Zero (B) Increasing (C) Constant (D) Decreasing (E) Negative

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Most microorganisms pathogenic for humans grow best in the laboratory when cultures are incubated at

(A) 15–20°C (B) 20–30°C (C) 30–37°C (D) 38–50°C (E) 50–55°C

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The process by which microorganisms form ATP during the fermentation of glucose is characterized by

(A) Coupling of ATP production with the transfer of electrons (B) Denitrification (C) The reduction of oxygen (D) Substrate phosphorylation (E) Anaerobic respiration

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Which of the following culture techniques and media would enumerate the greatest number of microbial species in a soil sample?

(A) Enrichment culture (B) A plate of selective medium (C) A plate of differential medium (D) A tube of nutrient broth (E) A number of different media and conditions of incubation

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Polymerization of building blocks (eg, amino acids) into macromolecules (eg, proteins) is achieved largely by

(A) Dehydration (B) Reduction (C) Oxidation (D) Assimilation (E) Hydrolysis

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A strain of E coli undergoes a mutation such that it can no longer grow in a defined medium consisting of glucose, mineral salts, and ammonium chloride. However, it is capable of growth in this medium if methionine is added. The methionine is referred to as

(A) An inorganic salt (B) A sulfur source (C) A growth factor (D) An energy source (E) A nitrogen source

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Which of the following is NOT a mechanism for generating metabolic energy by microorganisms?

(A) Fermentation (B) Protein synthesis (C) Respiration (D) Photosynthesis (E) C and D

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Which of the following terms best describes a microorganisms that grows at 20°C?

(A) Neutralophile (B) Psychrotroph (C) Mesophile (D) Osmophile (E) Thermophile

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The ability to assimilate N2 reductively via NH3 is called

(A) Ammonification (B) Anammox (C) Assimilatory nitrate reduction (D) Deamination (E) Nitrogen fixation

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Which of the following is NOT assimilated by eukaryotic cells?

(A) Glucose (B) Lactate (C) Sulfate (SO4 2-) (D) Nitrogen (N2) (E) Phosphate (PO4 3-)

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Bacteria that are obligate intracellular pathogens of humans (eg, Chlamydia trachomatis) are considered to be

(A) Autotrophs (B) Photosynthetic (C) Chemolithotrophs (D) Hyperthermophiles (E) Heterotrophs

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The synthesis of which of the following cell components is dependent on a template?

(A) Lipopolysaccharide

(B) Peptidoglycan
(C) Capsular polysaccharide
(D) Deoxyribonucleic acid
(E) Phospholipids

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The synthesis of which of the following cell components is determined entirely by enzyme specificities?

(A) DNA
(B) Ribosomal RNA
(C) Flagella
(D) Lipopolysaccharide
(E) Protein

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The steps leading to the synthesis of peptidoglycan occur in the cytoplasm, on the cytoplasmic membrane, and extracellularly. Which antibiotic inhibits an extracellular step in peptidoglycan biosynthesis?

(A) Cycloserine
(B) Rifampin
(C) Penicillin
(D) Bacitracin
(E) Streptomycin

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Amino acids are found in the protein, peptidoglycan, and capsule of bacteria. Which of the following amino acids is found only in peptidoglycan?

(A) l-Lysine
(B) Diaminopimelic acid
(C) d-Glutamate
(D) l-Alanine (E) None of the above

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The ability to use compounds and ions other than oxygen as terminal oxidants in respiration is a widespread microbial trait. This capacity is called

(A) Photosynthesis
(B) Fermentation
(C) Anaerobic respiration
(D) Substrate phosphorylation (E) Nitrogen fixation

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The primary route of carbon assimilation used by organisms that can use CO2 as a sole source of carbon is (A) Hexose monophosphate shunt (B) Entner-Doudoroff pathway (C) Embden-Meyerhof pathway (D) Glyoxalate cycle (E) Calvin cycle

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The peptidoglycan biosynthetic pathway is of particular importance in medicine because it provides a basis for selective antibacterial action of several chemotherapeutic agents. All of the following antibiotics inhibit steps in peptidoglycan biosynthesis EXCEPT (A) Cycloserine (B) Vancomycin (C) Bacitracin (D) Streptomycin (E) Penicillin

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The regulation of enzyme activity provides fine control of metabolic pathways. Which of the following regulatory mechanisms provides fine control of a biosynthetic pathway? (A) Catabolite repression (B) Induction (C) Feedback inhibition (D) Attenuation (E) None of the above

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The biosynthetic origin of building blocks and coenzymes can be traced back to relatively few precursors called focal metabolites. Which of the following are focal metabolites? (A) a-Ketoglutarate (B) Oxaloacetate (C) Phosphoenolpyruvate (D) Glucose 6-phosphate (E) All of the above

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Which of the following is NOT a component of peptidoglycan? (A) N-Acetyl muramic acid (B) N-Acetyl glucosamine (C) Lipid A (D) Pentaglycine (E) Diaminopimelic acid

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Mutations in bacteria can occur by which of the following mechanisms? (A) Base substitutions (B) Deletions (C) Insertions (D) Rearrangements (E) All of the above

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The form of genetic exchange in which donor DNA is introduced to the recipient by a bacterial virus is (A) Transformation (B) Conjugation (C) Transfection (D) Transduction (E) Horizontal transfer

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The form of genetic exchange in bacteria that is most susceptible to the activity of deoxyribonuclease during the process of DNA uptake is (A) Transformation (B) Conjugation (C) Transfection (D) Transduction (E) All of the above

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Replication of which of the following requires physical integration with a bacterial replicon? (A) Single-stranded DNA bacteriophage (B) Double-stranded DNA bacteriophage (C) Single-stranded RNA bacteriophage (D) Plasmid (E) Transposon

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The formation of a mating pair during the process of conjugation in Escherichia coli requires (A) Lysis of the donor (B) A sex pilus (C) Transfer of both strands of DNA (D) A restriction endonuclease (E) Integration of a transposon

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A 22-year-old woman who works in a plant nursery presents with a history of fever and cough for 2 months. Over this period of time she has lost 5 kg. Chest radiography shows bilateral upper lobe infiltrates with cavities. A stain of her sputum shows acid-fast bacilli. The likely means by which the patient acquired her infection is (A) Sexual activity (B) Ingesting the microorganisms in her food (C) Holding onto contaminated hand rails when she takes public transportation (D) Handling potting soil (E) Breathing aerosolized droplets containing the microorganism

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During a pandemic of a well-characterized disease, a group of 175 airline passengers flew from Lima, Peru, to Los Angeles. Lunch on the plane included crab salad, which was eaten by about two-thirds of the passengers. After landing in Los Angeles, many of the passengers transferred to other flights with destinations in other parts of California and other Western states. Two of the passengers who stayed in Los Angeles developed severe watery diarrhea. The status of the other passengers was unknown. The likely cause of the diarrhea in the two passengers is (A) Escherichia coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7) (B) Vibrio cholerae type O139 (lipopolysaccharide O antigen 139) (C) Shigella dysenteriae type 1 (D) Campylobacter jejuni (E) Entamoeba histolytica

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A 65-year-old woman has a long-term central venous catheter for intravenous therapy. She develops fever and subsequently has multiple blood cultures positive for Staphylococcus epidermidis. All of the S epidermidis isolates have the same colony morphology and antimicrobial susceptibility pattern, suggesting that they are the same strain. A S epidermidis biofilm is thought to be present on the catheter. Which one of the following statements about such an infection is correct? (A) The biofilm containing the S epidermidis is likely to wash off the catheter. (B) Production of an extracellular polysaccharide inhibits growth of the S epidermidis, limiting the infection. (C) The S epidermidis in the biofilm are likely to be more susceptible to antimicrobial therapy because the bacteria have decreased rates of metabolism. (D) The quorum-sensing ability of S epidermidis results in increased susceptibility to antimicrobial therapy. (E) The complex molecular interactions within the biofilm make it difficult to provide effective antimicrobial therapy, and it is likely the catheter will have to be removed to cure the infection.

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The first microorganism to satisfy Koch’s postulates (in the late 19th century) was (A) Treponema pallidum (B) Stenotrophomonas maltophilia (C) Mycobacterium leprae (D) Bacillus anthracis (E) Neisseria gonorrhoeae

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Which of the following statements about lipopolysaccharide is correct? (A) It interacts with macrophages and monocytes yielding release of cytokines. (B) The toxic component is the O side chain. (C) It forms holes in red blood cell membranes yielding hemolysis. (D) It causes hypothermia. (E) It causes paralysis.

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A 27-year-old man had a rhinoplasty. A nasal tampon was placed to control the bleeding. Approximately 8 hours later, he developed headache, muscle aches, and abdominal cramps with diarrhea. He then developed an erythematous rash (resembling sunburn) over much of his body, including the palms and soles. His blood pressure is 80/50 mm Hg. The nasal tampon remained in place. His liver enzyme tests were elevated, and there was evidence of moderate renal failure. This patient’s illness was likely to be caused by which of the following? (A) Lipopolysaccharide (B) Peptidoglycan (C) A toxin that is a superantigen (D) A toxin that has A and B subunits (E) Lecithinase (alpha toxin)

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The organism most likely to be responsible for the patient’s disease (Question 6) is (A) Escherichia coli (B) Corynebacterium diphtheriae (C) Clostridium perfringens (D) Neisseria meningitidis (E) Staphylococcus aureus

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Which of the following is most likely to be associated with the formation of a bacterial biofilm? (A) Airway colonization in a cystic fibrosis patient with a mucoid (alginate-producing) strain of Pseudomonas aeruginosa (B) Urinary tract infection with Escherichia coli (C) Meningitis with Neisseria meningitidis (D) Tetanus (E) Impetigo caused by Staphylococcus aureus

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Regarding bacterial type III secretions systems, which of the following statements is correct? (A) They are commonly found in gram-positive commensal bacteria. (B) They play an important role in the pathogenesis of toxin-induced diseases of Clostridium species, tetanus, botulism, gas gangrene, and pseudomembranous colitis. (C) They cause release of effectors of pathogenesis into the extracellular environment, promoting bacterial colonization and multiplication. (D) They directly inject bacterial proteins into host cells across bacterial and host cell membranes, promoting pathogenesis of infections. (E) Mutations that prevent the bacterial type III secretion from functioning enhance pathogenesis

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Which of the following statements is correct? (A) Lipopolysaccharide is part of the cell wall of Escherichia coli. (B) Cholera toxin is attached to the flagella of Vibrio cholerae. (C) The lecithinase of Clostridium perfringens causes diarrhea. (D) Toxic shock syndrome toxin-1 is produced by hemolytic strains of Staphylococcus epidermidis.

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A 15-year-old Bangladeshi girl develops severe watery diarrhea. The stool looks like “rice water.” It is voluminous—more than 1 L in the last 90 minutes. She has no fever and seems otherwise normal except for the effects of loss of fluid and electrolytes. The most likely cause of her illness is (A) Clostridium difficile enterotoxin (B) A toxin with A and B subunits (C) Shigella dysenteriae type 1 that produces Shiga toxin (D) Enterotoxigenic Escherichia coli that produces heat-labile and heat-stable toxins (E) Staphylococcal enterotoxin F

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The most important thing that can be done to treat the patient (Question 11) is (A) To give her ciprofloxacin (B) To give her a toxoid vaccine (C) To give her the appropriate antitoxin (D) To treat her with fluid and electrolyte replacement (E) To culture her stool to make the correct diagnosis and then treat specifically

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A 23-year-old woman has a history of recurrent urinary tract infections, including at least one episode of pyelonephritis. Blood typing shows the P blood group antigen. Which of the following is likely to be the primary cause of her infections? (A) Escherichia coli that produce heat-stable toxin (B) Escherichia coli with K1 (capsular type 1) antigen (C) Escherichia coli O139 (lipopolysaccharide O antigen 139) (D) Escherichia coli with P-pili (fimbriae) (E) Escherichia coli O157:H7 (lipopolysaccharide O antigen 157; flagellar antigen 7)

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A 55-year-old man presents with gradually increasing weight loss, abdominal pain, diarrhea, and arthropathy. During the evaluation process, a small bowel biopsy is done. After processing, examination of the specimen by light microscopy reveals periodic acid-Schiff–positive inclusions in the bowel wall. Which of the following tests could be done to confirm the diagnosis of Whipple disease, caused by Tropheryma whipplei? (A) Culture on agar media (B) Polymerase chain reaction amplification and sequencing of an appropriate segment of DNA (C) Cocultivation with Escherichia coli (D) In situ hybridization (E) Direct fluorescent antibody test

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Which of the following best describes the mechanism of action of diphtheria toxin? (A) Forms pores in red blood cells causing hemolysis (B) Degrades lecithin in eukaryotic cell membranes (C) Causes release of tumor necrosis factor (D) Inhibits elongation factor 2 (E) Causes increased adenylate cyclase activity

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The synthesis of which of the following cell components is dependent on a template? (A) Lipopolysaccharide (B) Peptidoglycan (C) Capsular polysaccharide (D) Deoxyribonucleic acid (E) Phospholipids

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The synthesis of which of the following cell components is determined entirely by enzyme specificities? (A) DNA (B) Ribosomal RNA (C) Flagella (D) Lipopolysaccharide (E) Protein

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Amino acids are found in the protein, peptidoglycan, and capsule of bacteria. Which of the following amino acids is found only in peptidoglycan? (A) l-Lysine (B) Diaminopimelic acid (C) d-Glutamate (D) l-Alanine (E) None of the above

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The ability to use compounds and ions other than oxygen as terminal oxidants in respiration is a widespread microbial trait. This capacity is called (A) Photosynthesis (B) Fermentation (C) Anaerobic respiration (D) Substrate phosphorylation (E) Nitrogen fixation

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Which of the following is NOT a component of peptidoglycan? (A) N-Acetyl muramic acid (B) N-Acetyl glucosamine (C) Lipid A (D) Pentaglycine (E) Diaminopimelic acid

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Mutations in bacteria can occur by which of the following mechanisms? (A) Base substitutions (B) Deletions (C) Insertions (D) Rearrangements (E) All of the above

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The form of genetic exchange in which donor DNA is introduced to the recipient by a bacterial virus is (A) Transformation (B) Conjugation (C) Transfection (D) Transduction (E) Horizontal transfer

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A 26-year-old woman visits her physician because of an unusual vaginal discharge. On examination, the physician observes a thin, homogeneous, white-gray discharge that adheres to the vaginal wall. The pH of the discharge is 5.5 (normal, <4.3). On Gram stain, many epithelial cells covered with gram-variable rods are seen. Bacterial vaginosis is diagnosed. Which one of the following normal genital flora microorganisms is greatly decreased in bacterial vaginosis? (A) Corynebacterium species (B) Staphylococcus epidermidis (C) Prevotella species (D) Candida albicans (E) Lactobacillus species

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Certain microorganisms are never considered to be members of the normal flora. They are always considered to be pathogens. Which one of the following organisms fits into that category? (A) Streptococcus pneumoniae (B) Escherichia coli (C) Mycobacterium tuberculosis (D) Staphylococcus aureus (E) Neisseria meningitidis

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A 9-year-old girl develops fever and severe pain on the right side of her throat. On examination, redness and swelling in the right peritonsillar area are seen. A peritonsillar abscess is diagnosed. The most likely organisms to be cultured from this abscess are (A) Staphylococcus aureus (B) Streptococcus pneumoniae (C) Corynebacterium species and Prevotella melaninogenica (D) Normal oral nasal flora (E) Viridans streptococci and Candida albicans

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A 70-year-old man with a history of diverticulosis of the sigmoid colon experiences a sudden onset of severe left lower quadrant abdominal pain. Fever develops. The severe pain gradually subsides and is replaced by a constant aching pain and marked abdominal tenderness. A diagnosis of probable ruptured diverticulum is made, and the patient is taken to the operating room. The diagnosis of ruptured diverticulum is confirmed, and an abscess next to the sigmoid colon is found. The most likely bacteria to be found in the abscess are (A) Mixed normal gastrointestinal flora (B) Bacteroides fragilis alone (C) Escherichia coli alone (D) Clostridium perfringens alone (E) Enterococcus species alone

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Antimicrobial therapy can decrease the amount of susceptible bowel flora and allow proliferation of relatively resistant colonic bacteria. Which one of the following species can proliferate and produce a toxin that causes diarrhea? (A) Enterococcus species (B) Staphylococcus epidermidis (C) Pseudomonas aeruginosa (D) Clostridium difficile (E) Bacteroides fragilis

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Which one of the following microorganisms can be part of the normal vaginal flora and cause meningitis in newborns? (A) Candida albicans (B) Corynebacterium species (C) Staphylococcus epidermidis (D) Ureaplasma urealyticum (E) Group B streptococci

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Dental plaque and periodontal disease can be thought of as a continuum of what type of physiological process? (A) Biofilm formation (B) Normal aging (C) Abnormal digestion (D) Exaggerated immune response (E) Chewing gum

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Which one of the following microorganisms is closely associated with dental caries? (A) Candida albicans (B) Streptococcus mutans (C) Prevotella melaninogenica (D) Neisseria subflava (E) Staphylococcus epidermidis

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Anaerobic bacteria such as Bacteroides fragilis occur in the sigmoid colon in a concentration of about 1011/g of stool. At what concentration do facultative organisms such as Escherichia coli occur? (A) 1011/g (B) 1010/g (C) 109/g (D) 108/g (E) 107/g

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Streptococcus pneumoniae can be part of the normal flora of 5–40% of people. At what anatomic site can it be found? (A) Conjunctiva (B) Nasopharynx (C) Colon (D) Urethra (E) Vagina

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Hundreds of phylotypes have been identified in the human stomach; however, the only microorganism that has been shown to persist is (A) Lactobacillus casei (B) Lactobacillus acidophilus (C) Escherichia coli (D) Helicobacter pylori (E) Bifidobacteria

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Resident flora is commonly found in the (A) Liver (B) Urethra (C) Kidneys (D) Salivary glands (E) Gall bladder

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Resident flora is absent from the (A) Pharynx (B) Lungs (C) Small intestine (D) Synovial fluid (E) Conjunctiva

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A 65-year-old woman was admitted with squamous cell carcinoma of the cervix. She underwent extensive gynecologic surgery and was maintained postoperatively on broad-spectrum intravenous antibiotics. The patient had a central venous catheter placed on the day of surgery. Beginning 3 days postoperatively, the patient became febrile. On day 8, cultures of blood and of the tip of the central line both grew gram-positive organisms that were ovoid and reproduced by budding. Which of the following microorganisms is most likely responsible for the patient’s condition? (A) Staphylococcus aureus (B) Staphylococcus epidermidis (C) Enterococcus faecalis (D) Candida albicans (E) Saccharomyces cerevisae

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The most likely portal of entry for the organism in Question 14 is (A) During gynecologic surgery (B) Aspiration (C) During placement of the central line (D) During placement of IV line for administration of antibiotics (E) Intubation while under anesthesia

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A housewife who lives on a small farm is brought to the emergency department complaining of double vision and difficulty talking. Within the past 2 hours, she noted a dry mouth and generalized weakness. Last night she served home-canned green beans as part of the meal. She tasted the beans before they were boiled. None of the other family members are ill. On examination, there is symmetrical descending paralysis of the cranial nerves, upper extremities, and trunk. The correct diagnosis is which one of the following? (A) Tetanus (B) Strychnine poisoning (C) Botulism (D) Morphine overdose (E) Ricin intoxication

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Which one of the following is an important virulence factor of Bacillus anthracis? (A) Protective antigen (B) Lipopolysaccharide (C) Pili (D) A toxin that inhibits peptide chain elongation factor EF-2 (E) Lecithinase

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A young man sustains major soft tissue injury and open fractures of his right leg after a motorcycle accident. One day later, he has a temperature of 38°C, increased heart rate, sweating, and restlessness. On examination, the leg is swollen and tense, with thin, dark serous fluid draining from the wounds. The skin of the leg is cool, pale, white, and shining. Crepitus can be felt in the leg. His hematocrit is 20% (~50% of normal), and his circulating hemoglobin is normal. His serum shows free hemoglobin. Which of the following microorganisms is the most likely cause of this infection? (A) Clostridium tetani (B) Staphylococcus aureus (C) Escherichia coli (D) Bacillus anthracis (E) Clostridium perfringens

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For the patient described in Question 3, which of the following is likely to be responsible for the hemolysis? (A) EF (B) Tetanospasmin (C) Lecithinase (D) Streptolysin O (E) Toxin B

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The reported incubation period for inhalational anthrax can be up to (A) 2 days (B) 10 days (C) 3 weeks (D) 6 weeks (E) 6 months

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A food commonly associated with Bacillus cereus food poisoning is (A) Fried rice (B) Baked potato (C) Hot freshly steamed rice (D) Green beans (E) Honey

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Tetanus toxin (tetanospasmin) diffuses to terminals of inhibitory cells in the spinal cord and brainstem and blocks which of the following? (A) Release of acetylcholine (B) Cleavage of SNARE proteins (C) Release of inhibitory glycine and γ-aminobutyric acid (D) Release of PA (E) Activation of acetylcholine esterase

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A 45-year-old man who immigrated to the United States 5 years ago sustained a puncture injury to the lower part of his right leg when his rotary lawn mower threw a small stick into his leg. Six days later, he noticed spasms in the muscles of his right leg; on day 7, the spasms increased. Today—day 8—he had generalized muscle spasms, particularly noticeable in the muscles of his jaw. He was unable to open his jaw and came to the emergency department (ED). In the ED, you see a man who is alert and lying quietly in bed. A door slams down the hall, and suddenly he has general muscle spasm with arching of his back. The correct diagnosis is which of the following? (A) Botulism (B) Anthrax (C) Gas gangrene (D) Tetanus (E) Toxic shock syndrome

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Which of the following statements about tetanus and tetanus toxoid is correct? (A) Tetanus toxin kills neurons. (B) Tetanus toxoid immunization has a 10% failure rate. (C) The mortality rate of generalized tetanus is less than 1%. (D) Double vision is commonly the first sign of tetanus. (E) Tetanus toxin acts on inhibitor interneuron synapses.

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A 67-year-old man had surgery for a ruptured sigmoid colon diverticulum with an abscess. A repair was done, and the abscess was drained. He was treated with intravenous gentamicin and ampicillin. Ten days later and 4 days after being discharged from the hospital, the patient developed malaise, fever, and cramping abdominal pain. He had multiple episodes of diarrhea. His stool was positive for occult blood and the presence of polymorphonuclear cells. On sigmoidoscopy, the mucosa was erythematous and appeared to be inflamed, and there were many raised white to yellowish plaques 4–8 mm in diameter. Which of the following is the likely cause of the patient’s problem? (A) Staphylococcus aureus enterotoxin (B) Bacillus cereus toxin (C) Clostridium difficile toxins (D) Clostridium perfringens toxin (E) Enterohemorrhagic Escherichia coli

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Infant botulinum has been associated with all of the following Clostridium species except: (A) Clostridium baratii (B) Clostridium septicum (C) Clostridium butyricum (D) Clostridium botulinum

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Which of the following food items is most frequently associated with infant botulism? (A) Corn syrup (B) Canned infant formula (C) Liquid multivitamins (D) Honey (E) Jarred baby food

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All of the following are properties characteristic of Bacillus anthracis EXCEPT (A) Motility on wet mount examination (B) Medusa head colonies (C) Poly-d-glutamic acid capsule (D) In vitro susceptibility to penicillin (E) Absence of hemolysis on 5% sheep blood agar

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Which of the following statements regarding vaccination for Bacillus anthracis is correct? (A) It is routinely available for all citizens of the United States. (B) Recombinant vaccine trials have shown good safety and efficacy. (C) The current vaccine is well tolerated. (D) A single dose is adequate after exposure to spores. (E) Vaccination of animals is not useful.

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All of the following statements regarding Clostridium perfringens are correct EXCEPT (A) It produces an enterotoxin. (B) It produces a double zone of β-hemolysis when grown on blood agar. (C) Some strains are aerotolerant. (D) It is the most common cause of antibiotic-associated diarrhea. (E) It can cause intravascular hemolysis.

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Three months ago, a 53-year-old man underwent sigmoid colon resection for adenocarcinoma. He has had no evidence of recurrent cancer. He has noted a gradual decrease in sensation in his feet and lower legs. Examination today reveals a stocking-glove sensory deficit. The patellar reflex is absent, and the Achilles reflex is decreased bilaterally. Strength is normal. Which of the following is the most likely diagnosis? (A) Acute inflammatory demyelinating polyradiculoneuropathy (B) Subacute combined degeneration of the spinal cord (C) Multiple sclerosis (D) Alcoholic neuropathy (E) Radiation-induced brachial plexopathy

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Which of the following organisms most frequently causes septic arthritis in an alcoholic with cirrhosis? (A) Escherichia coli (B) Staphylococcus aureus (C) Streptococcus agalactiae (D) Pseudomonas aeruginosa (E) Pasteurella multocida

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Which of the following organisms is the most common cause of meningitis in a neonate? (A) Group B Streptococcus (B) Escherichia coli (C) Streptococcus pneumoniae (D) Neisseria meningitidis (E) Listeria monocytogenes

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A 48-year-old man is admitted to a hospital because of stupor. He is unkempt and homeless and lives in an encampment with other homeless people, who called the authorities when he could not be easily aroused. The patient drinks a lot of fortified wine and drank excessively 2 nights previously. His temperature is 38.5°C, and his blood pressure 125/80 mm Hg. He moans when attempts are made to arouse him. He has positive Kernig and Brudzinski signs, suggesting meningeal irritation. Physical examination and chest radiography show evidence of left lower lobe lung consolidation. An endotracheal aspirate yields rust-colored sputum. Examination of a Gram-stained sputum smear shows numerous polymorphonuclear cells and numerous gram-positive lancet-shaped diplococci. On lumbar puncture, the cerebrospinal fluid is cloudy and has a white blood cell count of 570/μL with 95% polymorphonuclear cells; Gram stain shows numerous gram-positive diplococci. Based on this information, the likely diagnosis is: A) Pneumonia and meningitis caused by Staphylococcus aureus B) Pneumonia and meningitis caused by Streptococcus pyogenes C) Pneumonia and meningitis caused by Streptococcus pneumoniae D) Pneumonia and meningitis caused by Enterococcus faecalis E) Pneumonia and meningitis caused by Neisseria meningitidis

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The patient in question 1 is started on antibiotic therapy to cover many possible microorganisms. Subsequently, culture of sputum and cerebrospinal fluid yields gram-positive diplococci with a minimum inhibitory concentration to penicillin G of greater than 2 μg/mL. The drug of choice for this patient until further susceptibility testing can be done is: A) Penicillin G B) Nafcillin E) Vancomycin

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This infection (question 1) might have been prevented by: A) Prophylactic intramuscular benzathine penicillin every 3 weeks B) A 23-valent capsular polysaccharide vaccine C) A vaccine against serogroups A, C, Y, and W135 capsular polysaccharide D) A vaccine of polyribosylribitol capsular polysaccharide covalently linked to a protein E) Oral penicillin twice daily

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The pathogenesis of the organism causing the infection (question 1) includes which of the following? A) Invasion of cells lining the alveoli and entry into the pulmonary venule circulation B) Resistance to phagocytosis mediated by M proteins C) Migration to mediastinal lymph nodes where hemorrhage occurs D) Lysis of the phagocytic vacuole and release into the circulation E) Inhibition of phagocytosis by a polysaccharide capsule

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A thirteen-valent capsular polysaccharide protein conjugate vaccine for the pathogen in question 1 is recommended: A) For children up to age 18 years and for selected adults B) Only on exposure to a patient with disease caused by the organism C) For children ages 2–23 months plus selected children through 59 months D) For children ages 24–72 months E) For all age groups older than age 2 months

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An 8-year-old boy develops a severe sore throat. On examination, a grayish-white exudate is seen on the tonsils and pharynx. The differential diagnosis includes group A streptococcal infection, Epstein-Barr virus infection, severe adenovirus infection, and diphtheria. (Neisseria gonorrhoeae pharyngitis would also be included, but the patient has not been sexually abused.) The cause of the boy’s pharyngitis is most likely: A) A catalase-negative gram-positive coccus that grows in chains B) A single-stranded positive-sense RNA virus C) A catalase-positive gram-positive coccus that grows in clusters D) A catalase-negative gram-positive bacillus E) A double-stranded RNA virus

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A primary mechanism responsible for the pathogenesis of the boy’s disease (question 6) is: A) A net increase in intracellular cyclic adenosine monophosphate B) Action of M protein C) Action of IgA1 protease D) Action of enterotoxin A E) Inactivation of elongation factor 2

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A 40-year-old woman develops severe headache and fever. Her neurologic examination findings are normal. A brain scan shows a ring-enhancing lesion of the left hemisphere. During surgery, a brain abscess is found. Culture of the abscess fluid grows an anaerobic gram-negative bacillus (Bacteroides fragilis) and a catalase-negative gram-positive coccus that on Gram stain is in pairs and chains. The organism is β-hemolytic and forms very small colonies (<0.5 mm in diameter). One person thought it smelled like butterscotch. It agglutinates with group F antisera. The organism most likely is: A) Streptococcus pyogenes (group A) B) Enterococcus faecalis (group D) C) Streptococcus agalactiae (group B) D) Streptococcus anginosus group E) Staphylococcus aureus

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The single most important method for classifying and speciating streptococci is: A) Agglutination using antisera against the cell wall group specific substance B) Biochemical testing C) Hemolytic properties (α-, β-, nonhemolytic) D) Capsular swelling (quellung) reaction E) None of the above

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An 8-year-old girl develops Sydenham’s chorea (“St. Vitus dance”) with rapid uncoordinated facial tics and involuntary purposeless movements of her extremities, strongly suggestive of acute rheumatic fever. She has no other major manifestations of rheumatic fever (carditis, arthritis, subcutaneous nodules, skin rash). The patient’s throat culture is negative for Streptococcus pyogenes (group A streptococci). However, she, her brother, and her mother all had sore throats 2 months ago. A test that if positive would indicate recent Streptococcus pyogenes infections is: A) Antistreptolysin S antibody titer B) Polymerase chain reaction for antibodies against M protein C) ASO antibody titer D) Esculin hydrolysis E) Antihyaluronic acid antibody titer

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All of the following statements regarding the hyaluronic acid capsule of Streptococcus pyogenes are correct except: A) It is responsible for the mucoid appearance of the colonies in vitro. B) It is antiphagocytic. C) It binds to CD44 on human epithelial cells. D) It is an important virulence factor. E) A vaccine against the capsule is currently available.

Enterococci can be distinguished from non-enterococcal group D streptococci on the basis of which of the following characteristics? A) γ-Hemolysis B) Esculin hydrolysis C) Growth in 6.5% NaCl D) Growth in the presence of bile E) Gram stain morphology

Which of the following statements regarding the Streptococcus bovis group is correct? A) They possess Lancefield group D antigen. B) Some strains are vancomycin resistant. C) Infections caused by these organisms are benign. D) All subspecies are PYR positive. E) All subspecies are β-hemolytic.

. Which of the following genera requires pyridoxal for growth? A) Aerococcus B) Granulicatella C) Enterococcus D) Leuconostoc E) Pediococcus

Which of the following genera is typically resistant to vancomycin? A) Aerococcus B) Gemella C) Pediococcus D) Streptococcus E) Abiotrophia

A 20-year-old college student goes to the student health center because of dysuria, frequency, and urgency on urination for 24 hours. She has recently become sexually active. On urinalysis, many polymorphonuclear cells are seen. The most likely organism responsible for these symptoms and signs is: (A) Staphylococcus aureus (B) Streptococcus agalactiae (C) Gardnerella vaginalis (D) Lactobacillus species (E) Escherichia coli

A 27-year-old woman is admitted to the hospital because of fever, with increasing anorexia, headache, weakness, and altered mental status of 2 days’ duration. She works for an airline as a cabin attendant, flying between the Indian subcontinent and other places in Southeast Asia and the West Coast of the United States. Ten days before admission, she had a diarrheal illness that lasted for about 36 hours. She has been constipated for the past 3 days. Her temperature is 39°C, heart rate is 68 beats/min, blood pressure is 120/80 mm Hg, and respirations are 18 breaths/min. She knows who she is and where she is but does not know the date. She is picking at the bedclothes. Rose spots are seen on her trunk. The remainder of the physical examination findings are normal. Blood cultures are done, and an intravenous line is placed. The most likely cause of her illness is: (A) Enterotoxigenic Escherichia coli (ETEC) (B) Shigella sonnei (C) Salmonella enterica subspecies enterica serotype Typhimurium (Salmonella Typhimurium) (D) Salmonella enterica subspecies enterica serotype Typhi (Salmonella Typhi) (E) Enteroinvasive Escherichia coli (EIEC)

Blood cultures from the patient in question 2 grow a non–lactose-fermenting gram-negative bacillus. Which of the following is likely to be a constituent of this organism? (A) O antigen 157, H antigen 7 (O157:H7) (B) Vi antigen (capsule; virulence antigen) (C) O antigen 139 (O139) (D) Urease (E) K1 (capsular type 1)

A 37-year-old woman with a history of urinary tract infections comes to the emergency department with burning on urination along with frequency and urgency. She says her urine smells like ammonia. The cause of her urinary tract infection is likely to be (A) Enterobacter aerogenes (B) Proteus mirabilis (C) Citrobacter freundii (D) Escherichia coli (E) Serratia marcescens

An 18-year-old student has abdominal cramps and diarrhea. A plate of MacConkey agar is inoculated and grows gram-negative rods. Triple sugar iron agar is used to screen the isolates for salmonellae and shigellae. A result suggesting one of these two pathogens would be (A) Production of urease (B) Motility in the medium (C) Inability to ferment lactose and sucrose (D) Fermentation of glucose (E) Production of gas in the medium

An uncommon serotype of Salmonella enterica subspecies enterica was found by laboratories in the health departments of adjacent states. The isolates were all from a small geographic area on either side of the border between the states, suggesting a common source for the isolates. (All of the isolates were from otherwise healthy young adults who smoked marijuana; the same Salmonella was isolated from a specimen of the marijuana.) By what method did the laboratories determine that these isolates were the same? (A) Capsular (K antigen) typing (B) O antigen and H antigen typing (C) DNA sequencing (D) Sugar fermentation pattern determination (E) Decarboxylase reaction pattern determination

A 43-year-old man with diabetes has a 4-cm nonhealing foot ulcer. Culture of the ulcer yields Staphylococcus aureus, Bacteroides fragilis, and a gram-negative bacillus that swarms across the blood agar plate covering the entire surface of the agar after 36 hours. The gram-negative bacillus is a member of the genus (A) Escherichia (B) Enterobacter (D) Salmonella (E) Proteus

A 4-year-old boy from Kansas City who recently started attending preschool and after-school daycare is brought to his pediatrician for a diarrheal illness characterized by fever to 38.2°C, severe lower abdominal pain, and initially watery diarrhea. His mother became concerned because the stools are now blood tinged 24 hours into the illness, and the child appears quite ill. The mother reports that two other children who attend the same after-school daycare have recently had diarrheal disease, one of whom likewise had bloody stools. Which of the following is the most likely pathogen causing the illness in these children? (A) An enterotoxigenic strain of Escherichia coli (B) Salmonella enterica subspecies enterica serotype Typhi (Salmonella Typhi) (C) Shigella sonnei (D) Edwardsiella tarda (E) Klebsiella oxytoca

A 5-year-old girl attended a birthday party at a local fast food restaurant. About 48 hours later, she developed cramping abdominal pain and a low-grade fever and had five episodes of loose, bloody stools. She is taken to a local emergency department the next evening because the diarrhea has continued, and she now appears pale and lethargic. On presentation, she has a temperature of 38°C, and she is hypotensive and tachycardic. The abdominal examination reveals tenderness in the lower quadrants. Laboratory work is remarkable for a serum creatinine of 2.0 mg/dL, a serum hemoglobin of 8.0 mg/dL, thrombocytopenia, and evidence of hemolysis. What is the most likely pathogen causing this child’s illness? (A) Escherichia coli O157:H7 (B) Salmonella enterica subspecies enterica serotype Typhimurium (C) Enteropathogenic Escherichia coli (D) Edwardsiella tarda (E) Plesiomonas shigelloides

A 55-year-old homeless man with alcoholism presents with severe multilobar pneumonia. He requires intubation and mechanical ventilation. A Gram stain of his sputum reveals numerous polymorphonuclear leukocytes and gram-negative rods that appear to have a capsule. The organism is a lactose fermenter on MacConkey agar and is very mucoid. It is nonmotile and lysine decarboxylase positive. What is the most likely organism causing this man’s illness? (A) Serratia marcescens (B) Enterobacter aerogenes (C) Proteus mirabilis (D) Klebsiella pneumoniae (E) Morganella morganii

Which of the following statements regarding O antigens is correct? (A) All Enterobacteriaceae possess identical O antigens. (B) They are found in the polysaccharide capsules of enteric bacteria. (C) They are covalently linked to a polysaccharide core. (D) They do not stimulate an immune response in the host. (E) They are not important in the pathogenesis of infection caused by enteric bacteria

Which of the following test methods is the least sensitive procedure for diagnosis of colitis caused by Shiga toxin–producing Escherichia coli? (A) Culture on sorbitol MacConkey agar (B) Toxin testing using an enzyme immunoassay (C) Cell culture cytotoxin assay using Vero cells (D) Polymerase chain reaction for detection of the genes that encode Shiga toxin

An HIV-positive man recently traveled to the Caribbean for a 2-week vacation. He developed acute watery diarrhea and abdominal pain without fever during the second week of his vacation. Three weeks later, he is seen in clinic for persistent symptoms, and he is concerned because he is beginning to lose weight. Given this history, you suspect: (A) Enteroinvasive E coli (B) Salmonella typhi (C) Enteropathogenic E coli (D) Shigella flexneri (E) Enteroaggregative E coli

Heat-labile toxin of ETEC acts by which of the following mechanisms? (A) Attachment and effacement (B) Activation of adenylyl cyclase (C) Aggregative adherence (D) Ribosomal dysfunction (E) None of the above

A young woman presents with recurrent urinary tract infections caused by the same Proteus mirabilis strain. What is the major concern? (A) She does not take her medication. (B) She is pregnant because pregnant patients are more susceptible to UTIs. (C) She has a bladder or kidney stone. (D) Her partner is infected. (E) She has occult diabetes and should have a glucose tolerance test.

A sputum culture of a patient with cystic fibrosis grows Pseudomonas aeruginosa that form very mucoid colonies. The implication of this observation is which one of the following? (A) The P aeruginosa are highly susceptible to the aminoglycoside antimicrobial tobramycin. (B) The P aeruginosa is infected with a pyocin (a bacteriocin). (C) The colonies are mucoid because they have polysaccharide capsule of hyaluronic acid. (D) The exotoxin A gene has been disabled and the P aeruginosa are no longer able to block host cell protein synthesis. (E) The P aeruginosa have formed a biofilm in the patient’s airway.

An environmental gram-negative bacillus that is resistant to cephalosporins, aminoglycosides, and quinolones has become a very important nosocomial pathogen largely because it is selected by use of those antibiotics. This gram-negative bacillus can take 2–3 days to grow and must be differentiated from Burkholderia cepacia. It is (A) Pseudomonas aeruginosa (B) Acinetobacter baumannii (C) Alcaligenes xylosoxidans (D) Klebsiella pneumoniae (E) Stenotrophomonas maltophilia

This gram-negative bacillus, which is oxidase positive and does not ferment carbohydrates, is frequently found in human bite infections. (A) Escherichia coli (B) Neisseria meningitidis (C) Chromobacterium violaceum (D) Eikenella corrodens (E) Proteus mirabilis

A 17-year-old girl with cystic fibrosis has a slight increase in her frequent cough and production of mucoid sputum. A sputum specimen is obtained and plated on routine culture media. The predominant growths are gram-negative bacilli that form very mucoid colonies after 48 hours of incubation. These bacilli are oxidase positive, grow at 42°C, and have a grapelike odor. These gram-negative bacilli are which of the following? (A) Klebsiella pneumoniae (B) Pseudomonas aeruginosa (C) Staphylococcus aureus (D) Streptococcus pneumoniae (E) Burkholderia cepacia

The sputum from the 17-year-old patient with cystic fibrosis (question 4) also is plated on mannitol salt agar, which turns yellow (from the baseline pink) where white colonies of gram-positive cocci are growing; the cocci are catalase positive and coagulase positive. The microorganisms growing on the mannitol salt agar are (A) Burkholderia cepacia (B) Streptococcus pneumoniae (C) Stenotrophomonas maltophilia (D) Staphylococcus aureus (E) Streptococcus pyogenes

The sputum from the 17-year-old patient with cystic fibrosis (question 4) also is plated on a colistin-containing agar. After 72 hours of incubation, the colistin-containing agar grows gram-negative bacilli that are oxidase positive but are otherwise difficult to identify. This microorganism is of major concern. It is sent to a reference laboratory so that molecular methods can be used to identify or rule out which of the following? (A) Pseudomonas aeruginosa (B) Burkholderia cepacia (C) Haemophilus influenzae (D) Pseudomonas putida (E) Burkholderia pseudomallei

When a Burkholderia cepacia complex organism is isolated from a patient with cystic fibrosis, great care must be taken in identifying the organism for which one of the following reasons? (A) B cepacia is commonly susceptible to penicillin G, but other similar gram-negative bacilli are not. (B) The presence of B cepacia complex in a CF patient’s airway has major implications for the patient’s long-term prognosis and therapeutic options. (C) Only B cepacia produces biofilms. (D) B cepacia complex produces an enzyme, sputolysase, which liquefies sputum, making it easier for the patient to cough and clear the airway. (E) Selective media for Pseudomonas aeruginosa commonly used for CF patients’ sputum cultures typically inhibit the B cepacia complex organisms, making it difficult to identify them.

Which of the following statements about Acinetobacter species is (are) true? (A) They are widespread in nature and in the hospital environment. (B) They are generally nonpathogenic to healthy individuals. (C) They may appear as gram-positive cocci. (D) They can mimic the morphology of Neisseria species in Gram stains of endocervical secretions to diagnose gonorrhea in women. (E) They can be a significant cause of ventilator-associated pneumonia in intensive care unit patients. (F) All of the above.

A 37-year-old firefighter sustains smoke inhalation and is hospitalized for ventilatory support. He has a severe cough and begins to expectorate purulent sputum. Gram stain of his sputum specimen shows numerous polymorphonuclear cells and numerous gram-negative rods. Sputum culture grows numerous gram-negative rods that are oxidase-positive. They grow well at 42°C. On clear agar medium, they produce a green color in the agar. The agar where the green color is located fluoresces when exposed to ultraviolet light. The organism causing the patient’s infection is (A) Pseudomonas aeruginosa (B) Klebsiella pneumoniae (C) Escherichia coli (D) Burkholderia cepacia (E) Burkholderia pseudomallei

The pigment produced by the microorganism in question 9 is (A) Aquamarine green (B) Aerobactin (C) Enterochelin (D) Pyoverdin (E) Prodigiosin

Burkholderia cepacia is infrequently found in or on (A) Swimming pools (B) Soil (C) Pond water (D) Plants

Which of the following statements about Pseudomonas aeruginosa is correct? (A) P aeruginosa are typically susceptible to penicillin G. (B) P aeruginosa are readily grown in anaerobic blood cultures. (C) P aeruginosa are able to penetrate intact normal human skin by elaborating the enzyme invasin. (D) P aeruginosa seldom, if ever, cause pneumonia. (E) P aeruginosa have fimbriae, which promote attachment to epithelial cells.

The mechanism of action of exotoxin A of Pseudomonas aeruginosa is (A) To activate acetylcholine esterase (B) To block elongation factor 2 (C) To form pores in white blood cells and increase cation permeability (D) To increase intracellular cyclic adenosine monophosphate (E) To split lecithin into phosphorylcholine and diacylglycerol

The HACEK bacteria sometimes cause indolent endocarditis or other infections. This acronym represents which of the following? (A) Cardiobacterium hominis (B) Eikenella corrodens (C) Kingella kingae (D) Aggregatibacter aphrophilus (formerly Haemophilus aphrophilus) (E) All of the above

A 30-year-old man, a dog owner, presents with fever to 39° C, hypotension, and early signs of disseminated intravascular coagulation. There is a left upper quadrant scar on physical examination, petechial lesions on the legs, and evidence of scratches from his dog on the arms and legs. Sepsis is suspected. The most likely pathogen is (A) Neisseria meningitides (B) Capnocytophaga canimorsus (C) Stenotrophomonas maltophilia (D) Alcaligenes species (E) Achromobacter species

Long-term carriage and shedding is most likely to occur after gastrointestinal infection with which of the following species? (A) Escherichia coli O157:H7 (B) Shigella dysenteriae (C) Vibrio cholerae (D) Campylobacter jejuni (E) Salmonella typhi

A 63-year-old man visited his favorite oyster restaurant in a small town on the eastern shore of the Gulf Coast of Texas. He ate two dozen oysters. Two days later, he was admitted to the hospital because of an abrupt onset of chills, fever, and lightheadedness when he stood up. (In the emergency department (ED), his blood pressure was 60/40 mm Hg.) While in the ED, he developed erythematous skin lesions. These rapidly evolved into hemorrhagic bullae, which then formed ulcers. The man drank a six-pack of beer and one half-bottle of whisky each day. A microorganism of major concern for this patient is (A) Vibrio vulnificus (B) Escherichia coli (C) Salmonella typhi (D) Clostridium perfringens (E) Streptococcus pyogenes (group A streptococci)

A 10-year-old boy was playing in a slowly moving stream when he cut his foot on a sharp object. Three days later he was brought to the emergency department because of pain and swelling at the site of the wound and drainage of pus from it. The most likely cause of the infection is (A) Vibrio vulnificus (B) Escherichia coli (C) Aeromonas hydrophila (D) Proteus mirabilis (E) Salmonella typhimurium

A family of four persons ate a meal that included undercooked chicken. Within 3 days, three members developed an illness characterized by fever, headache, myalgia, and malaise. Two of the patients had concomitant diarrhea and abdominal pain. The third person developed diarrhea after the systemic symptoms had cleared. Stool cultures grew Campylobacter jejuni. Which of the following culture conditions was most likely used to isolate C jejuni? (A) Thiosulfate-citrate-bile-sucrose medium incubated at 37°C in 5% oxygen and 10% CO2 (B) Salmonella-Shigella selective medium incubated at 37°C in ambient air (C) MacConkey agar and Hektoen enteric agar incubated at 42°C in 5% oxygen and 10% CO2 (D) 5% sheep blood agar incubated at 37°C in ambient air (E) A medium containing vancomycin, polymyxin B, and trimethoprim incubated at 42°C in 5% oxygen and 10% CO2

Bacteremia associated with a gastrointestinal infection is most likely to occur with which of the following? (A) Salmonella typhi (B) Vibrio cholerae (C) Shigella boydii (D) Vibrio parahaemolyticus (E) Campylobacter jejuni

During the El Niño years in the mid- to late 1990s, the waters of Puget Sound between Washington State and British Columbia warmed considerably. During this time, many people who ate clams and oysters from these waters became ill with a disease characterized by explosive diarrhea and moderately severe abdominal cramps. The diarrhea was usually watery, but in some patients, it was bloody. The diarrhea usually had an onset within 24 hours after eating the shellfish. Stool cultures typically yielded a pathogenic gram-negative bacillus. The microorganism of concern in this setting is (A) Enterotoxigenic Escherichia coli (B) Vibrio cholerae (C) Enterohemorrhagic Escherichia coli (D) Vibrio parahaemolyticus (E) Shigella dysenteriae

A patient presents to the emergency department with nonbloody diarrhea for 12 hours. The patient lives in Washington, DC, and has not recently traveled out of the area. Which one of the following is unlikely to be the cause of your patient’s diarrhea? (A) Salmonella typhimurium (B) Campylobacter jejuni (C) Shigella sonnei (D) Vibrio cholerae

An 18-year-old woman in rural Bangladesh develops profuse (8 L/d) diarrhea. She has no symptoms other than the diarrhea and the manifestations of the fluid and electrolyte loss caused by the diarrhea. The most likely cause of her diarrhea is (A) Campylobacter jejuni (B) Enterotoxigenic Escherichia coli (C) Salmonella typhimurium (D) Vibrio cholerae (E) Shigella dysenteriae

Age and geography are major factors in the prevalence of colonization by Helicobacter pylori. In developing countries, the prevalence of colonization may be greater than 80% in adults. In the United States, the prevalence of colonization with this microorganism in adults older than age 60 years is (A) 1–2% (B) 5–10% (C) 15–20% (D) 40–60% (E) 80–95%

A 59-year-old man comes to the emergency department in the afternoon because of acute swelling and pain in his right leg. Earlier that morning, he had been working on a small sport fishing boat in an estuary on the Gulf Coast of Texas. While walking around the boat in shallow water, he scratched his leg, breaking the skin at the site of the current pain and swelling. He was not wearing boots. About 1 hour after the injury, the scratch became red and painful. Swelling developed. Within 3 hours, the leg below the knee had become markedly swollen. The skin was red and tender. There was serous drainage from the wound, which had ulcerated and was now much enlarged. Near the wound, bullae were forming—the largest approximately 2.5 cm in diameter. The most likely cause of this medical emergency is (A) Staphylococcus aureus (B) Streptococcus pyogenes (C) Clostridium perfringens (D) Escherichia coli (E) Vibrio vulnificus

The Vibrio cholerae factor responsible for diarrhea is a toxin that (A) Blocks EF-2 (B) Yields increased intracellular levels of cAMP (C) Cleaves SNARE (D) Blocks EF-1-dependent binding of amino-acyl-tRNA to ribosomes (E) Cleaves VAMP

In September 1854, a severe epidemic of cholera occurred in the Soho/Golden Square area of London. Dr. John Snow, a father of epidemiology, studied the epidemic and helped stop it by which of the following actions? (A) Banning the sale of apples at the local markets (B) Removing the handle of the Broad Street water pump (C) Stopping the sale of shellfish imported from Normandy (D) Pasteurizing milk

A 45-year-old man develops a gastric ulcer that can be visualized on a contrast medium–enhanced radiograph of his stomach. A biopsy specimen is taken from the gastric mucosa at the site of the ulcer. A presumptive diagnosis can be reached most rapidly by inoculating part of the specimen on which of the following? (A) A medium used to detect urease incubated at 37°C (B) A medium containing vancomycin, polymyxin B, and trimethoprim incubated at 42°C (C) MacConkey agar medium incubated at 37°C (D) Thiosulfate-citrate-bile-sucrose medium incubated at 42°C (E) Blood agar medium incubated at 37°C

Which of the following is useful in differentiating Vibrio species from Aeromonas species? (A) Growth or no growth on a medium containing NaCl (B) The presence or absence on endotoxin in the cell wall. (C) Production or lack of production of a heat-labile enterotoxin (D) Positivity or negativity on the enterocyte invasion test

In the United States, public health officials often warn people to thoroughly cook chicken commercially obtained from supermarkets and stores. What percentage of chickens obtained from these sources are likely to be contaminated with Campylobacter jejuni? (A) 1–5% (B) 6–15% (C) 15–30% (D) 30–50% (E) Greater than 50%

An 18-year-old male resident of Arizona came to the emergency department (ED) complaining of fever, pain in his left groin, and diarrhea for the past 2 days. On examination, he was afebrile, had a pulse rate of 126 beats/min, a respiratory rate of 20 breaths/min, and a blood pressure of 130/80 mm Hg. Left groin swelling and tenderness were noted. A groin muscle strain was diagnosed, attributed to a fall 2 days earlier. He was treated with nonsteroidal anti-inflammatory drugs and released. The next day, the patient reported feeling weak, had difficulty breathing, and collapsed while taking a shower. He was transported to a hospital ED and pronounced dead shortly after arrival. Cultures of blood samples obtained in the ED were positive for Yersinia pestis. An epidemiologic investigation indicated that the patient most likely became infected as a result of bites by Yersinia pestis–infected fleas while walking through a prairie dog colony (see Chapter 48.) Which of the following statements about the pathogenesis of plague is correct? (A) Y pestis produces a coagulase when incubated at 28°C. (B) There is no risk for pneumonia caused by person-to-person transmission of Y pestis. (C) Y pestis organisms multiply in polymorphonuclear cells. (D) After the bite of an infected flea, Y pestis infection seldom, if ever, disseminates beyond the site of the flea bite and the regional lymph nodes. (E) Y pestis is transmitted to animals (and humans) in flea feces excreted when the flea is feeding.

The drug of choice to treat the patient in question 1 would have been (A) Ampicillin (B) Cefotaxime (C) Levofloxacin (D) Erythromycin (E) Streptomycin

Yersinia pestis entered North America through San Francisco in the 1890s, carried by rats on ships that had sailed from Hong Kong, where a plague epidemic occurred. The current reservoir for Y pestis in the United States is (A) Urban feral cats (B) Urban rats (C) Domestic cows (D) Coyotes (E) Rural wild rodents

Which of the following is generally not considered a potential agent of bioterrorism and biologic warfare? (A) Yersinia pestis (B) Botulinum toxin (C) Streptococcus pyogenes (D) Brucella species (E) Bacillus anthracis

An 8-year-old boy was bitten by a stray cat. Two days later, the wound was red and swollen and drained purulent fluid. Pasteurella multocida was cultured from the wound. The drug of choice to treat this infection is (A) Amikacin (B) Erythromycin (C) Gentamicin (D) Penicillin G (E) Clindamycin

Intimate contacts of patients with suspected plague pneumonia should receive which of the following agents as chemoprophylaxis? (A) Gentamicin (B) Cefazolin (C) Rifampin (D) Penicillin (E) Doxycycline

In a patient who has the bubonic form of plague, all of the following specimens are acceptable for diagnosis except (A) Stool culture on hektoen enteric agar (B) Blood culture using routine laboratory media (C) Culture of a lymph node aspirate on blood and MacConkey agars (D) Acute and convalescent serology (E) Immunohistochemical staining of lymph node tissue

All of the following statements regarding the pFra/pMT plasmid of Yersinia pestis are true except (A) It encodes the capsular protein (fraction FI) that confers antiphagocytic properties. (B) It contains genes that yield plasminogen-activating protease that has temperature-dependent coagulase activity. (C) It contains genes that encode phospholipase D, which is required for organism survival in the flea midgut. (D) It is unique to Y pestis. (E) It encodes factors that are important for survival in both the flea and the human.

All of the following statements regarding the epidemiology of infections caused by Yersinia enterocolitica are correct except (A) Most human infections are caused by serotype O:1. (B) Humans acquire the infection from ingestion of food or drinks contaminated by animals or animal products. (C) Person-to-person spread is quite common. (D) A large inoculum is required to cause infection. (E) Infection is more prevalent in persons with histocompatibility antigen HLA-B27.

Which of the following Pasteurella species has been associated with infections of the female genital tract and of newborns? (A) Pasteurella multocida (B) Pasteurella pneumotropica (C) Pasteurella ureae (D) Pasteurella bettyae

Optimum recovery of Yersinia enterocolitica from the stools of patients with gastroenteritis requires which of the following specialized media? (A) Cefsulodin-Irgasan-novobiocin agar (B) Xylose-lysine decarboxylase agar (C) Hektoen-enteric agar (D) Regan-Lowe medium (E) MacConkey agar

Which of the following organisms is likely to cause a transfusion reaction even if the donor is asymptomatic? (A) Pasteurella multocida (B) Escherichia coli (C) Pasteurella bettyae (D) Yersinia enterocolitica (E) None of the above

A 25-year-old graduate student is rushed to the operating room for fever, acute abdominal pain, and leukocytosis suggestive of acute appendicitis. During surgery, the appendix appears normal, but numerous, enlarged mesenteric lymph nodes are present. A likely diagnosis is (A) Epstein-Barr virus infection causing atypical infectious Mononucleosis (B) Mesenteric lymphadenitis caused by Y pseudotuberculosis (C) Gastrointestinal plague (D) An unusual presentation of shigellosis (E) Lymphadenitis caused by Pasteurella pneumotropica

A typical source of the infection in the case in question 13 is (A) Contact with the patient’s pet cat saliva (B) Accidental ingestion of prairie dog feces (C) Ingestion of contaminated water or food (D) Direct contact with another infected individual (E) Bite of an infected arthropod

An organism suspected of being Yersinia pestis is recovered from a patient with sepsis. The isolate has bipolar staining is catalase positive but is oxidase and urease negative and is non-motile. At this point, what should be done? (A) Nothing; the laboratory has confirmed the diagnosis. (B) Inoculate the isolate to an identification kit or automated system for confirmation. (C) Call the police because there is a possible bioterrorism event. (D) Send the isolate to the nearest public health laboratory for confirmation. (E) Send the isolate to the hospital across town for sequencing.

The inhabitants of a group of small villages in rural sub-Saharan Africa experienced an epidemic of meningitis. Ten percent of the people died, most of them younger than the age of 15 years. The microorganism that most likely caused this epidemic was (A) Streptococcus agalactiae (group B) (B) Escherichia coli K1 (capsular type 1) (C) Haemophilus influenzae serotype b (D) Neisseria meningitidis serogroup A (E) West Nile virus

A 19-year-old man presented to the clinic with a urethral discharge for the past 24 hours. Neisseria gonorrhoeae was cultured from the specimen and found to be β-lactamase positive and resistant to high levels (≥32 μg/mL) of tetracycline. Which of the following statements about these antimicrobial resistance factors is correct? (A) β-lactamase production and high-level resistance to tetracycline are both mediated by genes on plasmids. (B) Whereas β-lactamase production is mediated by a gene on the bacterial chromosome, high-level tetracycline resistance is mediated by a gene on a plasmid. (C) Whereas β-lactamase production is mediated by a gene on a plasmid, high-level tetracycline resistance is mediated by a gene on the bacterial chromosome. (D) β-lactamase production and high-level resistance to tetracycline are both mediated by genes on the bacterial chromosome.

A 6-year-old boy develops a fever and headache. He is taken to the emergency department, where he is noted to have a stiff neck, suggesting meningeal irritation. A lumbar puncture is done, and culture of the cerebrospinal fluid grows Neisseria meningitidis serogroup B. Which of the following should be considered for his family (household) members? (A) No prophylaxis or other steps are necessary. (B) They should be given N meningitidis pilin vaccine. (C) They should be given N meningitidis serogroup B polysaccharide capsule vaccine. (D) They should be given rifampin prophylaxis. (E) They should be given sulfonamide prophylaxis.

An 18-year-old woman who reports unprotected sex with a new partner 2 weeks previously develops fever and left lower quadrant abdominal pain with onset in association with her menstrual period. On pelvic examination in the emergency department, she has bilateral tenderness when the uterus is palpated. A mass 2–3 cm in diameter is felt on the left, suggestive of tubo-ovarian abscess. Subsequently, Neisseria gonorrhoeae is cultured from her endocervix. The diagnosis is gonococcal pelvic inflammatory disease. A common sequela of this infection is (A) Cancer of the cervix (B) Urethral stricture (C) Uterine fibroid tumors (D) Infertility (E) Vaginal-rectal fistula

A 38-year-old vice squad police officer comes to the emergency department with a chief complaint expressed as follows: “I have disseminated gonococcal infection again.” He is correct. Cultures of his urethra and knee fluid yield Neisseria gonorrhoeae. He has previously had five episodes of disseminated gonococcal infection. The patient should be evaluated for (A) Selective IgA deficiency (B) A polymorphonuclear cell chemotactic defect (C) Deficiency of a late-acting complement component C5, C6, C7, or C8 (D) Absent lymphocyte adenosine deaminase activity (E) Myeloperoxidase deficiency

Which of the following individuals should routinely receive vaccination with the conjugate meningococcal vaccine? (A) A healthy young adolescent entering high school (B) A healthy child entering kindergarten (C) A 60-year-old man with insulin-dependent diabetes (D) A healthy 40-year-old technician who works in a cancer research laboratory (E) A 65-year-old woman with coronary artery disease

A 25-year-old sexually active woman presents with purulent vaginal discharge and dysuria 7 days after having unprotected sexual intercourse with a new partner. Of the choices below, what is the most sensitive diagnostic method for determining the likely etiologic agent? (A) Gram stain (B) An enzyme immunoassay (C) Bacterial culture on selective media (D) A nucleic acid amplification test (E) Serology

What is the currently recommended treatment for gonococcal urethritis in men who have sex with men in the United States? (A) Single dose of an oral fluoroquinolone (B) Seven days of oral doxycycline (C) Ceftriaxone given intramuscularly as a single dose (D) Spectinomycin given intramuscularly as a single dose (E) Seven days of oral amoxicillin

Which of the following cell components produced by Neisseria gonorrhoeae is responsible for attachment to host cells? (A) Lipooligosaccharide (B) Pili (fimbriae) (C) IgA1 protease (D) Outer membrane porin protein (E) Iron-binding protein

A 60-year-old man with severe chronic lung disease presents with fever, cough productive of purulent sputum, and worsening hypoxemia. A sputum sample is collected, and the specimen is sent promptly to the laboratory. Microscopic examination of a Gram stain reveals numerous polymorphonuclear leukocytes and predominately gram-negative diplococci that are both intracellular and extracellular. The organism grows well on 5% SBA and chocolate agar and is positive for butyrate esterase. What is the most likely organism causing this man’s illness? (A) Neisseria gonorrhoeae (B) Neisseria lactamica (C) Moraxella catarrhalis (D) Haemophilus influenzae (E) Neisseria meningitidis

One major advantage of the conjugate meningococcal vaccines compared with the polysaccharide vaccine is (A) Stimulation of mucosal secretory IgA (B) Fewer side effects (C) A T cell–dependent response to vaccine is induced (D) Inclusion of serogroup B

A 25-year-old woman presents with septic arthritis of the knee. The fluid aspirate grows a gram-negative diplococcus on chocolate agar after 48 hours of incubation. The isolate is oxidase positive and oxidizes glucose but not maltose, lactose, or sucrose. You suspect infection with (A) Neisseria meningitidis (B) Neisseria lactamica (C) Moraxella catarrhalis (D) Neisseria gonorrhoeae (E) None of the above

All of the following are virulence factors associated with N gonorrhoeae except (A) Pili (B) Por (C) Lipooligosaccharide (D) Opa proteins (E) A thick polysaccharide capsule

The prevalence of gonococcal infections increased between 2009 and 2010. (A) True (B) False

A useful test to differentiate Moraxella catarrhalis from saprophytic neisseriae in respiratory samples is (A) Butyrate esterase (B) Gram stain (C) Growth on 5% sheep blood agar (D) PYR (E) Oxidase

A 55-year-old man visits his physician complaining of a severe cough and production of purulent sputum. His breath has a very unpleasant fetid odor. Chest radiography shows a large amount of fluid in the left pleural space and a 5-cm lung cavity with an air-fluid level. A needle is inserted through the chest wall, and some of the fluid in the pleural space is removed; it is thick, yellow-gray in color, and malodorous. Which of the following organisms or sets of organisms are most likely to be cultured from the pleural fluid? (A) Bacteroides fragilis, Escherichia coli, and enterococci (B) Prevotella bivia, peptostreptococci, and Staphylococcus epidermidis (C) Prevotella melaninogenica, Fusobacterium species, and viridans streptococci (D) Propionibacterium species, peptostreptococci, and Staphylococcus aureus (E) Streptococcus pneumoniae

A 23-year-old man develops a perirectal abscess, which is drained surgically. A specimen is cultured and grows anaerobic bacteria. Clues that suggest infection with anaerobic bacteria include (A) Negative aerobic culture results (B) Gas in tissues (C) Proximity to the mucosal surface (D) Foul-smelling discharge (E) All of the above

A 63-year-old man with diabetes routinely injects insulin into the muscles of his left thigh. He has recently developed severe pain with swelling in his left thigh. On examination, his thigh is swollen and red. Crepitus is noted on palpation, indicating gas in the tissue. Gas also is visible in the fascial planes on radiography of the leg. Gas gangrene caused by Clostridium perfringens is considered a likely diagnosis. What other infections must be considered? (A) Anaerobic streptococcal myonecrosis (B) Synergistic nonclostridial anaerobic myonecrosis (D) Aeromonas hydrophila myonecrosis (E) All of the above

An 18-year-old man develops fever with pain in the right lower quadrant of his abdomen. After initial evaluation, he is taken to the operating room. During surgery, a ruptured appendix with an abscess is found. Bacteroides fragilis is cultured from the abscess fluid. Which of the following factors promote abscess formation by B fragilis? (A) Lipopolysaccharide (B) Capsule (C) Superoxide dismutase (D) Pili (E) Leukocidin toxin

Infections caused by Bacteroides species can be treated with all of the following antibiotics except (A) Ampicillin–sulbactam (B) Clindamycin (C) Metronidazole (D) Penicillin (E) Cefoxitin

A 17-year-old high school senior develops infectious mononucleosis. About 2 weeks later, he develops a significantly higher fever, a worsening sore throat, an inability to swallow, and severe neck and chest pain. Upon admission, he has signs of sepsis and respiratory distress. What is the most likely organism causing this complication? (A) Fusobacterium necrophorum (B) Bacteroides ovatus (C) Prevotella melaninogenica (D) Clostridium tetani (E) Actinomyces israelii

Which of the following statements regarding Lactobacilli is correct? (A) They are anaerobic gram-positive cocci. (B) They are most commonly found in the oral cavity. (C) The major product of metabolism is propionic acid. (D) They rarely cause disease in humans. (E) They form endospores.

Which of the following statements best describes the pathogenesis of Clostridium botulinum? (A) It elaborates a toxin that inhibits the release of acetylcholine at cholinergic synapses. (B) It elaborates an exotoxin that is a lecithinase that causes tissue necrosis. (C) It produces a polysaccharide capsule that inhibits phagocytosis and contributes to invasion of the central nervous system. (D) It elaborates a toxin that suppresses the release of inhibitory neurotransmitters. (E) It produces a leukotoxin that leads to abscess formation.

The drug of choice for treatment of infections caused by Actinomyces species is (A) Tigecycline (B) Cefoxitin (C) Metronidazole (D) Imipenem (E) Penicillin

Infections commonly caused by Clostridium perfringens include all of the following except (A) Gas gangrene (B) Lumpy jaw (C) Food poisoning (D) Bacteremia

All of the following statements regarding anaerobes are true except (A) They possess the enzyme cytochrome oxidase (B) Many species are part of the normal human microbiota (C) They are often found along with aerobes in complicated infections (D) Special techniques are required to ensure their recovery from clinical specimens

Lemierre’s disease is a serious infection of the head and neck associated with which of the following anaerobes? (A) Prevotella melaninogenica (B) Bacteroides thetaiotamicron (C) Porphyromonas gingivalis (D) Peptococcus niger (E) Fusobacterium necrophorum

Definitive identification of an anaerobe is likely best accomplished by (A) Colony morphology on anaerobic media (B) The presence of pigment (C) Susceptibility to a variety of antimicrobial disks (D) Cell wall fatty acid analysis using gas liquid chromatography (E) None of the above

A patient who has not maintained good dentition presents with induration and swelling of the mandibular area. On examination, you note purulent material draining from a small opening. The material appears yellowish, and there are some visible granules. You perform a Gram stain, and pleomorphic gram-positive rods with short branches are noted along with cells suggestive of acute and chronic inflammation. You suspect which of the following organisms? (A) Bacteroides fragilis (B) Lactobacillus acidophilus (C) Clostridium perfringens (D) Actinomyces israelii (E) Eggerthella lenta

The recommended treatment in the non-allergic patient for the condition caused by the organism in question 14 is (A) Ampicillin (B) Cefoxitin (C) Imipenem (D) Clindamycin (E) Vancomycin

Humans become infected with Legionella pneumophila by (A) Drinking water contaminated with Acanthamoeba castellani containing Legionella pneumophila (B) Kissing a person who is a legionella carrier (C) Breathing aerosols from environmental water sources (D) Receiving a mosquito bite (E) Consuming undercooked pork

An 11-year-old girl developed an acute onset of fever, chills, headache, vomiting, and severe migratory arthralgias (joint pain) and myalgias (muscle pain). Two days later, she developed a maculopapular rash over her palms, soles, and extremities. At the same time, her left knee became extremely painful and swollen. On examination, fluid was demonstrated in the knee. Further history disclosed that the patient had a pet rat that she frequently played with. Culture of the fluid from her knee on 5% sheep blood agar showed 2-mm colonies after 3 days of incubation. Broth culture showed small puffball-like growth. Gram staining showed a gram-negative bacillus 0.5 μm wide and 1–4 μm long. Some extremely long forms (up to 150 μm) with beadlike chains, fusiform swellings, and large round bodies were seen. The microbiologist who observed the Gram-stained smear immediately knew the cause of the girl’s infection to be (A) Treponema pallidum (B) Streptobacillus moniliformis (C) Francisella tularensis (D) Bartonella bacilliformis (E) Yersinia pestis

A 70-year-old man presents with bilateral pneumonia. His Legionella urinary antigen test result is positive. Which of the following is the likely cause of his pneumonia? (A) Legionella pneumophila serogroup 1 (B) Legionella micdadei serogroup 4 (C) Legionella bozemanii serogroup 2 (D) Legionella longbeachae serogroup 2 (E) All of the above because the urinary antigen test is genus specific and not species or serotype specific

A 70-year-old man comes to the emergency department feeling feverish and “really tired.” He has a chronic cigarette cough, but this has dramatically increased in the past week and has been producing whitish sputum. The previous day he had a temperature of 38°C and watery diarrhea. Physical examination reveals inspiratory and expiratory wheezes and rales over the right lower lung field. Chest radiography shows a patchy right lower lobe infiltrate. The differential diagnosis of this patient’s disease is (A) Streptococcus pneumoniae pneumonia (B) Legionella pneumophila pneumonia (C) Haemophilus influenzae pneumonia (D) Mycoplasma pneumoniae pneumonia (E) All of the above

Routine sputum cultures for the patient in question 5 grow normal flora. Treatment with ampicillin for 2 days yields no improvement. A diagnosis of Legionnaires’ disease is considered, and bronchoscopy is done to obtain bronchial alveolar lavage fluid and deep airway specimens. Which of the following would suggest a diagnosis of disease caused by Legionella pneumophila serotype 1? (A) Legionella urinary antigen assay (B) Direct fluorescent antibody on the bronchial alveolar lavage fluid (C) Culture of the bronchial alveolar lavage on charcoal yeast extract medium with antibiotics (D) Antibody assay on paired (acute phase and convalescent phase) sera (E) All of the above

Charcoal is present in buffered charcoal yeast extract agar used to isolate Legionella pneumophila to (A) Provide the growth factors ordinarily provided by free-living amebas present in environmental water (B) Serve as a carbon source for the growth of Legionella pneumophila (C) Prevent hemolysis of the red blood cells in the medium (D) Provide a dark background (E) Act as a detoxifying agent

A 23-year-old woman presents with a 3-day history of low-grade fever and headache. Examination reveals enlarged and slightly tender lymph nodes near her left elbow and in the left axilla. Approximately 2 weeks earlier, she had visited a friend whose cat had scratched her on the left arm; the site later developed a reddish papule. Which of the following statements about cat-scratch disease is most correct? (A) The diagnosis is based on a suggestive history and physical examination. (B) The diagnosis is based on negative routine bacterial cultures of pus aspirated from involved lymph nodes. (C) The disease is usually self-limited in immunocompetent people. (D) The etiologic agent is Bartonella henselae. (E) All of the above.

Which of the following statements about bacillary angiomatosis is most correct? (A) It is caused by Bartonella bacilliformis. (B) It is typically confined to the skin. (C) The major differential diagnosis is Kaposi sarcoma. (D) The etiologic agent can be grown in 1–2 days in routine culture on sheep blood agar. (E) Dogs are the reservoir for the etiologic agent.

An important factor in the pathogenesis of Legionnaires’ disease is that (A) Legionella pneumophila kills polymorphonuclear cells. (B) Alveolar macrophages phagocytose Legionella pneumophila using coiled pseudopods. (C) Legionella pneumophila invades pulmonary capillaries, leading to dissemination and systemic illness. (D) Legionella pneumophila induces alveolar macrophage phagosomes to fuse with lysosomes. (E) Legionella pneumophila outer surface protein A (OspA) is important for invasion of alveolar macrophages.

True statements regarding T whipplei include all of the following except (A) It is easy to cultivate on chocolate agar after 3 days of incubation. (B) It is a gram-positive Actinomycete. (C) It causes fever, abdominal pain, diarrhea, weight loss, and migratory polyarthralgia. (D) It stains with PAS.

All of the statements below regarding infections with Legionella are correct except (A) Hospitals that care for patients at risk for Legionella infections should know if their potable water systems contain Legionella. (B) Human-to-human transmission is the major mechanism of transmission of Legionella infection. (C) Legionella species can be visualized with Gram stain if carbol fuchsin is used for the counterstain. (D) The chest radiograph of a patient who has Legionella pneumonia is indistinguishable from that of patients with pneumonia caused by other pathogens. (E) A macrolide or quinolone are the drugs of first choice for treatment of Legionella infections.

Which of the following best represents the role of the Mip protein in Legionella pathogenesis? (A) It prevents phagosome–lysosome fusion. (B) It acts as a siderophore to capture iron. (C) It prevents phagocytosis. (D) It facilitates adherence to the macrophage and stimulates cellular invasion. (E) None of the above.

Pontiac fever is a severe form of pneumonia caused by Legionella pneumophila serotypes 1 and 6. (A) True (B) False

All of the following statements regarding Streptobacillus moniliformis are correct except (A) It is susceptible to penicillin. (B) It causes the disease rat-bite fever. (C) It causes Haverhill fever from ingestion of contaminated food. (D) The morphology of the organism is spiral-shaped.

The diagnosis of Whipple’s disease is best made by (A) Paired serum obtained 8 weeks apart (B) Prolonged culture on mycobacterial media (C) Nucleic acid amplification testing performed on tissue (D) Histopathology (E) None of the above

A 60-year-old-man has a 5-month history of progressive weakness and a weight loss of 13 kg along with intermittent fever, chills, and a chronic cough productive of yellow sputum, occasionally streaked with blood. A sputum specimen is obtained, and numerous acid-fast bacteria are seen on the smear. Culture of the sputum is positive for Mycobacterium tuberculosis. Which treatment regimen is most appropriate for initial therapy? (A) Isoniazid and rifampin (B) Sulfamethoxazole–trimethoprim and streptomycin (C) Isoniazid, rifampin, pyrazinamide, and ethambutol (D) Isoniazid, cycloserine, and ciprofloxacin (E) Rifampin and streptomycin

If the patient’s Mycobacterium tuberculosis isolate (question 1) proves to be resistant to isoniazid, the likely mechanism for resistance is (A) β-lactamase (B) Mutations in the catalase-peroxidase gene (C) Alterations in the β subunit of RNA polymerase (D) Mutations in the DNA gyrase gene (E) Mutations in the genes encoding the S12 protein and 16S rRNA

A 47-year-old woman presents with a 3-month history of progressive cough, weight loss, and fever. Chest radiography shows bilateral cavitary disease suggestive of tuberculosis. Sputum culture grows an acid-fast bacillus that is a photochromogen (makes an orange pigment when exposed to light). The organism most likely is (A) Mycobacterium tuberculosis (B) Mycobacterium kansasii (C) Mycobacterium gordonae (D) Mycobacterium avium complex (E) Mycobacterium fortuitum

A 31-year-old Asian woman is admitted to the hospital with a 7-week history of increasing malaise, myalgia, nonproductive cough, and shortness of breath. She has daily fevers of 38–39°C and a recent 5-kg weight loss. She had a negative chest radiograph when she entered the United States 7 years ago. The patient’s grandmother died of tuberculosis when the patient was an infant. A current chest radiograph is normal; results of other tests show a decreased hematocrit and liver function test abnormalities. Liver and bone marrow biopsies show granulomas with giant cells and acid-fast bacilli. She is probably infected with (A) Mycobacterium leprae (B) Mycobacterium fortuitum (C) Mycobacterium ulcerans (D) Mycobacterium gordonae (E) Mycobacterium tuberculosis

It is very important that the patient in question 4 also be evaluated for (A) HIV/AIDS (B) Typhoid fever (C) Liver abscess (D) Lymphoma (E) Malaria

Of concern regarding the patient in question 4 is that she could be infected with a mycobacterium that is (A) Susceptible only to isoniazid (B) Resistant to streptomycin (C) Resistant to clarithromycin (D) Susceptible only to ciprofloxacin (E) Resistant to isoniazid and rifampin

You observe a 40-year-old man begging on a street in a town in India. He has clawing of the fourth and fifth digits with loss of distal parts of the digits of both hands, strongly suggesting leprosy. The causative agent of this disease (A) Is susceptible to isoniazid and rifampin (B) Grows in parts of the body that are cooler than 37°C (C) Can be cultured in the laboratory using Middlebrook 7H11 medium (D) Is seen in high numbers in biopsies of tuberculoid leprosy lesions (E) Commonly infects people in Texas because armadillos are hosts of Mycobacterium leprae

Which of the following statements about the purified protein derivative (PPD) and the tuberculin skin test is most correct? (A) It is strongly recommended that medical and other health science students have PPD skin tests every 5 years (B) Persons immunized with BCG rarely, if ever, convert to positive PPD skin test results. (C) The intradermal skin test is usually read 4 hours after being applied. (D) A positive tuberculin test result indicates that an individual has been infected with Mycobacterium tuberculosis in the past and may continue to carry viable mycobacteria. (E) A positive PPD skin test result implies that a person is immune to active tuberculosis.

A 72-year-old woman has an artificial hip joint placed because of degenerative joint disease. One week after the procedure, she has fever and joint pain. The hip is aspirated, and the fluid is submitted for routine culture and for culture for acid-fast organisms. After 2 days of incubation, there is no growth on any of the media. After 4 days, however, bacilli are seen growing on the sheep blood agar plate, and similar-appearing acid-fast bacilli are growing on the culture for acid-fast bacteria. The patient is most likely infected with (A) Mycobacterium tuberculosis (B) Mycobacterium chelonae (C) Mycobacterium leprae (D) Mycobacterium kansasii (E) Mycobacterium avium complex

A 10-year-old child has a primary pulmonary Mycobacterium tuberculosis infection. Which of the following features of tuberculosis is most correct? (A) In primary tuberculosis, an active exudative lesion develops and rapidly spreads to lymphatics and regional lymph nodes. (B) The exudative lesion of primary tuberculosis often heals slowly. (C) If tuberculosis develops years later, it is a result of another exposure to M tuberculosis. (D) In primary tuberculosis, all of the infecting M tuberculosis organisms are killed by the patient’s immune response. (E) In primary tuberculosis, the immune system is primed, but the PPD skin test result remains negative until there is a second exposure to M tuberculosis.

Which of the following statements regarding interferon-gamma release assays is correct? (A) They are useful for evaluating immunocompromised patients for active tuberculosis. (B) They detect antigens present in all Mycobacterium species. (C) They are not available yet for testing in the United States. (D) They are performed using molecular probes that detect organism DNA. (E) They are used as alternatives to the tuberculin skin test to evaluate for latent tuberculosis.

Mycobacterium abscessus most often causes pulmonary disease among which group of individuals? (A) Young children exposed to dirt (B) African American smokers (C) Elderly, nonsmoking white females (D) Hispanic men who work outdoors (E) Persons living in the Northwestern United States

A newly characterized rapidly growing mycobacterium that has emerged as an important cause of central venous catheter-associated infections is (A) Mycobacterium phlei (B) Mycobacterium mucogenicum (C) Mycobacterium xenopi (D) Mycobacterium smegmatis (E) Mycobacterium terrae

The definition of extensively drug-resistant (XDR) tuberculosis includes (A) Resistance to isoniazid (B) Resistance to a fluoroquinolone (C) Resistance to capreomycin, amikacin, or kanamycin (D) Resistance to rifampin (E) All of the above

All of the following organisms are rapidly growing mycobacteria except (A) Mycobacterium fortuitum (B) Mycobacterium abscessus (C) Mycobacterium mucogenicum (D) Mycobacterium nonchromogenicum (E) Mycobacterium chelonae

A 28-year-old woman who is 10 weeks pregnant presents to the obstetrics clinic for prenatal care. She has a history of treatment for syphilis 7 years previously. The results of serologic tests for syphilis are as follows: nontreponemal test, RPR, nonreactive; treponemal test (TP-PA), reactive. Which of the following statements is most correct? (A) The mother’s previous treatment for syphilis was effective. (B) The baby is at high risk for congenital syphilis. (C) The mother needs to be treated again for syphilis. (D) The mother needs a lumbar puncture and a VDRL test of her CSF for neurosyphilis.

Infections with which of the following agents can result in a false-positive nontreponemal (VDRL or RPR) test result for syphilis? (A) Lupus erythematosus (B) Measles (C) Leprosy (D) Pregnancy (E) Blood transfusions (F) Malaria (G) All of the above

A 20-year-old woman presents with a 2-cm ulcer on her labia majora. The lesion has a raised border and is relatively painless. What is the most likely pathogen? (A) Adenovirus infection (B) Papilloma virus infection (C) Neisseria gonorrhoeae infection (D) Chlamydia trachomatis cervicitis (E) Treponema pallidum infection

A 42-year-old woman went camping in the Sierra Nevada Mountains, where she slept for two nights in an abandoned log cabin. After the second night, a tick was found on her shoulder. Six days later, she developed fever to 38°C, which lasted for 4 days. Ten days later, she had another similar episode of fever. Examination of a blood smear stained with Wright stain showed spirochetes suggestive of Borrelia species. Which of the following statements about relapsing fever and Borrelia hermsii is correct? (A) Each relapse is associated with an antigenically distinct variant. (B) Blood smears should be made when the patient is afebrile. (C) Borreliae do not pass transovarially from one generation to the next in ticks. (D) The main reservoir for the Borrelia is deer. (E) Borrelia hermsii is resistant to penicillin and tetracycline.

A 23-year-old man presented with a maculopapular rash over much of his trunk but not in his mouth or on his palms. Because secondary syphilis was considered in the differential diagnosis, a RPR test was done, and the result was positive at a 1:2 dilution. However, the TP-PA test result was negative. Which of the following diseases can be ruled out? (A) Secondary syphilis (B) Atypical measles (C) Coxsackie virus infection (D) Acute HIV 1 infection (E) Allergic drug reaction

Which of the following animals is the source of Leptospira interrogans? (A) Cattle (B) Dogs (C) Mice (D) Rats (E) Swine (F) All of the above

A 27-year-old medical resident was admitted to the hospital because of sudden onset of fever to 39°C and headache. Two weeks previously, he had vacationed in rural Oregon, where he had frequently gone swimming in an irrigation canal that bordered land where cows were pastured. Blood tests done shortly after admission indicated renal function abnormality and elevated bilirubin and other liver function test results. Routine blood, urine, and CSF culture results were negative. Leptospirosis is suspected. Which of the following would be most likely to confirm this diagnosis? (A) Testing acute and convalescent phase sera using the RPR test (B) Culture of urine on human diploid fibroblast cells (C) Testing serum by dark-field examination for the presence of leptospires (D) Testing acute and convalescent phase sera for antileptospiral antibodies (E) Culture of CSF on blood and chocolate agar

A 47-year-old man presents with slowly progressive arthritis in his knees. He enjoys hiking in the coastal areas of Northern California, where the prevalence of Borrelia burgdorferi in the Ixodes ticks is known to be 1–3% (considered low). The patient is concerned about Lyme disease. He never noticed a tick on his body and did not see an expanding red rash. The result of an EIA for Lyme borreliosis is positive. What should be done now? (A) A biopsy specimen of the synovium of a knee joint should be examined for Borrelia burgdorferi. (B) The patient should be given an antibiotic to treat Lyme disease. (C) PCR on the patient’s plasma should be done to detect Borrelia burgdorferi. (D) A serum specimen should be submitted for immunoblot assay to detect antibodies reactive with Borrelia burgdorferi antigens.

Which of the following organisms principally infects the liver and kidneys? (A) Streptobacillus moniliformis (B) Leptospira interrogans (C) Staphylococcus aureus (D) Escherichia coli (E) Enterococcus faecalis (F) Treponema pallidum

Which of the following spirochetes are transmitted primarily by sexual contact? (A) Treponema pallidum subspecies pallidum (B) Treponema pallidum subspecies endemicum (C) Borrelia recurrentis (D) Borrelia burgdorferi (E) All of the above

Reverse sequence testing for the diagnosis of syphilis (A) Involves screening with a high-throughput EIA or CIA assay followed by confirmation using a nontreponemal test (B) May be associated with a high level of false-positive results (C) May be more sensitive than the traditional algorithm in detecting early disease (D) Is replacing the traditional algorithm in many laboratories (E) All of the above

All of the following statements regarding relapsing fever are correct except (A) Epidemic disease carries a higher mortality rate than endemic disease. (B) Endemic disease is North America is caused by B recurrentis. (C) The recurrent febrile episodes are caused by antigenic variation among the spirochetes. (D) Penicillin is the drug of choice. (E) Crushing a tick could transmit the spirochetes.

Nucleic acid amplification test results are sensitive methods for diagnosing neuroborreliosis. (A) True (B) False

Dark-field microscopy may be used to diagnose spirochetes in which of the following scenarios? (A) To detect spirochetes in the cerebrospinal fluid in a patient with tertiary syphilis (B) To detect spirochetes in a suspicious lesion in the oral cavity in a patient with secondary syphilis (C) To detect spirochetes in the urine of a patient with suspected leptospirosis (D) To detect spirochetes in the blood of a patient with a positive RPR result but no symptoms

Streptobacillus moniliformis is a cause of rat-bite fever. What other pathogen can also cause rat-bite fever? (A) Treponema pallidum subspecies pertenue (B) Leptospira interrogans (C) Borrelia recurrentis (D) Spirillum minor (E) Brachyspira aalborgi

Ureaplasma urealyticum is so named because (A) It thrives in the upper urinary tract. (B) It requires urea as a growth substrate. (C) It is a frequent cause of symptomatic urinary bladder infections in young women. (D) It causes chronic urinary tract infections in premature babies born to mothers with ureaplasmas as part of the genital flora.

An 18-year-old sexually active woman develops left lower quadrant pain and fever. On pelvic examination, she has tenderness in the left adnexa, and a mass suggestive of a uterine tube abscess is palpated. The patient is diagnosed with pelvic inflammatory disease. Which of the following bacteria is considered to be a common cause of pelvic inflammatory disease? (A) Bacillus cereus (B) Haemophilus influenzae (C) Neisseria subflava (D) Mycoplasma pneumoniae (E) Chlamydia trachomatis

Which of the following is important in the pathogenesis of mycoplasmal infections? (A) The peptidoglycan in the mycoplasmal cell wall (B) The presence of lacto-N-neotetraose with a terminal galactosamine as the host cell receptor (C) The structures and the interactive proteins that mediate adhesion to host cells (D) The absence of cilia on the surface of the host cells (E) Growth in an anatomic site where anaerobic organisms thrive

A 25-year-old woman is referred to the sexually transmitted diseases clinic because of contact with a male partner with gonorrhea. The woman has had 15 male sex partners since becoming sexually active. The likelihood that she also has genital Mycoplasma hominis infection is (A) 1% (B) 5% (C) 15% (D) 40% (E) 90%

A 25-year-old medical student has contact with a patient who has pneumonia with fever and cough. Four days later, the medical student develops fever and cough, and chest radiographs show consolidation of the right lower lobe. Routine bacterial sputum culture results are negative. Pneumonia caused by Mycoplasma pneumoniae is considered. All of the following are methods to confirm the clinical suspicion except (A) PCR amplification of M pneumoniae DNA in sputum (B) Culture of sputum for M pneumoniae (C) Gram stain of sputum smear (D) Culture of a lung aspirate for M pneumoniae (E) Enzyme immunoassay test of acute and convalescent sera

Each of the following is associated with genital tract infections except (A) Mycoplasma hominis (B) Neisseria gonorrhoeae (C) Mycoplasma pneumoniae (D) Chlamydia trachomatis (E) Mycoplasma genitalium

Mycoplasmas have all of the following characteristics except: (A) Possession of both DNA and RNA (B) Capability for cell-free growth (C) Susceptibility to penicillin G (D) Extracellular parasitism in vivo

Which type of test is most readily used to obtain laboratory confirmation of Mycoplasma pneumoniae infection? (A) Culture in broth containing serum, glucose, and a penicillin (to inhibit other flora) (B) PCR (C) Electron microscopy (D) EIA tests on acute and convalescent phase sera

A 13-year-old boy develops infection with Mycoplasma pneumoniae. What is the risk for infection in other members of his household? (A) None; it is sexually transmitted (B) 1–3% (C) 10–15% (D) 20–40% (E) 50–90%

A 19-year-old man develops cough and fever. A chest radiograph shows consolidation of the left lower lobe. A diagnosis of pneumonia is made. Which of the following bacteria is a frequent cause of community-acquired pneumonia? (A) Legionella pneumophila (B) Chlamydia pneumoniae (C) Streptococcus pneumoniae (D) Mycoplasma pneumoniae (E) All of the above

All of the following statements regarding mycoplasmas are correct except (A) They are susceptible to β-lactam agents. (B) They lack a cell wall. (C) They have an affinity for mammalian cell membranes. (D) They can be cultivated in cell-free media. (E) Some species are barely larger in size than viruses.

Initiation of infection by M pneumoniae begins with (A) Elaboration of a polysaccharide capsule that inhibits phagocytosis (B) Secretion of a potent exotoxin (C) Endocytosis by ciliated respiratory epithelial cells (D) Adherence to respiratory epithelial cells mediated by P1 adhesin (E) None of the above

Which of the following Mollicutes has the characteristic “fried egg” appearance on suitable agar media within 5–7 days of incubation? (A) Mycoplasma fermentans (B) Mycoplasma orale (C) Mycoplasma hominis (D) Mycoplasma pneumoniae (E) All of the above

A 53-year-old man with known prosthetic valve endocarditis presents with fever about 2 weeks after discontinuation of antibiotics. The infectious diseases physician in charge of the patient would like the laboratory to look for L forms. Which of the following statements best characterizes L forms? (A) They are cell wall–deficient forms that are unequivocally associated with infectious endocarditis. (B) They are cell wall–defective microbial forms that can replicate serially as nonrigid cells. (C) All L forms are stable and are different from the parent forms. (D) All L forms are derived from gram-positive bacteria. (E) L forms are genetically related to mycoplasmas.

In the case above, what is the best way to recover the L forms from blood cultures? (A) Place the blood into an isolator tube and subculture onto blood-containing media. (B) Add 15% gelatin to standard blood culture bottles. (C) L forms cannot be cultivated from human blood. (D) Add antibiotics that inhibit other microbes to standard blood culture media. (E) Place the blood into an isolator tube and subculture onto Mycoplasma media

Morulae (intracellular inclusions in leukocytes) are characteristic of which of the following diseases? (A) Malaria caused by Plasmodium falciparum infection but not Plasmodium malariae infection (B) Dengue (C) Babesia infection (D) Ehrlichiae infection (E) Loa loa

Which of the following statements about epidemic typhus (Rickettsia prowazekii disease) is most correct? (A) The disease occurs primarily in sub-Saharan Africa. (B) It is transmitted by ticks. (C) Mice are the reservoir. (D) Historically, the disease occurs in times of prosperity. (E) Recrudescence can occur many years after the initial infection.

The most useful drug to treat ehrlichiosis is (A) Doxycycline (B) Penicillin G (C) Trimethoprim–sulfamethoxazole (D) Gentamicin (E) Nitrofurantoin

A disease characterized by malaise, headache, rigors, and fever developed in members of several families living in an unheated war-damaged house in an Eastern European country. Erythematous 2–6 mm macular red rashes appeared on the peoples’ trunks and later on their extremities. Some of the people had coughs. One elderly person, although sick, was much less sick than other adults. The people huddled together to keep warm; body lice were common. Which of the following statements is most correct? (A) The disease that these people had is common in the Rocky Mountain states. (B) The elderly person may have had acute epidemic typhus many years ago and recrudescent typhus now. (C) Fleas from rodents in the house were spreading Rickettsia typhi. (D) The primary host of the body louse infecting the people is the rat. (E) Epidemic typhus can be prevented by a vaccine.

Which of the following statements about Ehrlichiae and ehrlichiosis is most correct? (A) Dogs and mice are reservoirs. (B) Mosquitoes are the vectors. (C) Ampicillin is the treatment of choice. (D) Culture is a good method to confirm the diagnosis. (E) Ehrlichiae are typically found in lymphocytes.

A group of urban teenagers visited a sheep ranch in a large Western state for a 2-week experience. While they were there, many of the pregnant ewes delivered lambs to the delight of the closely observing teenagers. About 10 days later, three of the teenagers developed flulike illnesses characterized by malaise, cough, and fever. One had an infiltrate on chest radiography, indicating pneumonia. The three teenagers had different doctors, but the physicians each drew a blood specimen and submitted it to the city health department for serologic testing. All three specimens were positive for Q fever. Public health investigators determined that all of the teenagers had been to the sheep ranch. When the investigators contacted the ranch, they were told that there was no Q fever there and that no one who lived at the ranch had been sick. The most likely explanation for the teenagers’ illnesses and the lack of illness at the ranch is (A) There was no Q fever at the ranch, and it was acquired elsewhere. (B) The people at the ranch had been previously immunized against Q fever. (C) The teenagers acquired Q fever at the ranch, and the people who lived there had all previously had Q fever and were now immune to it. (D) The teenagers had other illnesses, and the positive Q fever serology result was unrelated. (E) The public health laboratory had errors in the Q fever serologic tests.

A middle-aged sportsman, a resident of Oklahoma, took a hike through a rural wooded and brushy area near his home. The next morning, he noticed and removed a large (>1 cm) tick from his upper arm. About 1 week later, he experienced a gradual onset of fever and malaise. He now seeks medical attention because he is concerned about a possible infection transmitted by the tick. Which of the following diseases is most likely to be acquired from a tick? (A) Dengue (B) Rocky Mountain spotted fever (C) Typhus (D) Yellow fever (E) Malaria

Which of the following drugs should not be used to treat Rocky Mountain spotted fever (Rickettsia rickettsii infection)? (A) Trimethoprim–sulfamethoxazole (B) Chloramphenicol (C) Doxycycline

Which of the following should be used to prevent Rocky Mountain spotted fever (Rickettsia rickettsii infection)? (A) Attenuated Rickettsia rickettsii vaccine (B) Prophylactic doxycycline (C) Preventing tick bites by wearing protective clothing (D) Delousing with insecticide

One week after deer hunting in a wooded area, a 33-year-old man developed fever to 39°C with headache and malaise. Over the subsequent 24 hours, he developed nausea, vomiting, abdominal pain, and diarrhea. On day 4, he developed a rash, initially around the wrists and ankles, which then progressively evolved, involving the arms, trunk, palms, and soles. Initially the rash was macular, but it quickly evolved into maculopapules, some with central petechiae. Rocky Mountain spotted fever caused by Rickettsia rickettsii was diagnosed. Which of the following statements about Rocky Mountain spotted fever is correct? (A) The vectors of Rickettsia rickettsii are ticks of the genus Ixodes. (B) A rash consistently appears by day 4 of illness. (C) Rickettsia rickettsii forms inclusions in monocytes. (D) The patient’s antibody response may not occur until after the second week of illness. (E) The highest incidence of this disease is in the Rocky Mountain states.

The recommended treatment for Q-fever endocarditis is (A) Emergent surgery; antibiotics are not effective (B) Levofloxacin monotherapy for 6 weeks (C) 18 months of combination therapy with doxycycline and hydroxychloroquine (D) Penicillin and gentamicin combination therapy using IgG titers to determine duration

Coxiella burnetii can be transmitted by milk when animals such as goats and cows are infected. The presently recommended conditions of “high-temperature, short-time” pasteurization are adequate to destroy viable Coxiella organisms. (A) True (B) False

The histopathological hallmark of infection caused by Rickettsia rickettsiae is (A) Morulae within granulocytes (B) Morulae within monocytes (C) Granulomatous inflammation (D) Intracellular vacuoles (E) Perivascular lymphocytes

All of the following statements regarding Rickettsialpox are correct except (A) The cause of the disease is R akari. (B) Ticks of the genus Amblyomma are responsible for transmission. (C) The disease is mild. (D) Disease is more common in urban than rural areas.

Reasons why C burnetii could be a potential agent of bioterrorism include (A) It is acquired by the inhalation. (B) It is highly infectious. (C) It can be difficult to treat depending on the phase of infection. (D) Pneumonia may be severe. (E) All of the above.

Which of the following statements about chlamydial antigens is correct? (A) Chlamydiae have shared group or genus-specific antigens. (B) There is no cross-reaction between Chlamydia trachomatis and Chlamydophila pneumoniae antigens. (C) All five serovars of Chlamydophila pneumoniae cross-react with Chlamydia psittaci. (D) One serovar of Chlamydia trachomatis causes eye infections, and the second serovar causes genital infections.

The following are part of the control of Chlamydia psittaci and psittacosis in birds except (A) Quarantine of psittacine birds imported into the United States (B) Only allowing sale of psittacine birds hatched in the United States (C) Testing of birds for C psittaci infection (D) Controlling the shipment of psittacine birds (E) Putting tetracycline in the feed of psittacine birds

All of the following statements about perinatal Chlamydia trachomatis infections are correct except (A) Between 15% and 40% of infants born to infected women develop inclusion conjunctivitis. (B) Between 10% and 20% of infants born to infected women develop infant pneumonia. (C) The incubation period for C trachomatis inclusion conjunctivitis is 1–2 days. (D) The incubation period for infant pneumonia is typically 2–12 weeks. (E) Ocular prophylaxis with erythromycin or tetracycline for neonatal Neisseria gonorrhoeae infection is generally not effective against neonatal C trachomatis infection. (F) Infant pneumonia caused by C trachomatis often presents with a staccato cough.

An adolescent girl came to the clinic because of a new and unusual vaginal discharge. She had recently become sexually active and had two new partners during the previous month. On pelvic examination, a purulent discharge was seen at the opening of her endocervical canal. Which of the following statements about this patient is most correct? (A) A serologic test for syphilis is not indicated because her symptoms are not those of syphilis. (B) A Gram stain of her endocervical specimen would show Chlamydia trachomatis inside polymorphonuclear cells. (C) The differential diagnosis includes infection with Neisseria gonorrhoeae, Chlamydia trachomatis, or both. (D) The endocervical specimen should be analyzed for herpes simplex. (E) Initial treatment is with ampicillin.

The following statements about trachoma are correct except (A) It follows chronic or recurrent eye infection with Chlamydia trachomatis. (B) Millions of people worldwide have trachoma. (C) Trachoma is readily prevented by a chlamydial vaccine. (D) Progression of trachoma can be slowed by intermittent treatment with azithromycin. (E) Trachoma involves scarring of the conjunctiva, eyelid deformities, and eyelash injury to the cornea.

Elimination of blinding trachoma involves all of the following except (A) Periodic administration of azithromycin (B) Face washing and hygiene (C) Periodic culture screening of conjunctiva swab specimens for Chlamydia trachomatis (D) Environment improvements to sewage systems to decrease the number of flies (E) Surgery on deformed eyelids

Which one of the following statements about Chlamydophila pneumoniae is most correct? (A) Transmission from person to person is by the airborne route. (B) It makes glycogen-rich inclusions that stain with iodine. (C) There are multiple serovars, including three that cause a systemic illness. (D) They are resistant to macrolides. (E) The reservoir is house cats.

The serovars of Chlamydia trachomatis generally can be divided into groups representing their clinical infections and anatomic site infected. Which of the following statements about the Chlamydia trachomatis serovars is most correct? (A) There is no immunologic cross-reaction between Chlamydia trachomatis serovars A, B, Ba, and D and the Chlamydophila pneumoniae serovar. (B) Serovars L1, L2, and L3 are associated with lymphogranuloma venereum. (C) The same Chlamydia trachomatis serovars are associated with blinding trachoma and sexually transmitted infections. (D) The antibody titer rise seen beginning about around 6–8 years follows infections with Chlamydia trachomatis serovars D–K.

In the United States, it has long been known that the positive seroprevalence for Chlamydia trachomatis infection increases greatly during the primary school years (ages 6–10 years). A likely reason for this is (A) Frequent adenovirus infections (B) Increased incidence of infections with C trachomatis (C) Cross-reactive antibodies with M protein of group A streptococci (Streptococcus pyogenes) (D) Children often have psittacosis (E) Frequent infections with Chlamydophila pneumoniae

All of the following statements about lymphogranuloma venereum (LGV) are correct except (A) Chronic LGV proctitis can lead to rectal strictures and fistula formation. (B) The disease is more common in northern latitudes. (C) There may be marked systemic symptoms, including fever, nausea, vomiting, headache, and meningismus. (D) Chronic inflammation with LGV can lead to lymphatic obstruction. (E) Inguinal lymph nodes may become enlarged and matted, draining pus through the skin. (F) A few days or weeks after exposure, the disease manifests itself as a genital papule or vesicle.

Which of the following methods are considered the diagnostic tests of choice for urogenital infections caused by Chlamydia trachomatis? (A) Serology using complement fixation (B) Cell culture using cycloheximide containing McCoy cells (C) Direct fluorescent antibody testing on urethral and cervical specimens (D) Nucleic acid amplification methods (E) Enzyme immunoassays performed on genital tract specimens

Nucleic acid amplification tests that are currently available in the United States for diagnosing chlamydial infections are approved for testing all of the following specimens except (A) Self-collected vaginal swabs in women (B) First void urine samples obtained from men (C) Rectal swabs obtained from children 12 years of age or younger (D) Urethral swab samples obtained from adult men (E) Cervical swab samples obtained from adolescent girls

Chlamydia pneumoniae pneumonia most resembles infection caused which of the following organisms? (A) Streptococcus pneumoniae (B) Mycoplasma pneumoniae (C) Haemophilus influenzae (D) Chlamydia trachomatis (E) Rhinovirus

Inclusion conjunctivitis of the newborn (A) Is a mucopurulent conjunctivitis that occurs 7–12 days after delivery (B) Is caused by C psittaci (C) Is a result of exposure to pet birds in the home (D) Is treated with systemic penicillin because it may progress to pneumonia (E) None of the above

The diagnostic method of choice for C trachomatis pneumonia in the newborn is (A) A nucleic acid amplification test that the targets the ompA gene (B) Culture of respiratory secretions in McCoy cells or other cell lines (C) Enzyme immunoassay testing of respiratory secretions (D) IgG antibodies detected by complement fixation

The antimicrobial agent whose structure is shown below is considered the drug of choice to treat infections caused by which one of the following microorganisms? (A) Bacteroides fragilis (B) Pseudomonas aeruginosa (C) Herpes simplex virus (D) Streptococcus pyogenes (group A streptococci) (E) Mycobacterium tuberculosis

Resistance of Staphylococcus aureus to the drug shown in Question 1 is caused by (A) The action of acetyltransferase (B) The action of β-lactamase (C) Substitution of the d-Ala-d-Ala dipeptide with the d-Ala d-Lac dipeptide in the cell wall peptidoglycan (D) Decreased permeability of the bacterial cell wall to the drug (E) Staphylococcus aureus being an intracellular pathogen

Streptococcus pneumoniae resistance to the drug shown in Question 1 is caused by (A) The action of acetyltransferase (B) The action of β-lactamase (C) Substitution of the d-Ala-d-Ala dipeptide with d-Ala d-Lac dipeptide in the cell wall peptidoglycan (D) Decreased permeability of the bacterial cell wall (E) Genetically modified binding proteins in the bacterial cell wall

All of the following statements about antimicrobial resistance of enterococci are correct except (A) Enterococci are resistant to sulfamethoxazole–trimethoprim in vivo. (B) Cephalosporins are not active against enterococci. (C) Resistance to the streptogramins (quinupristin–dalfopristin) has emerged. (D) Vancomycin-resistant enterococci are rare in Europe and the United States. (E) Vancomycin-resistant enterococci once consistently clonal are now heterogeneous.

A 20-year-old Asian woman, a recent immigrant to the United States, develops fever and a cough productive of blood-streaked sputum. She has lost 6 kg of body weight in the past 6 weeks. Her chest radiograph shows bilateral upper lobe infiltrates with cavities. Given the history and chest radiography findings, which of the following drug regimens would be the best appropriate initial therapy while awaiting culture results? (A) Isoniazid, rifampin, pyrazinamide, and ethambutol (B) Penicillin G and rifampin (C) Cefotaxime, clindamycin, and trimethoprim–sulfamethoxazole (D) Ampicillin–sulbactam (E) Vancomycin, gentamicin, and clindamycin

Aminoglycoside antibiotics typically cause which of the following adverse events? (A) They cause aplastic anemia. (B) They cause nonspecific stimulation of B cells. (C) They cause ototoxicity and nephrotoxicity. (D) They cause photosensitivity.

Which one of the following groups of antimicrobial agents acts on microorganisms by inhibiting protein synthesis? (A) Fluoroquinolones (B) Aminoglycosides (C) Penicillins (D) Glycopeptides (eg, vancomycin) (E) Polymyxins

There are many bacterial–antimicrobial resistance combinations. Which one of the following is of major international concern? (A) Sulfonamide resistance in Neisseria meningitidis (B) Penicillin G resistance in Neisseria gonorrhoeae (C) Ampicillin resistance in Haemophilus influenzae (D) Erythromycin resistance in Streptococcus pyogenes (group A streptococci) (E) Vancomycin resistance in Staphylococcus aureus

Which of the following factors is not generally considered when selecting initial antimicrobial therapy for an infection? (A) Age of the patient (B) Anatomic site of the infection (eg, meningitis or urinary tract infection) (C) Whether or not the patient is immunocompromised (D) Whether or not the patient has implanted devices in place (eg, artificial hip joint, artificial heart valve, urinary catheter) (E) Waiting for culture and susceptibility test results

All of the following agents have good activity against gram-positive organisms except (A) Daptomycin (B) Vancomycin (C) Aztreonam (D) Quinupristin–dalfopristin (E) Tigecycline

Tigecycline, a new glycylcycline antibiotic with good activity against a variety of pathogens, is best used for treatment of which of the following infections? (A) Meningitis (B) Intra-abdominal infections caused by mixed aerobic and anaerobic bacteria (C) Neonatal sepsis (D) Urethritis caused by Chlamydia trachomatis (E) As monotherapy for bacteremia caused by Acinetobacter baumannii

Which of the following carbapenem antibiotics has no activity against Pseudomonas aeruginosa? (A) Imipenem (B) Meropenem (C) Doripenem (D) Ertapenem

Which of the following agents would not be expected to demonstrate postantibiotic effect against gram-negative bacilli? (A) Imipenem (B) Ciprofloxacin (C) Gentamicin (D) Ampicillin

All of the following are common mechanisms of resistance to the penicillins except (A) Production of β-lactamases (B) Alterations in target receptors (PBPs) (C) Inability to activate autolytic enzymes (D) Failure to synthesize peptidoglycans (E) Methylation of ribosomal RNA

The drug of first choice for the treatment of serious anaerobic infections caused by Bacteroides fragilis is (A) Clindamycin (B) Ampicillin (C) Cefoxitin (D) Metronidazole (E) Amoxicillin–clavulanate

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