BOC Microbiology Exam Study Set-Questions with
100% Correct Answers | Verified
The expected colony count in a suprapubic urine from a healthy individual is:
A. 0 CFU/mL
B. 100 CFU/mL
C. 1,000 CFU/mL
D. 100,000 CFU/mL - ✔✔Correct Answer: A
An aspirate of a deep wound was plated on blood agar plates and incubated aerobically
and anaerobically. At 24 hours there was growth on both plates. This indicates that the
organism is a(n):
A. nonfermenter
B. obligate anaerobe
C. aerobe
D. facultative anaerobe - ✔✔Correct Answer: D
The proper blood-to-broth ratio for blood cultures to reduce the antibacterial effect of
serum in adults is:
A. 1:2
B. 1:3
C. 1:10
D. 1:30 - ✔✔Correct Answer: C
A penicillin-resistant Neisseria gonorrhoeae produces:
A. alpha-hemolysin
,B. beta-lactamase
C. enterotoxin
D. coagulase - ✔✔Correct Answer: B
Which selective medium is used for the isolation of gram-positive microorganism?
A. Columbia CNA with 5% sheep blood
B. trypticase soy agar with 5% sheep blood
C. eosin methylene blue
D. modified Thayer-Martin - ✔✔Correct Answer: A
The most sensitive substrate for the detection of beta-lactamases is:
A. penicillin
B. ampicillin
C. cefoxitin
D. nitrocefin - ✔✔Correct Answer: D
A Staphylococcus aureus isolate has an MIC of 4 ug/mL to oxacillin. There is uncertainty
as to whether this represents an oxacillin (heteroresistant) resistant strain or
hyperproducer of beta-lactamase.
Strain; Oxacillin; Amoxicillin-clavulanic acid
-Strain A: sus;sus
-Strain B: sus; res
-Stain C: res; sus
-Strain D: res; res
Based on the above results for oxacillin and amoxicillin-clavulanic acid, which strain is
heteroresistant?
,A. stain A
B. strain B
C. strain C
D. strain D - ✔✔Correct Answer: D
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
A. screened for high level aminoglycoside resistance
B. checked fo tolerance
C. assayed for serum antimicrobial activity
D. tested for beta-lactamase production - ✔✔Correct Answer: A
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
A. incubation temperature
B. duration of incubation
C. cation content of media
D. depth of agar - ✔✔Correct Answer: C
The procedure that assures the most accurate detection of mecA-mediated oxacillin
resistance in routine broth microdilution susceptibility testing against S. aureus is:
A. addition of 4% NaCl
B. incubation at 30 C
C. incubation for 48 hours
D. use of cefoxitin for testing - ✔✔Correct Answer: D
, When performing a stool culture, a colony type typical of an enteric pathogen is
subcultured on a blood agar plate. The resulting pure culture is screened with several
tests to obtain the following results:
-TSI: acid butt, alkaline slant, no gas, no H2S
-phenylalanine deaminase: negative
-motility: positive
-serological typing: Shigella flexneri (shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
A. report the organism as Shigella flexneri without further testing
B. verify reactivity of motility medium with positive and negative controls
C. verify reactivity of the TSI slants with positive and negative controls for H2S
production
D. verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Correct Answer: B
Susceptibility testing performed on quality control organism using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
A. the antibiotic disks were not stored with the proper desiccant
B. the depth of the media was too thick
C. the depth of the media was too thin
D. the antibiotic disks were not properly applied to the media - ✔✔Correct Answer: C
Three sets of blood cultures were obtained form an adult patient with fever and
suspected endocariditis. The aerobic bottle of one set had growth of Staphylococcus
epidermidis at 5 days of incubation. this indicates that:
A. there was low-grade bacteremia
100% Correct Answers | Verified
The expected colony count in a suprapubic urine from a healthy individual is:
A. 0 CFU/mL
B. 100 CFU/mL
C. 1,000 CFU/mL
D. 100,000 CFU/mL - ✔✔Correct Answer: A
An aspirate of a deep wound was plated on blood agar plates and incubated aerobically
and anaerobically. At 24 hours there was growth on both plates. This indicates that the
organism is a(n):
A. nonfermenter
B. obligate anaerobe
C. aerobe
D. facultative anaerobe - ✔✔Correct Answer: D
The proper blood-to-broth ratio for blood cultures to reduce the antibacterial effect of
serum in adults is:
A. 1:2
B. 1:3
C. 1:10
D. 1:30 - ✔✔Correct Answer: C
A penicillin-resistant Neisseria gonorrhoeae produces:
A. alpha-hemolysin
,B. beta-lactamase
C. enterotoxin
D. coagulase - ✔✔Correct Answer: B
Which selective medium is used for the isolation of gram-positive microorganism?
A. Columbia CNA with 5% sheep blood
B. trypticase soy agar with 5% sheep blood
C. eosin methylene blue
D. modified Thayer-Martin - ✔✔Correct Answer: A
The most sensitive substrate for the detection of beta-lactamases is:
A. penicillin
B. ampicillin
C. cefoxitin
D. nitrocefin - ✔✔Correct Answer: D
A Staphylococcus aureus isolate has an MIC of 4 ug/mL to oxacillin. There is uncertainty
as to whether this represents an oxacillin (heteroresistant) resistant strain or
hyperproducer of beta-lactamase.
Strain; Oxacillin; Amoxicillin-clavulanic acid
-Strain A: sus;sus
-Strain B: sus; res
-Stain C: res; sus
-Strain D: res; res
Based on the above results for oxacillin and amoxicillin-clavulanic acid, which strain is
heteroresistant?
,A. stain A
B. strain B
C. strain C
D. strain D - ✔✔Correct Answer: D
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should
be:
A. screened for high level aminoglycoside resistance
B. checked fo tolerance
C. assayed for serum antimicrobial activity
D. tested for beta-lactamase production - ✔✔Correct Answer: A
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
A. incubation temperature
B. duration of incubation
C. cation content of media
D. depth of agar - ✔✔Correct Answer: C
The procedure that assures the most accurate detection of mecA-mediated oxacillin
resistance in routine broth microdilution susceptibility testing against S. aureus is:
A. addition of 4% NaCl
B. incubation at 30 C
C. incubation for 48 hours
D. use of cefoxitin for testing - ✔✔Correct Answer: D
, When performing a stool culture, a colony type typical of an enteric pathogen is
subcultured on a blood agar plate. The resulting pure culture is screened with several
tests to obtain the following results:
-TSI: acid butt, alkaline slant, no gas, no H2S
-phenylalanine deaminase: negative
-motility: positive
-serological typing: Shigella flexneri (shigella subgroup B)
The serological typing is verified with new kit and controls. The best course of action
would be to:
A. report the organism as Shigella flexneri without further testing
B. verify reactivity of motility medium with positive and negative controls
C. verify reactivity of the TSI slants with positive and negative controls for H2S
production
D. verify reactivity of phenylalanine deaminase with positive and negative controls -
✔✔Correct Answer: B
Susceptibility testing performed on quality control organism using a new media lot
number yielded zone sizes that were too large for all antibiotics tested. The testing was
repeated using media from a previously used lot number, and all zone sizes were
acceptable. Which of the following best explains the unacceptable zone sizes?
A. the antibiotic disks were not stored with the proper desiccant
B. the depth of the media was too thick
C. the depth of the media was too thin
D. the antibiotic disks were not properly applied to the media - ✔✔Correct Answer: C
Three sets of blood cultures were obtained form an adult patient with fever and
suspected endocariditis. The aerobic bottle of one set had growth of Staphylococcus
epidermidis at 5 days of incubation. this indicates that:
A. there was low-grade bacteremia
