©Jason MacConnell 2025 ALL RIGHTS RESERVED.
BOC Microbiology Exam Questions With
Correct Answers A+
Proper media for culture of a urethral discharge from a man include:
A. sheep blood and phenylethyl alcohol agars
B. eosin-methylene blue and sheep blood agars
C. thioglycollate broth and chocolate agar
D. chocolate and modified Thayer-Martin agars - Answer✔Correct Answer: D
A sheep blood agar plate inoculate with 0.001 mL, of urine grows 70 colonies of Staphylococcus
aureus. How many colony forming units per mL of urine should be reported?
A. 70
B. 700
C. 7,000
D. 70,000 - Answer✔Correct Answer: D
The lowest concentration of antibiotic that inhibit growth of a test organism is the:
A. minimum inhibitory concentration
B. serum inhibitory concentration
C. minimum bactericidal titer
D. maximum inhibitory titer - Answer✔Correct Answer: A
Which of the following clean catch urine culture colony counts indicates the patient likely has a
urinary tract infection?
A. 10^1 CFU/mL
B. 10^3 CFU/mL
C. 10^5 CFU/mL
D. no growth - Answer✔Correct Answer: B
The steam autoclave method of sterilization:
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
A. uses 15 lbs of pressure for 15 minutes
B. utilizes dry heat for 20 minutes
C. produces a maximum temperature of 100C
D. requires a source of ethylene oxide - Answer✔Correct Answer: A
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 - Answer✔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 - Answer✔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 - Answer✔Correct Answer: C
A penicillin-resistant Neisseria gonorrhoeae produces:
A. alpha-hemolysin
B. beta-lactamase
C. enterotoxin
D. coagulase - Answer✔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
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
C. eosin methylene blue
D. modified Thayer-Martin - Answer✔Correct Answer: A
The most sensitive substrate for the detection of beta-lactamases is:
A. penicillin
B. ampicillin
C. cefoxitin
D. nitrocefin - Answer✔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 - Answer✔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 - Answer✔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
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
D. depth of agar - Answer✔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 - Answer✔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 -
Answer✔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 - Answer✔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
BOC Microbiology Exam Questions With
Correct Answers A+
Proper media for culture of a urethral discharge from a man include:
A. sheep blood and phenylethyl alcohol agars
B. eosin-methylene blue and sheep blood agars
C. thioglycollate broth and chocolate agar
D. chocolate and modified Thayer-Martin agars - Answer✔Correct Answer: D
A sheep blood agar plate inoculate with 0.001 mL, of urine grows 70 colonies of Staphylococcus
aureus. How many colony forming units per mL of urine should be reported?
A. 70
B. 700
C. 7,000
D. 70,000 - Answer✔Correct Answer: D
The lowest concentration of antibiotic that inhibit growth of a test organism is the:
A. minimum inhibitory concentration
B. serum inhibitory concentration
C. minimum bactericidal titer
D. maximum inhibitory titer - Answer✔Correct Answer: A
Which of the following clean catch urine culture colony counts indicates the patient likely has a
urinary tract infection?
A. 10^1 CFU/mL
B. 10^3 CFU/mL
C. 10^5 CFU/mL
D. no growth - Answer✔Correct Answer: B
The steam autoclave method of sterilization:
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
A. uses 15 lbs of pressure for 15 minutes
B. utilizes dry heat for 20 minutes
C. produces a maximum temperature of 100C
D. requires a source of ethylene oxide - Answer✔Correct Answer: A
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 - Answer✔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 - Answer✔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 - Answer✔Correct Answer: C
A penicillin-resistant Neisseria gonorrhoeae produces:
A. alpha-hemolysin
B. beta-lactamase
C. enterotoxin
D. coagulase - Answer✔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
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
C. eosin methylene blue
D. modified Thayer-Martin - Answer✔Correct Answer: A
The most sensitive substrate for the detection of beta-lactamases is:
A. penicillin
B. ampicillin
C. cefoxitin
D. nitrocefin - Answer✔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 - Answer✔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 - Answer✔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
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
D. depth of agar - Answer✔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 - Answer✔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 -
Answer✔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 - Answer✔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
