Elsevier MICRO Flashcards by Karl Dashley Atinen

Spores are found in select groups of bacteria. Which of the following statements describes the major advantage to the bacteria that possess these structures?

a. Spores are resistant to heat, cold, drying, most chemicals, and boiling
b. Spores allow an organism to better control its local environment
c. Spores allow bacteria to attach or adhere to host tissues
d. Organisms with spores have a more efficient exchange of genetic material

a. Spores are resistant to heat, cold, drying, most chemicals, and boiling

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Choose the binomial name that is correctly written.

a. Staphylococcus Aureus
b. Staphylococcus species aureus
c. Staphylococcus aureus
d. Staphylococcus aureus

c. Staphylococcus aureus

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Fermentation end-products are often used to aid in the identification of bacteria. Fermentation results in which of the following?

a. Conversion of glucose to pyruvate
b. Lactic acid, mixed acids, alcohols, CO2 production
c. CO2 and water
d. Specific teichoic acids

b. Lactic acid, mixed acids, alcohols, CO2 production

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The exchange of cellular DNA between two living bacterial cells that involves an intercellular bridge is which of the following processes?

a. Transformation
b. Transduction
c. Plasmidization
d. Conjugation

d. Conjugation

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Transduction is defined as which of the following?

a. The change of the bacterial genotypes through the exchange of DNA from one cell to another
b. An internal change in the original nucleotide sequence of a gene or genes within an organism’s genome
c. The process by which genetic elements such as plasmids and transposons excise from one genomic location and insert into another
d. A mechanism that is mediated by viruses, by which DNA from two bacteria may come together in one
cell, thus allowing for recombination

d. A mechanism that is mediated by viruses, by which DNA from two bacteria may come together in one cell, thus allowing for recombination

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A mordant that is applied after the primary stain to chemically bond the alkaline dye to the bacterial cell
wall is which of the following?

a. Safranin
b. Crystal violet
c. Gram’s iodine
d. Gram’s decolorizer

c. Gram’s iodine

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Which of the following bacteria should be considered important pathogens when reading gram-stained
smears of soft tissue abscess?

a. Streptococcus pneumoniae
b. Neisseria gonorrhoeae
c. Pseudomonas aeruginosa
d. Staphylococcus aureus

d. Staphylococcus aureus

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The most appropriate interpretation of a gram stained smear of a sputum specimen would be which of the following? (gram-stained smear, 400x.)

a. Few epithelial cells, many PMNs
b. Inadequate specimen, do not culture for anaerobes
c. Many cells, many gram-positive cocci in pairs and chains
d. More than 25 epithelial cells, probable oral contamination, suggest recollect

d. More than 25 epithelial cells, probable oral contamination, suggest recollect

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85% N2, 10% H2, 5% CO2 is the environmental condition that best suits which type of organism?

a. Aerobes
b. Anaerobes
c. Capnophiles
d. Microaerophiles

b. Anaerobes

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Which medium can be described as containing bile salts and dyes(bromothymol blue and acid fuchsin) to selectively slow the growth of most nonpathogenic gram negative bacilli found in the gastrointestinal tract and allow Salmonella spp. and Shigella spp. to grow?

a. Thayer-Martin
b. MacConkey
c. PEA (phenylethyl alcohol)
d. Hektoen

d. Hektoen

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Choose the group of bacteria that is described as catalase-positive, gram-positive cocci that grow facultatively anaerobic and that form grapelike clusters.

a. Neisseria spp.
b. Rothia (Stomatococcus) spp.
c. Staphylococcus spp.
d. Micrococcus spp.

c. Staphylococcus spp.

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The slide coagulase test is a rapid screening test for the production of which of the following?

a. Clumping factor
b. Free coagulase
c. Extracellular coagulase
d. Catalase

a. Clumping factor

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The first identification test performed on a clinical isolate of gram-positive, catalase-positive cocci should be which of the following?

a. Penicillin test
b. Gram stain
c. Oxidase test
d. Coagulase test

d. Coagulase test

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The Staphylococcus sp. that is more likely to cause uncomplicated urinary tract infections in non hospitalized hosts, especially sexually active
young women, is which of the following?

a. Staphylococcus saprophyticus
b. Staphylococcus aureus
c. Staphylococcus epidermidis
d. Staphylococcus intermedius

a. Staphylococcus saprophyticus

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The toxic shock syndrome toxin-1 is an important virulence factor in staphylococcal disease. This toxin is
classified into which of the following groups of toxins?

a. Cytolytic toxin
b. Leukocidin
c. Phospholipase
d. Enterotoxin

d. Enterotoxin

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Mannitol salt agar is selective and differential for which group of organisms?

a. Staphylococcus spp.
b. Enterococcus spp.
c. Gram-positive cocci
d. Streptococcus spp.

a. Staphylococcus spp.

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Within 5 hours of returning home from lunch at your most favorite fast food restaurant you feel very sick and are vomiting. Which of the following is the most likely causative organism?

a. Staphylococcus aureus
b. Vibrio parahaemolyticus
c. Shigella sonnei
d. Escherichia coli

a. Staphylococcus aureus

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The bacterial species that can be described as susceptible to bile and optochin, a-hemolytic, a major cause
of bacterial meningitis, and often carrying an antiphagocytic capsule is which of the following?

a. Enterococcus faecalis
b. Streptococcus pneumoniae
c. Streptococcus pyogenes
d. Streptococcus agalactiae

b. Streptococcus pneumoniae

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The bacterial species that can be described as susceptible to penicillin and bacitracin, b-hemolytic, a major
cause of bacterial pharyngitis, and often carrying an antiphagocytic M protein is which of the following?

a. Enterococcus faecalis
b. Streptococcus pyogenes
c. Streptococcus agalactiae
d. Viridans streptococci

b. Streptococcus pyogenes

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The bacterial species that can be described as able to hydrolyze hippurate, b-hemolytic, a major cause of neonatal meningitis and sepsis, and producer of the CAMP factor is which of the following?

a. Streptococcus pneumoniae
b. Streptococcus pyogenes
c. Streptococcus agalactiae
d. Viridans streptococci

c. Streptococcus agalactiae

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The rapid antigen detection methods for throat swabs used for screening patients for streptococcal pharyngitis can be best described by which of the following statements?

a. They can be useful in quickly identifying most cases of streptococcal pharyngitis
b. They are a quick way to rule out streptococcal pharyngitis and avoid giving antibiotics when not needed
c. They are always very sensitive and specific for streptococcal pharyngitis
d. They are a quick and accurate way to diagnose bacterial and viral pharyngitis

a. They can be useful in quickly identifying most cases of streptococcal pharyngitis

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The hemolysis of this Streptococcus spp. would best be described as which of the following?

a. b-Hemolysis
b. g-Hemolysis
c. a-Hemolysis
d. k-Hemolysis

c. a-Hemolysis

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Enterococcus spp. can be differentiated from most Streptococcus spp. by which of the following tests?

a. Growth in presence of 6.5% salt
b. Production of catalase
c. Production of coagulase
d. Growth on PEA medium

a. Growth in presence of 6.5% salt

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A pure culture of a b-hemolytic Streptococcus sp. recovered from a leg ulcer gave the following reactions:
CAMP test = Negative
Hippurate hydrolysis = Negative
Bile esculin slant = No growth
6.5% Salt = No growth
PYR = Negative
Bacitracin = Resistant
Optochin = Resistant
SXT = Sensitive
Which of the following is the most likely identification of this organism?

a. Streptococcus pyogenes
b. Streptococcus agalactiae
c. Enterococcus faecalis
d. Streptococcus sp., not groups A, B, or D

d. Streptococcus sp., not groups A, B, or D

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The ability to grow well at refrigerator temperatures is a characteristic of which of the following organisms? a. Mycobacterium gordonae b. Listeria monocytogenes c. Erysipelothrix d. Bacillus cereus

b. Listeria monocytogenes

A catalase-positive, gram-positive bacillus that is not acid-fast, does not branch, and does not form spores could possibly belong to which group of bacteria? a. Corynebacterium b. Bacillus c. Nocardia d. Mycobacterium

a. Corynebacterium

A throat culture was taken from a 6-year-old boy with a gray pseudomembrane covering his oropharynx. A catalase-positive organism was isolated on cysteine-tellurite medium and subcultured to Tinsdale medium, where it grew as black colonies with brown halos. A Gram stain was performed on these colonies. Which of the following cellular morphologies was most likely seen? a. Gram-positive branching bacilli b. Gram-positive cocci in short chains c. Gram-positive bacilli in irregular clublike shape d. Gram-positive cocci in grapelike clusters

c. Gram-positive bacilli in irregular clublike shape

A blood culture is positive for gram-positive bacilli that gave the following growth characteristics and biochemical reactions: MacConkey agar: No growth Catalase: Positive H2S on TSI: negative Growth of blood agar, nonhemolytic Nonmotile No spores These reactions are consistent with which of the following organisms? a. Listeria spp. b. Group B b Streptococcus c. Erysipelothrix spp. d. Corynebacterium spp.

d. Corynebacterium spp.

A skin lesion was opened and drained in surgery. The culture was positive for a gram-positive bacillus, which gave the following growth characteristics and biochemical reactions: MacConkey agar: No growth Catalase: Negative H2S on TSI: Positive Growth of blood agar, nonhemolytic Nonmotile No spores These reactions are consistent with which of the following organisms? a. Listeria spp. b. Group B b Streptococcus c. Erysipelothrix spp. d. Corynebacterium spp.

c. Erysipelothrix spp.

Which of the following sets of tests provide the best differentiation of Erysipelothrix from Listeria monocytogenes? a. Gram-stained smear, oxidase, and optochin b. Gram-stained smear, catalase, and motility c. CAMP test, hydrogen sulfide production, esculin hydrolysis d. Reverse CAMP, gram-stained smear, b-hemolysis

c. CAMP test, hydrogen sulfide production, esculin hydrolysis

Neonatal meningitis is an uncommon but significant disease. Two important causes of this disease may be somewhat difficult to differentiate on preliminary observation. Which of the following sets of tests provide the best differentiation of Streptococcus agalactiae from Listeria monocytogenes? a. Gram-stained smear, oxidase, and optochin b. Gram-stained smear, catalase, and motility c. CAMP test, hydrogen sulfide production, b-hemolysis d. Reverse CAMP, gram-stained smear, b-hemolysis

b. Gram-stained smear, catalase, and motility

Which of the following tests is important as a part of the genus identification or as part of a preliminary identification but is not used as a confirmatory identification of Bacillus anthracis? a. Demonstration of a capsule b. Demonstration of spore formation c. Positive PCR test d. Lysis of the strain by specific bacteriophages

b. Demonstration of spore formation

Bacillus anthracis and Bacillus cereus can be differentiated in the laboratory by a variety of different test results. Which of the following sets of tests best differentiate these two species? a. Catalase and glucose fermentation b. Motility and lecithinase production c. Oxidase and b-hemolysis on 5% sheep blood agar d. Motility and b-hemolysis on 5% sheep blood agar

d. Motility and b-hemolysis on 5% sheep blood agar

Which of the following specimens would be best for identifying Bacillus cereus as the cause of an outbreak of food poisoning? a. Blood b. Rectal swabs c. Stool samples d. Food

d. Food

A first morning sputum sample is received for acid fast culture. The specimen is centrifuged, and the sediment is inoculated on two Lowenstein-Jensen slants that are incubated at 35C with 5% to 10% CO2. After 1 week, the slants show abundant growth over the entire surface. Stains reveal gram-negative bacilli. Which of the following should be done to avoid this problem? a. Use a medium specifically designed for the growth of AFB b. Dilute out the sediment before inoculation with saline c. Decontaminate the specimen with NALC– sodium hydroxide mixture d. Incubate the tubes at room temperature to retard bacterial growth

c. Decontaminate the specimen with NALC– sodium hydroxide mixture

A patient recently arrived in the United States from Africa presents with a long-standing cutaneous lesion, which is cultured for bacteria, fungi, and AFB. An AFB smear is made and is reported as positive for AFB. After 8 weeks of culture on both nonselective and selective AFB media, no colonies appear. Which of the following organisms should be suspected? a. M. kansasii b. M. tuberculosis c. M. leprae d. M. avium-intracellulare complex

c. M. leprae

The mycobacterial species that occur in humans and belong to the M. tuberculosis complex include which of the following? a. M. tuberculosis, nontuberculous Mycobacteria, M. bovis, and M. africanum b. M. tuberculosis, M. gordonae, M. bovis BCG, and M. africanum c. M. tuberculosis, M. bovis, M. avium, and M. intracellulare d. M. tuberculosis, M. bovis, M. bovis BCG, and M. africanum

d. M. tuberculosis, M. bovis, M. bovis BCG, and M. africanum

The Runyon system of classification is based on which of the following? a. Colony and microscopic morphology b. Biochemical characteristics c. Growth rate and colonial pigmentation d. All of the above are correct

c. Growth rate and colonial pigmentation

In identification of mycobacterial isolates, the Tween 80 test involves which of the following? a. An enzyme that is able to produce Tween 80 from certain ingredients found in the medium b. Lipase that is able to hydrolyze polyoxyethylene sorbitan monooleate into oleic acid and polyoxyethylated sorbitol c. The metabolism of niacin to nicotinic acid by enzymatic action d. Testing the isolate for susceptibility to Tween 80

b. Lipase that is able to hydrolyze polyoxyethylene

The gram-negative bacillus that can be described as oxidase-negative, nitrate-positive, indole-negative, citrate-positive, methyl red–positive, urease negative, and H2S-positive is most likely which of the following? a. Klebsiella pneumoniae b. Salmonella enteritidis c. Escherichia coli d. Shigella sonnei

b. Salmonella enteritidis

The swarming gram-negative bacillus that can be described as oxidase-negative, nitrate-positive, indole-negative, and H2S-positive is mostly likely which of the following? a. Proteus aerogenes b. Proteus vulgaris c. Proteus mirabilis d. Escherichia coli

c. Proteus mirabilis

Profuse watery diarrhea (“rice water stools”), leading to dramatic fluid loss, severe dehydration, and hypotension that frequently leads to death, is the hallmark of which toxin activity? a. Cholera toxin b. Enteric endotoxin c. Shiga toxin d. Toxin A

a. Cholera toxin

The selective medium thiosulfate citrate bile salts sucrose (TCBS) agar is especially formulated for isolating which pathogen from stool cultures? a. Vibrio spp. b. Salmonella spp. c. Shigella spp. d. Plesiomonas spp.

a. Vibrio spp.

The majority of human infections with Campylobacter spp. are caused by which of the following? a. Direct contact with carriers of the bacterium b. Contamination of food, milk, or water with animal feces c. Multiplication of the organism in food products d. Direct contact with persons infected with the bacterium

b. Contamination of food, milk, or water with animal feces

In the test for urease production, the presence of the enzyme hydrolyzes urea to which of the following? a. Ammonia and CO2 b. Putrescine c. Amines and CO2 d. Amines and water

a. Ammonia and CO2

The bacterial isolate on XLD agar shown in the image was isolated from a routine stool culture. Which of the following genera and species is the most likely identification for this organism? a. Klebsiella pneumoniae b. Salmonella enteritidis c. Shigella sonnei d. Serratia marcescens

b. Salmonella enteritidis

The bacterial isolate shown below on CIN agar was isolated from a routine stool culture. Which of the following genera and species is the most likely identification for this organism? a. Shigella flexneri b. Salmonella enteritidis c. Yersinia enterocolitica d. Escherichia coli

c. Yersinia enterocolitica

Decarboxylation of the amino acids lysine, ornithine, and arginine results in the formation of which of the following products? a. Ammonia b. Urea c. CO2 d. Amines

d. Amines

An organism was inoculated into a TSI tube and gave the following reactions: Alkaline slant Acid butt H2S: Not produced Gas: Not produced The organism is most likely which of the following? a. Klebsiella sp. b. Shigella sp. c. Salmonella sp. d. Escherichia coli

b. Shigella sp.

The best specimen for the isolation of Bordetella pertussis is which of the following? a. Throat swabs b. Sputum c. Nasopharyngeal aspirates d. Anterior nose swab

c. Nasopharyngeal aspirates

Organisms belonging to the genus Brucella are best described by which of the following statements? a. Gram-positive diplococci b. Gram-positive diphtheroid bacilli c. Gram-negative coccobacilli d. Gram-negative bacilli

c. Gram-negative coccobacilli

Serum samples collected on a patient with pneumonia demonstrate a rising antibody titer to Legionella. A bronchoalveolar lavage sample was collected and revealed a positive DFA test for Legionella, but no organisms were recovered from this specimen when it was cultured on the appropriate medium and incubated for 2 days at 35C in CO2. Which of the following is the best explanation? a. Culture was not incubated long enough b. Antibody titer c. Specimen was incubated at the wrong temperature d. Positive DFA test result is a false positive

a. Culture was not incubated long enough

Of the following media, which provides the NAD necessary for the growth of Haemophilus spp.? a. 5% sheep blood agar b. Brain heart infusion agar c. Chocolate agar d. Nutrient agar

c. Chocolate agar

Performing the factor requirement test for Haemophilus involves which of the following processes? a. Inoculation of unsupplemented media with a light suspension of the organism and placement of factors X and V disks on the agar surface b. Inoculation of liquid media, unsupplemented and supplemented with factors X and V c. Detecting the presence of enzymes that convert aaminolevulinic acid (ALA) into porphyrins d. Growth of the organism in the presence of bacterial species that produce X and V factors as metabolic by-products

a. Inoculation of unsupplemented media with a light suspension of the organism and placement of factors X and V disks on the agar surface

Of the asaccharolytic, oxidase-positive bacilli that do not grow on MacConkey agar, which one is among the HACEK group of bacteria known to cause subacute bacterial endocarditis? a. Eikenella corrodens b. Weeksella virosa c. Pseudomonas maltophilia d. Sphingomonas paucimobilis

a. Eikenella corrodens

Which of the following statements best completes the following thought: Presumptive identification of an oxidase-positive, gram-negative diplococcus on Thayer-Martin medium from genital sites of a 6- year-old female as Neisseria gonorrhoeae? a. Provides the physician with quick and reliable results at minimal cost b. May sometimes be incorrect, and a repeat culture should be collected c. May sometimes be incorrect and should not be reported until confirmed d. Should be done only when venereal disease is suspected

c. May sometimes be incorrect and should not be reported until confirmed

The bacterial species that can be described as oxidase positive, glucose-positive, maltose-positive, sucrose negative, lactose-negative, and a major cause of bacterial meningitis is most likely which of the following? a. Neisseria meningitidis b. Neisseria gonorrhoeae c. Streptococcus pneumoniae d. Viridans group Streptococcus

a. Neisseria meningitidis

The bacterial species that can be described as oxidase positive, glucose-positive, maltose-negative, sucrose negative, lactose-negative, and a major cause of venereal disease is most likely which of the following? a. Neisseria meningitidis b. Neisseria gonorrhoeae c. Streptococcus pyogenes d. Viridans group Streptococcus

b. Neisseria gonorrhoeae

Organisms belonging to the genus Neisseria are described as which of the following? a. Gram-positive diplococci b. Gram-negative diplococci c. Gram-negative coccobacilli d. Gram-negative bacilli

b. Gram-negative diplococci

The following were observed when the Hugh-Leifson oxidative-fermentative test was performed on a bacterial isolate. Which of the options below best describes the organism’s reaction? a. Oxidizer b. Nonoxidizer c. Fermenter d. Nonviable

a. Oxidizer

The oxidase test is a critical test when attempting to identify nonfermenting gram-negative bacilli. This test is designed to determine the presence of which of the following? a. b-Galactosidase b. Cytochrome oxidase c. Glucose oxidizing enzymes d. Oxygen

b. Cytochrome oxidase

The blood culture of a patient with a central venous catheter yielded a gram-negative bacillus growing on MacConkey agar with the following reactions: Oxidase = Negative Motility = Positive Glucose oxidative fermentative open = Positive (weak) Maltose oxidative-fermentative open = Positive (strong) Catalase = Positive Esculin hydrolysis = Positive Which of the following is the most likely identification of this organism? a. Burkholderia cepacia b. Pseudomonas aeruginosa c. Acinetobacter baumannii d. Stenotrophomonas maltophilia

d. Stenotrophomonas maltophilia

Which organism is associated with the disease Melioidosis? a. Burkholderia ralstonia b. Burkholderia pseudomallei c. Burkholderia mallei d. Burkholderia cepacia

b. Burkholderia pseudomallei

Differentiation of Stenotrophomonas maltophilia and Burkholderia cepacia is best accomplished by which of the following tests? a. Oxidase test b. Maltose and glucose medium c. Tyrosine-enriched heart infusion agar d. Growth at 42 C

a. Oxidase test

The respiratory culture of a patient with cystic fibrosis yielded a gram-negative bacillus with the following reactions: Oxidase = Positive Motility = Positive Glucose oxidative-fermentative open = Positive Gelatin hydrolysis = Positive Soluble green pigment on TSA slant Arginine dihydrolase = Positive Growth at 42C = positive Which of the following is the most likely identification of this organism? a. Burkholderia cepacia b. Pseudomonas aeruginosa c. Acinetobacter baumannii d. Stenotrophomonas xylosoxidans

b. Pseudomonas aeruginosa

Which test group best differentiates Acinetobacter baumannii from Pseudomonas aeruginosa? a. Oxidase, motility, nitrate reduction b. Growth on MacConkey agar, catalase, nitrate reduction c. Growth on blood agar, oxidase, catalase d. TSI, urea, motility

a. Oxidase, motility, nitrate reduction

Which of the following sets of results represent the most common reactions for Moraxella catarrhalis when tested in CTA sugar tubes? a. Glucose: Negative; Maltose: Negative; Lactose: Negative; Sucrose: Negative b. Glucose: Positive; Maltose: Negative; Lactose: Negative; Sucrose: Negative c. Glucose: Positive; Maltose: Positive; Lactose: Negative; Sucrose: Negative d. Glucose: Positive; Maltose: Negative; Lactose: Positive; Sucrose: Negative

a. Glucose: Negative; Maltose: Negative; Lactose: Negative; Sucrose: Negative

A soluble, bright green pigment can be produced by Pseudomonas aeruginosa. This pigment is known as which of the following? a. Pyoverdin b. Pyocyanin c. Pyorubin d. Pyophena

b. Pyocyanin

A small portion of a colony of a gram-negative bacilli was smeared onto a filter paper test system. One percent tetramethyl-p-phenylenediamine dihydrochloride was added. At 10 seconds, a dark purple color developed where the colony was added to the paper. Which of the following statements best describes the test results? a. Positive indole test b. Positive oxidase test c. Positive urea test d. Positive esculin test

b. Positive oxidase test

Characteristics of Mycoplasma and Ureaplasma include which of the following? a. They exhibit the presence of a thin gram-positive– like cell wall with no cell membrane b. They demonstrate rapid growth on MacConkey agar, slow growth on basic nutrient agar c. The have only a cell membrane with no cell wall d. They exhibit rapid growth on MacConkey medium and routine blood agar plates

c. The have only a cell membrane with no cell wall

Which of the following is a cause of nongonococcal urethritis? a. Mycoplasma hominis b. Mycoplasma pneumoniae c. Ureaplasma urealyticum d. Mycoplasma orale

c. Ureaplasma urealyticum

Which of the following is the most sensitive method for the diagnosis of Chlamydia trachomatis? a. Cytology b. Culture c. Nucleic acid amplification d. Serologic testing

c. Nucleic acid amplification

An 8-year-old boy from Oklahoma presents with a 3-day history of fever, headache, and muscle aches. A rash first noted this morning on his ankles and wrists has now spread to include his trunk. The medical team has identified a list of possible organisms. Which of the following is the most likely cause of this infection? a. Q Fever b. Ehrlichiosis c. Rocky Mountain spotted fever d. Cat scratch disease

c. Rocky Mountain spotted fever

Which of the following is a stage of venereal syphilis that is characterized by the appearance of a chancre? a. Primary syphilis b. Secondary syphilis c. Late syphilis d. Tertiary syphilis

a. Primary syphilis

Which of the following is a nontreponemal serologic test in which soluble antigen particles are coalesced to form larger particles that are visible as clumps when they are aggregated by antibody? a. Nontreponemal flocculation (NTF) b. Fluorescent treponemal antibody absorption (FTA-ABS) test c. Venereal Disease Research Laboratory (VDRL) test d. T. pallidum particle agglutination (TP-PA) test

c. Venereal Disease Research Laboratory (VDRL) test

A patient in a rural area of Massachusetts had a 5-cm red rash with an expanding margin on his back. The lesion was obvious for approximately a month and then resolved. Several weeks later, the patient experienced episodes of partial facial paralysis and painful joints. Which of the following is the most likely infectious agent in this case? a. Borrelia hermsii b. Borrelia burgdorferi c. Leptospira interrogans d. Spirillum minor

b. Borrelia burgdorferi

A 16-year-old, sexually active patient comes to his physician’s office because of a circular, 1-cm lesion in the groin area which is ulcerated but not painful. A rapid plasma reagin test is performed and is reactive with a titer of 1:16. Culture and gram-stain smear results from an exudate of the lesion are negative. Which of the following is the most likely cause of this lesion? a. Chlamydia trachomatis b. Neisseria gonorrhoeae c. Treponema pallidum d. Haemophilus ducreyi

c. Treponema pallidum

The gram-stained smear shows an organism isolated from a blood culture after bowel surgery. Under anaerobic incubation conditions, it grew as smooth, white, nonhemolytic colonies. The organism was not inhibited by colistin, kanamycin, or vancomycin and hydrolyzed esculin. The most likely identification of this isolate is which of the following? a. Fusobacterium nucleatum b. Fusobacterium varium c. Bacteroides fragilis d. Prevotella melaninogenica

c. Bacteroides fragilis

Pseudomembranous colitis caused by Clostridium difficile is best confirmed by which of the following laboratory findings? a. Presence of the toxin in stool b. Isolation of C. difficile from stool c. Gas production in thioglycolate media d. Gram stain of stool showing many gram-positive bacilli

a. Presence of the toxin in stool

Lecithinase production, double zone hemolysis on sheep blood agar, and gram-stained morphology are all useful criteria in the identification of which of the following? a. Clostridium perfringens b. Streptococcus agalactiae c. Escherichia coli d. Clostridium tetani

a. Clostridium perfringens

When activating a hydrogen and carbon dioxide generator system used for creating an anaerobic atmosphere, which of the following is an indication that the catalyst and generator envelope are functioning properly? a. A decrease in temperature of the jar b. Bubble formation on the surface of the plates c. A change in color of the methylene blue indicator d. The formation of a visible cloud of gas

c. A change in color of the methylene blue indicator

In a clinical specimen, the presence of sulfur granules strongly indicates the presence of which anaerobic bacterium? a. Bacteroides fragilis b. Actinomyces spp. c. Fusobacterium nucleatum d. Clostridium tetani

b. Actinomyces spp.

Which of the following are a common element between using the E test and agar disk diffusion (Kirby-Bauer) for antimicrobial susceptibility testing? a. Both establish an antibiotic gradient in agar b. Both create a circular zone of bacterial inhibition c. Expression of results is by MIC for both d. The cost of the test is similar per drug

a. Both establish an antibiotic gradient in agar

Which of the following clinical indications would most benefit from having quantitative (MIC) testing rather than qualitative (Sensitive, Intermediate, Resistant catagories) data from the laboratory? a. Urinary tract infection b. Bacterial meningitis c. Pneumonia caused by Mycoplasma d. Streptococcal pharyngitis

b. Bacterial meningitis

When performing antimicrobial susceptibility testing, the following definition of the minimum inhibitory concentration (MIC) is correct: a. The highest concentration of an antibiotic in a dilution series that inhibits growth b. The lowest concentration of an antibiotic in a dilution series that inhibits growth c. The lowest concentration of an antibiotic in a dilution series that kills the bacteria d. The lowest concentration of the antibiotic obtainable in the patient without toxicity

b. The lowest concentration of an antibiotic in a dilution series that inhibits growth

In comparing quantitative MIC dilution testing to qualitative agar disk diffusion testing, the higher the MIC of the drug for that organism: a. The smaller is the zone of inhibition b. The more susceptible the organism will appear on disk diffusion c. The larger is the zone of inhibition d. The more toxic is the drug to the patient

c. The larger is the zone of inhibition

In a quality control (QC) procedure on a new batch of Mueller-Hinton plates using a standard QC stock strain of Staphylococcus aureus, the disk inhibition zone sizes for three of the drugs tested were too small and fell below the expected QC range. Which of the following is the most likely reason for this observation? a. These three antibiotic disks were outdated and had lost potency b. These three disks were faulty in that the antibiotic content was too high c. Bacterial suspension of Staphylococcus was probably contaminated with another organism d. The plates received insufficient incubation time

a. These three antibiotic disks were outdated and had lost potency

Which of the following definitions best fit the term urethritis? a. Infection and or inflammation of the terminal portion of the lower urinary tract b. The isolation of a specified quantitative count of bacteria in an appropriately collected urine specimen obtained from a person without symptoms or signs of urinary infection c. Dysuria, frequency, and urgency but yielding fewer organisms than 105 colony-forming units of bacteria per milliliter (CFU/mL) urine on culture d. Inflammation of the kidney parenchyma, calices (cup-shaped division of the renal pelvis), and pelvis

a. Infection and or inflammation of the terminal portion of the lower urinary tract

The organism most commonly associated with otitis media infections is associated with which of the following positive test results? a. Coagulase b. VP c. Optochin d. Bacitracin

c. Optochin

Which organism is most often responsible for impetigo? a. Staphylococcus epidermidis b. Streptococcus pyogenes c. Enterococcus faecalis d. Streptococcus agalactiae

b. Streptococcus pyogenes

How do staphylococci spread so easily when infecting the skin? a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue b. They produce lipase, which melts the fat under the skin, making it easier to spread c. The hemolysins kill the white and red blood cells; then the protease liquefies the skin protein, allowing easy penetration for the bacteria d. All of the above

a. They produce hyaluronidase, which hydrolyzes hyaluronic acid present in the intracellular ground substance that makes up connective tissue

Routine culture media for use with a specimen of cerebrospinal fluid should include which of the following sets of media? a. 5% sheep blood agar, Lowenstein Jensen agar, 7H9 agar b. 5% sheep blood agar, thioglycolate broth c. 5% sheep blood agar, MacConkey agar, Sabourad dextrose agar d. 5% sheep blood agar, chocolate agar, thioglycolate broth

d. 5% sheep blood agar, chocolate agar, thioglycolate broth

A college student is examined at the emergency department; he is disoriented with a fever, intense headache, stiff neck, vomiting, and sensitivity to light. His friends say that he has been sick for about 2 days and that his condition worsened over the last 3 hours. The physician does a complete blood count (CBC) and electrolytes. The electrolytes are normal, but the patient’s white blood count (WBC) is 12,000 cells/L. What test should the doctor order next? a. Urine culture b. Stool culture c. Cerebrospinal fluid Gram stain and culture d. Blood culture

c. Cerebrospinal fluid Gram stain and culture

What cells are found in bacterial vaginosis? a. Clue cells b. Lymphocytes c. Macrophages d. Squamous epithelial cells

a. Clue cells

Which of the following terms is used to describe an increase of lymphocytes and other mononuclear cells (pleocytosis) in the cerebrospinal fluid and negative bacterial and fungal cultures? a. Meningoencephalitis b. Aseptic meningitis c. Encephalitis d. Meningitis

b. Aseptic meningitis

The culture of which sample routinely uses quantitation or the counting of bacterial cells present to assist in the interpretation? a. Blood b. Sputum c. Urine d. Abscess

c. Urine

Gram staining and reading a glass slide with a mixed smear of Staphylococcus and Escherichia coli along with each Gram staining run of specimens examined within the microbiology laboratory that day is an example of which of the following? a. Quality assurance (QA) activity b. Quality control (QC) activity c. National regulatory activity d. Office of Safety and Health Administration activity

b. Quality control (QC) activity

Tracking the rate of skin organism contamination among a laboratory’s blood culture results on a monthly basis and introducing specific training to phlebotomists when rates exceed the norm would be an example of which of the following? a. Good laboratory practice b. Quality control c. Universal standards d. Quality assurance

d. Quality assurance

Which of the following statements best defines “infectious substances”? a. Articles or substances capable of posing a risk to safety b. Substances known or reasonably expected to contain pathogens c. Patient samples containing bacteria d. Samples with class 3 pathogens

b. Substances known or reasonably expected to contain pathogens

Which of the following is an example of an inappropriate specimen or condition that would warrant rejection for microbiology culture? a. A nonsterile container for a stool culture b. A swab of a skin and soft tissue infection c. A tissue sample for anaerobic culture d. A 24-hour urine sample for bacteriology culture

d. A 24-hour urine sample for bacteriology culture

Which of the following terms is best described as the process of reproduction in yeast that begins with a weakening and outpouching of the yeast cell wall and then formation of a cell wall septum between the mother and daughter yeast cells? a. Binary fission b. Unisexual division c. Budding d. Outpouch germing

c. Budding

The loose intertwined network of basic structural units of the molds that penetrates the substrate from which it obtains the necessary nutrients for growth is called which of the following? a. Hyphae b. Germ tubes c. Pseudohyphae d. Mycelium

d. Mycelium

The term hyaline molds is used to describe which of the following? a. Molds that have septate hyphae b. Molds that have septate, nonpigmented hyphae c. The presence of pigmentation within the hyphae or the spores d. Molds with intercalated hyaline chlamydoconidia

c. The presence of pigmentation within the hyphae or the spores

Large, usually multi septate and club-shaped or spindle shaped spores are called which of the following? a. Microconidia b. Macroconidia c. Conidiophores d. Phialides

b. Macroconidia

A Scotch tape preparation is made from a mold growing on solid media in the mycology laboratory. The structure shown in the image is best described as which of the following? a. Sporangium b. Blastoconidia c. Ascospores d. Conidiophore

d. Conidiophore

A patient with a Wood’s lamp–positive, dermatophytic infection has a skin scraping taken for culture. The organism grows on SDA agar with a light-tan front and salmon-colored reverse. Microscopically the organism produces rare distorted macroconidia and rare microconidia. Additionally, there was no growth on sterile rice media. What is the most likely organism? a. Microsporum canis b. Microsporum gypseum c. Microsporum audouinii d. Epidermophyton floccosum

c. Microsporum audouinii

A KOH preparation of respiratory secretions of a 78- year-old man reveals large, spherical, thick-walled yeast cells 8 to 15 mm in diameter, usually with a single bud that is connected to the parent cell by a broad base. Which fungus will likely be isolated from the culture? a. Coccidioides immitis b. Blastomyces dermatitidis c. Histoplasma capsulatum d. Paracoccidioides brasiliensis

b. Blastomyces dermatitidis

Which of the following is a key characteristic of Coccidioides immitis? a. Has a higher dissemination rate in white females b. Is endemic in the northeastern United States c. Produces endosporulating spherules in tissue d. Forms foot cells

c. Produces endosporulating spherules in tissue

Using PAS to stain a respiratory specimen from a patient with lung disease, the technologists observed the organisms in the image. Based on the microscopic morphology shown in the image, the most likely identification of the dimorphic fungi is which of the following? a. Blastomyces dermatitidis b. Coccidioides immitis c. Histoplasma capsulatum d. Sporothrix schenckii

a. Blastomyces dermatitidis

A landscaper noticed a hard, unmovable lump under the skin of his index finger but decided to ignore it. A month later, the lump ulcerated to present a necrotic appearance, and two more lesions developed further up the wrist and forearm. A histologic stain of material from deep in the lesions showed elongated yeast cells resembling cigars. What disease is suspected?' a. Mycetoma b. Sporotrichosis c. Chromoblastomycosis d. Blastomycosis

b. Sporotrichosis

A germ tube–negative yeast is isolated in the laboratory. The isolate is found to be negative for urease and unable to assimilate dextrose, maltose, or sucrose. CMT agar morphology showed blastoconidia only. The organism is most likely: a. Candida albicans b. Candida parapsilosis c. Torulopsis glabrata d. Geotrichum candidum

c. Torulopsis glabrata

Which of the following is a key characteristic by which an unknown Cryptococcus spp. can be identified as Cryptococcus neoformans? a. Appearance of yellow colonies b. Positive urease test c. Presence of a capsule d. Positive niger seed agar test

d. Positive niger seed agar test

Which of the following statements concerning the germ tube test is true? a. Using a heavy inoculum enhances the rapid production of germ tubes b. Germ tubes should be read after 2 hours of incubation at 25C c. Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively d. Serum will be stable for 1 year if stored at room temperature

c. Candida albicans and Candida tropicalis can be used as positive and negative controls, respectively

An immunocompromised patient exhibited fever, nonproductive cough, and shortness of breath. Routine and fungal cultures did not grow. The respiratory specimen was stained with a silver stain in anatomic pathology. Based on the microscopic morphology in the image, what is the most likely identification of this organism? a. Pneumocystis jiroveci b. Saccharomyces sp. c. Candida albicans d. Cryptococcus sp.

a. Pneumocystis jiroveci

A significant amount of yeast was isolated from a vaginal culture of a patient in the teen clinic of your hospital. It exhibited the following characteristics: Microscopic: Clusters of blastoconidia along pseudohyphae, terminal chlamydoconidia Positive germ tube Positive sucrose Which of the following is the most likely identification of this fungi? (Image from primary plate, gram-stained smear, 40".) a. Rhodotorula rubra b. Candida albicans c. Geotrichum candidum d. Trichosporon beigelii

b. Candida albicans

The pharmacy at your hospital was concerned about the hyperalimentation fluid they were preparing. The high lipid contact was a concern for contamination. A PAS stain of the suspect fluid is shown. Which of the following organism would most likely demonstrate this morphology? a. Candida albicans b. Malassezia furfur c. Trichosporon cutaneum d. Scedosporium apiospermum

b. Malassezia furfur

Several important types of conidiation of dematiaceous fungi exist. The image is an example of which one of these forms? (Lactophenol cotton blue stain.) a. Cladosporium type b. Phialophora type c. Rhinocladiella type d. Rinderpest type

c. Rhinocladiella type

A mold isolated in the laboratory displays a white cottony macroscopic morphology. On microscopic evaluation, hyaline, septate hyphae, and “toothbrush”-like conidiophres are seen. The most likely organism is which of the following? a. Aspergillus sp. b. Acremonium sp. c. Gliocladium sp. d. Scopulariopsis sp.

b. Acremonium sp.

A mold is isolated in the laboratory that displays a velvety, gray-green colony morphology. On microscopic evaluation, flask-shaped conidiophores arranged in a brushlike formation are seen. The most likely organism is which of the following? a. Penicillium sp. b. Acremonium sp. c. Paecilomyces sp. d. Scopulariopsis sp.

a. Penicillium sp.

A patient who underwent solid organ transplant appears to have systemic fungemia. The organism that has grown from the blood cultures macroscopically had a blue-green color to the colony, matured in 3 days, and grew well at 45C. Microscopically, foot cells were seen and the phialides were uniserate with a round vesicle and columnar conidia. Which of the following is the most likely identification of this mold? a. Aspergillus fumigatus b. Aspergillus niger c. Scopulariopsis sp. d. Fusarium sp.

a. Aspergillus fumigatus

The protein coat that surrounds the nucleic acid of a virion is called which of the following? a. Capsomere b. Capsid c. Capsule d. Nucleocapsid

b. Capsid

During viral assembly, how are viral envelopes acquired? a. By production of envelope constituents by host cellular DNA b. As the virion buds from a host cell membrane c. Through replication of viral nucleic acid d. As host cell lysis produces many membrane fragments

b. As the virion buds from a host cell membrane

Prions are best described by which of the following? a. Infectious viral RNA without capsid proteins b. Infectious protein with no associated nucleic acid c. Infectious viral DNA without capsid proteins d. Nonenveloped virus highly resistant to heat and chemical inactivation

b. Infectious protein with no associated nucleic acid

The viral nucleocapsid always contains which of the following? a. Viral genome b. Virus-encoded glycoprotein c. Virus-encoded polymerase d. Viral envelope

a. Viral genome

Which of the following viruses are thought to predominately cause gastroenteritis? a. Hepadnaviruses b. Filoviruses c. Noroviruses d. Arboviruses

c. Noroviruses

Which of the following groups contains the SARS virus? a. Calicivirus b. Coronavirus c. Flavivirus d. Filovirus

b. Coronavirus

Which of the following groups of virus is best described as: ssRNA, enveloped, Pleomorphic/spherical capsid Large club-shaped spikes on surface gives “corona” effect Causes approximately 15% of coldlike illness a. Influenza A b. Influenza B c. Coronaviruses d. Pneumovirus

c. Coronaviruses

Which of the following is the specimen of choice for detecting rotavirus? a. Throat swab b. Urine sample c. Bronchoalveolar wash d. Feces sample

d. Feces sample

The test of choice and most sensitive assay for use with CSF to diagnose aseptic meningitis caused by enterovirus is which of the following? a. Cell culture b. PCR c. Antigenemia immunoassay d. Shell vial assay

b. PCR

A specimen from a genital lesion was inoculated into a standard set of cells for virus isolation. On day 1 the human foreskin fibroblasts exhibited the CPE shown in the figure. a. Herpes simplex virus b. Adenovirus c. Cytomegalovirus d. Epstein-Barr virus

a. Herpes simplex virus

Trophozoite forms of amoebae are found in what type of stool specimen? a. Formed b. Loose c. Soft d. Watery

d. Watery

Which preservation method is most suitable and the most widely used for subsequent fixed smear preparation? a. Formalin-ethyl acetate b. PVA c. Trichrome d. MIF

b. PVA

If the ova of this parasite are ingested by humans, the oncosphere form can migrate through the body via the bloodstream, resulting in the condition known as cysticercosis. Which of the following is correct? a. Taenia solium b. Entamoeba histolytica c. Hymenolepis nana d. Clonorchis sinensis

a. Taenia solium

Ova recovered from the stool are routinely used to diagnose infections caused by all of the following except? a. Necator americanus b. Ascaris lubricoides c. Trichuris trichiura d. Strongyloides stercoralis

d. Strongyloides stercoralis

An MLS finds an E. coli cyst on a wet mount of a fresh stool specimen. Which of the following should be done? a. Request a second specimen b. Look for additional E. coli cysts c. Examine the remaining area of the wet preparation d. Generate a final report

c. Examine the remaining area of the wet preparation

Which of the following parasites have migration through the lungs as part of their lifecycle? a. Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis b. Giardia lamblia, Wuchereria bancrofti, Brugia malayi c. Enterobius vermicularis, Trichuris trichiura, Trichinella spiralis d. Toxocara canis, Toxoplasma gondii, Blastocystis hominis

a. Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis

The image below is of a suspected parasite seen on direct examination of material taken from a corneal scraping in an ophthalmology clinic. The most likely identification of the parasite in this specimen is which of the following? a. Acanthamoeba sp. b. Enterobius sp. c. Paragonimus sp. d. Naegleria sp.

a. Acanthamoeba sp.

The organism shown below was recovered from the stool of a patient who resides in rural Texas. The most likely identification is which of the following? a. Ascaris lumbricoides b. Ancyclostoma duodenale c. Necator americanus d. Trichuris trichiura

d. Trichuris trichiura

The eggs in the figure below were found in the urine of a Peace Corp worker who had just returned to the United State after spending 2 years in the Middle East. The eggs measured about 160 mm longx60 mm wide. Which of the following organisms is the most likely identity? a. Diphyllobothrium latum b. Schistosoma haematobium c. Schistosoma japonicum d. Schistosoma mansoni

b. Schistosoma haematobium

A patient was diagnosed with cysts in his liver. He is originally from Australia, where he was involved in a sheep herding operation. The adult parasite shown below was passed by his pet dog. It measured 5 mm. What is the most likely identification of this organism? a. Diphyllobothrium latum b. Dipylidium caninum c. Echinococcus granulosus d. Taenia solium

c. Echinococcus granulosus

These trophozoites were found in a trichrome stained slide of a stool sample, measuring an average of 25 microns in diameter. Which of the following is the most likely identity of this organism? a. Endolimax nana b. Entamoeba coli c. Balantidium coli d. Dientamoeba fragilis

b. Entamoeba coli

The cyst in the image below was observed in a stool sample of a child at a daycare center. The ovoid cyst measures approximately 10!8 microns. Which organism is the most likely cause of the child’s diarrhea? a. Chilomastix mesnili b. Cyclospora cayetanensis c. Giardia lamblia d. Iodamoeba butschlii

c. Giardia lamblia

The image below is a cyst found in a human fecal smear. The cyst measured about 12 mm in length and contained four nuclei and a rounded chromatoid bar. The patient had severe diarrhea and some blood in the stool. What is the most likely identification of this organism? a. Endolimax nana b. Entamoeba coli c. Entamoeba histolytica d. Iodamoeba butschlii

c. Entamoeba histolytica

Match the parasite with the most appropriate description. _____ Plasmodium falciparum _____ Plasmodium malariae _____ Plasmodium ovale _____ Plasmodium vivax a. RBC enlarged, oval, Schuffner’s dots, gametocytes seen by day 4 to 18 b. Large RBC, troph irregular, multiple phases seen, gametocytes appear early c. Delicate ring forms, multiple rings per cell, crescent-shaped gametocytes after 7 to 10 days d. RBC normal in size and color, troph compact, band forms may be seen, gametocytes seen after weeks

c,d,a,b

Microfilariae found in the blood that have a sheath, demonstrate nocturnal periodicity and exhibit nuclei that do not extend to the tail tip are which of the following? a. Brugia malayi b. Onchocerca volvulus c. Loa loa d. Wuchereria bancrofti

d. Wuchereria bancrofti

Necator americanus rhabditiform larvae can be differentiated from Strongyloides stercoralis rhabditiform larvae by: a. Length of the notched tail b. Length of the head region c. Segmentation d. Size of the genital primordium

d. Size of the genital primordium

The image below is from a fecal smear of an individual complaining of diarrhea and intestinal discomfort. The parasites were numerous and quite variable in size, but the majority measured about 15 to 20 mm in diameter. What is the most likely identification of this organism? a. Blastocystis hominis b. Cyclospora cayetanensis c. Isospora belli d. Balantidium coli

a. Blastocystis hominis

Match the scientific name with the correspondingcommon name. _____ Sarcoptes scabei _____ Ixodes scapularis _____ P. humanus humanus _____ Cimex lectularius a. Body louse b. Bedbug c. Scabies d. Lyme disease

c;d;a;b

The only known human tapeworm with an operculum is: a. Diphyllobothrium latum b. Hymenolepis nana c. Giardia lamblia d. Schistosoma haematobium

a. Diphyllobothrium latum

Identify the following organism as it appears in this peripheral blood smear. a. Trypanosoma sp. b. Leishmania sp. c. Wuchereria bancrofti d. Loa loa

a. Trypanosoma sp.