8.12 Flashcards
An emergency department physician ordered a culture and sensitivity test on a catheterized urine specimen obtained from a 24-year-old female patient. A colony count was done and gave the following results after 24 hours:
-Blood agar plate=>100,000 col/mL of gram-positive cocci resembling staphylococci
-MacConkey agar=No growth
-Hemolysis=Neg
-Novobiocin=Resistant
-CNA plate=Inhibited growth
-Catalase=Positive
A. Staphylococcus saprophyticus
B. Micrococcus luteus
C. Staphylococcus aureus
D. Streptococcus pyogenes
A. Staphylococcus saprophyticus
An outbreak of Staphylococcus aureus in the nursery department prompted the Infection Control Committee to proceed with an environmental screening procedure. The best screening media to use for this purpose would be:
A. CNA agar
B. THIO broth
C. Mannitol salt agar
D. PEA agar
C. Mannitol salt agar
A listless 12-month-old boy with a fever of 103F was taken to the emergency department. He had been diagnosed with an ear infection 3 days earlier. A spinal tap was performed, but only one tube of CSF was obtained form the lumbar puncture. The single tube of CSF should be submitted first to which department?
A. Chemistry
B. Microbiology
C. Hematology
D. Cytology/Histology
B. Microbiology
A 65-year-old female outpatient was requested by her physician to submit a 24-hour urine specimen for protein and creatinine tests. He also requested testing for mycobacteria in the urine. Should the microbiology laboratory accept this 24-hour specimen for culture?
A. Yes, if the specimen is kept on ice
B. Yes, if the specimen is for aerobic culture only
C. No, the specimen must be kept at room temperature
D. No, the specimen is unsuitable for the recovery of mycobacteria
D. No, the specimen is unsuitable for the recovery of mycobacteria
A lymph node biopsy obtained form a 30-year-old male patient was submitted to the microbiology laboratory for a culture and AFB smear for mycobacteria. The specimen was fixed in formalin. This specimen should be:
A. Accepted for AFB smear and cultured
B. Rejected
C. Held at room temperature for 24 hours and then cultured
D. Cultured for anaerobes only
B. Rejected
A 49-year-old man who traveled to Mexico City returned with a bad case of dysentery. His symptoms were fever; abdominal cramping; and bloody, mucoidal, frequent stools. In addition to this, many WBCs were seen on the Gram stain smear. Stool culture gave the following results:
-Gram stain: Gram-negative rods
-Indole=+
-Urease=Neg
-Lactose=+
-Lysin decarboxylase=Neg
-Motility=Neg
What is the most likely organism?
A. Salmonella spp.
B. Proteus mirabilis
C. Escherichia coli
D. Enteroinvasive E. coli (EIEC)
D. Enteroinvasive E. coli (EIEC)
An 80-year-old male patient was admitted to the hospiral with a fever of 102F. A sputum culture revealed many gram-negative rods on MacConkey agar and blood agar. The patient was diagnosed with pneumonia. The following biochemical results were obtained form the culture:
-H2S=Neg
-Citrate=+
-Motility=Neg
-Lactose=+
-Indole=+
-Resistance to ampicillin and carbenicillin
-Urease=+
-VP=+
What is the most likely identification?
A. Klebsiella oxytoca
B. Proteus mirabilis
C. Escherichia coli
D. Klebsiella pneumoniae
A. Klebsiella oxytoca
An immunocompromised 58-year-old female chemotherapy patient received 2 units of packed RBCs. The patient died 3 days later, and the report from the autopsy revealed that her death was due to septic shock. The blood bags were cultured, and the following results were noted:
-GROWTH OF AEROBIC GRAM-NEGATIVE RODS ON BOTH MACCONKEY AND BLOOD AGARS
-Lactose=Neg
-Indole=Neg
-Urease=+
-Sucrose=+
-VP=Neg
-Motility 22C=+
-Citrate=Neg
-H2S=Neg
-Motility 37C=Neg
What is the most likely identification?
A. Escherichia coli
B. Yersinia entercolitica
C. Enterobacter cloacae
D. Citrobacter freundii
B. Yersinia entercolitica
A pediatric patient with severe bloody diarrhea who had been camping with his parents was admitted to the hospital with complications of hemolytic uremic syndrom (HUS). Several stool specimesn were cultured with the following results noted:
-Gram stain smear= Many gram-negative rods with no WBCs seen
-Blood agar=Normal flora
-MacConkey agar=Normal flora
-MacConkey agar with sorbitol=Many clear colonies (sorbitol negative)
-Hektoen agar=Normal flora
-Campy agar=No growth
What is the most likely identification?
A. Yersinia spp.
B. E. coli 0157:H7
C. Salmonella spp.
D. Shigella spp.
B. E. coli 0157:H7
A 14-year-old emergency department patient had been tothe doctor’s office 2 days previously with abdominal pain, diarrhea, and a low-grade fever. He was diagnosed with pseudoappendicular syndrome. Cultures form the stool containig blood and WBCs showed the following results:
AEROBIC GRAM-NEGATIVE RODS ON MACONKEY AGAR (CLEAR COLONIES)
-Campy agar=No growth
-Lactose=Neg
-Indole=Neg
-Motility 37C=Neg
-Sucrose=+
-VP=Neg
-Motility 22C=+
-Citrate=Neg
-H2S=Neg
-Hektoen agar=NF
What is the most likely identification?
A. Yersinia enterocolitica
B. Salmonella spp.
C. Shigella spp.
D. Escherichia coli
A. Yersinia enterocolitica
A sputum culture from a 13-year-old cystic fibrosis patient grew a predominance of short, gram-negative rods that tested oxidase negative. On MacConkey, chocolate, and blood agar plates, the organism appeared to have a lavender-green pigment. Further testing showed:
-Motility=+
-Glucose=+ (oxidative)
-Lysine decarboxylase=+
-DNase=+
-Maltose=+ (oxidative)
-Esculin hydrolysis=+
What is the most likely identification?
A. Stenotrophomonas maltophilia
B. Acinetobacter baumannii
C. Pseudomonas aeruginosa
D. Burkholderia (P.) cepacia
A. Stenotrophomonas maltophilia
A patient with a human bite wound on the right forearm arrived at the clinic for treatment. The wound was inflicted 36 hours earlier, and a culture was taken by the physician on duty. After 48 hours, the culture result were:
-Gram-stain smear=Gram-negative straight, slender rods
-Chocolate agar plate=”Pitting” of the agar by small, yellow, opaque colonies
-Oxidase=+
-Glucose=+
-Growth in increased CO2=+
-Motility=Neg
-Growth at 42C=Neg
What is the most likely identification of this facultative anaerobe?
A. Pseudomonas aeruginosa
B. Acinetobacter baumannii
C. Kingella kingae
D. Eikenella corrodens
D. Eikenella corrodens
A dog bit wound to the thumb of a 20-year-old male patient became infected. The culture grew a gram-negative, slender rod, which was a facultative anaerobe. The following results were note:
-Oxidase=+
-Catalase=+
-Motility=Neg
-Capnophilic=+
“Gliding” on the agar was noted. What is the most likely identification?
A. Pseudomonas aeruginosa
B. Capnocytophaga canimorsus
C. Acinetobacter baumannii
D. Proteus mirabilis
B. Capnocytophaga canimorsus
A patient exhibits fever, chills, abdominal cramps, diarrhea, vomiting, and bloody stools 10 to 12 hours after eating. Which organisms will most likely grow form this patient’s stool culture?
A. Salmonella or Yersinia spp.
B. E. coli 0157:H7 or Shigella spp.
C. Staphylococcus aureus or Clostridium perfringens
D. Salmonella or Staphylococcus
B. E. coli 0157:H7 or Shigella spp.
When testing for coagulase properties, staphylococci isolates from a 67-year-old male diabetic patient showed a positive tube test (free coagulase). The organism should be identified as:
A. Staphylococcus aureus
B. Staphylococcus haemolyticus
C. Staphylococcus saprophyticus
D. Micrococcus luteus
A. Staphylococcus aureus
An isolate of Staphylococcus aureus was cultured form an ulcer obtained form the leg of a diabetic 79-year-old female patient. The organism showed resistance to methicillin. Additional, this isolate should be tested for resistance or susceptibility to :
A. Erythromycin
B. Gentamicin
C. Vancomycin
D. Kanamycin
C. Vancomycin
An isolate recovered form a vaginal culture obtained form a 25-year-old female patient who is 8 months pregnant is who to be a gram-positive cocci, catalase negative, and B-hemolytic on blood agar. Which tests are needed for further identification?
A. Optochin, bile solubility, PYR
B. Bacitracin, CAMP, PYR
C. Methicillin, PYR, trehalose
D. Coagulase, glucose, PYR
B. Bacitracin, CAMP, PYR
Which organism is the most often recovered gram-positive cocci (catalase negative) from a series of blood cultures obtained from individuals with endocarditis?
A. Streptococcus agalactiae
B. Clostridium perfringens
C. Enterococcus faecalis
D. Pediococcus spp.
C. Enterococcus faecalis
A presumptive diagnosis of gonorrhea can be made from an exudate from a 20-year-old emergency department patient if which of the following criteria are present?
A. Smear of urethral exudate (male only) shoes typical gram-negative, intracellular diplococci; growth of oxidase-positive, gram-negative diplococci on selective agar (modified Thayer-Martin)
B. Smear from vaginal area shows gram-negative diplococci; growth of typical colonies on blood agar
C. Smear from rectum shows typical gram-negative diplococci; no growth on chocolate agar
D. Growth of gram-negative cocci on MacConkey agar and blood agar
A. Smear of urethral exudate (male only) shoes typical gram-negative, intracellular diplococci; growth of oxidase-positive, gram-negative diplococci on selective agar (modified Thayer-Martin)
“Clue cells” are seen on a smear of vaginal discharge obtained from an 18-year-old female emergency department patient. This finding, along with a fishy odor (amine) after the addition of 19% KOH, suggest bacterial vaginosis caused by which organism?
A. Staphylococcus epidermidis
B. Streptococcus agalactiae
C. Gardnerella vaginalis
D. E. coli
C. Gardnerella vaginalis
A 1-month-old infanct underwent a spinal tap to rule out bacterial meningitis. The CSF was cloudy, and the smear showed many pus cells and short gram-positive rods. After 18 hours, many colonies appeared on blood agar that resembled Streptococcus spp. or L. monocytogenes. Which of the following preliminary tests should be performed on the colonies to best differentiate L. monocytogenes from Streptococcus spp.?
A. Hanging-drop motility (25C) and catalase
B. PYR and bacitracin
C. Oxidase and glucose
D. Coagulase and catalase
A. Hanging-drop motility (25C) and catalase
Acid-fast positive bacilli were recovered form the sputum of a 79-year-old man who had been treated for pneumonia. Which of the following test reaction after 3 weeks of incubation on Lowenstein-Jensen agar are consistent with Mycobacterium tuberculosis?
A. Niacin=+; Nitrate reduction=+; Photochromogenic=Neg
B. Niacin=+; Optochin=+; Catalase=+
C. PYR=+; Urease=+; Bacitracin=+
D. Ampicillin=Resistant; Penicillin=Resistant;
A. Niacin=+; Nitrate reduction=+; Photochromogenic=Neg
Which biochemical tests should be performed in order to identify colorless colonies growing on MacConkey agar (swarming colonies on blood agar) from a catheterized urine specimen?
A. Indole, phenylalanine deaminase, and urease
B. Glucose, oxidase, and lactose utilization
C. Phenylalanine deaminase and bile solubility
D. H2S and catalase
A. Indole, phenylalanine deaminase, and urease
A gram-negative nonfermenter was isolated from a culture taken from a burn patient. Which of the following is the best choice of test to differentiate Pseudomonas aeruginosa form Acinetobacter spp.?
A. Growth on MacConkey agar, catalase, growth at 37C
B. Oxidase, motility, growth at 42C
C. Growth on blood agar, oxidase growth at 35C
D. String test and coagulase test
B. Oxidase, motility, growth at 42C
