©Jason MacConnell 2025 ALL RIGHTS RESERVED.
BOC: Microbiology Exam Questions With
Correct Answers A+
>100,000 CFU/mL of a gram-negative bacilli were isolated on MacConkey from a urine
specimen. Biochemical results are as follows:
Glucose: acid, gas produced
Indole: negative
Urea: positive
TDA: positive
H₂S: positive
The organism is most likely:
Morganella morganii
Proteus mirabilis
Proteus vulgaris
Providencia stuartii - Answer✔Proteus mirabilis
Susceptibility tsting is performed on a Staphylococcus aureus isolate from a blood culture with
the following results:
Oxacillin: Resisitant
Cefazolin: Susceptible
Clindamycin: Susceptible
Erythromycin: Susceptible
Trimethoprim/Sulfamethoxazole: Susceptible
Vancomycin: Susceptible
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
What should the technologist do next?
Ceftraixone should be reported instead of cefazolin
Clindamycin should be tested for inducible resistance prior to reporting
The trimethoprim/sulfamethoxazole result should be removed since all S aureus are resistant
The cefazolin result should be changed to resistant since the oxacillin result is resistant -
Answer✔The cefazolin result should be changed to resistant since the oxacillin result is resistant
Proper media for culture of a urethral discharge from a man:
Sheep blood and phenyl ethyl alcohol agars
Eosin-methylene blue and sheep blood agars
Thioglycollate broth and chocolate agar
Chocolate and modified Thayer-Martin agars - Answer✔Chocolate and modified Thayer-Martin
agars
A sheep blood agar plate inoculated with 0.001 mL of urine grows 70 colonies of
Staphylococcus aureus. How many colony forming units per mL of urine should be reported?
70
700
7,000
70,000 - Answer✔70,000
The lowest concentration of antibiotic that inhibits growth of a test organism:
Minimum inhibitory concentration
Serum inhibitory concentration
Minimum bactericidal titer
Maximum inhibitory titer - Answer✔Minimum inhibitory concentration
Which of the following clean catch urine culture colony counts indicates the patient likely has a
urinary tract infection?
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
10¹ CFU/mL
10³ CFU/mL
10⁵ CFU/mL
No growth - Answer✔10³ CFU/mL
The steam autoclave method of sterilization:
Uses 15 lbs of pressure for 15 minutes
Utilizes dry heat for 20 minutes
Produces a maximum temperature of 100°C
Requires a source of ethylene oxide - Answer✔Uses 15 lbs of pressure for 15 minutes
The expected colony count in a suprapubic urine from a healthy individual is:
0 CFU/mL
100 CFU/mL
1,000 CFU/mL
100,000 CFU/mL - Answer✔0 CFU/mL
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):
Nonfermenter
Obligate anaerobe
Aerobe
Facultative anaerobe - Answer✔Facultative anaerobe
A penicillin-resistant Neisseria gonorrhoeae produces:
Alpha-hemolysin
Beta-lactamase
Enterotoxin
Coagulase - Answer✔Beta-lactamase
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
Which selective medium is used for the isolation of gram-positive microorganisms?
Columbia CNA with 5% sheep blood
Trypticase soy agar with 5% sheep blood
Eosin methylene blue
Modified Thayer-Martin - Answer✔Columbia CNA with 5% sheep blood
The most sensitive substrate for the detection of beta-lactamase is:
Penicillin
Ampicillin
Cefoxitin
Nitrocefin - Answer✔Nitrocefin
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should be:
Screened for high level aminoglycoside resistance
Checked for tolerance
Assayed for serum antimicrobial activity
Tested for beta-lactamase production - Answer✔Screened for high level aminoglycoside
resistance
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
Incubation temperature
Duration of incubation
Cation content of media
Depth of agar - Answer✔Cation content of media
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
BOC: Microbiology Exam Questions With
Correct Answers A+
>100,000 CFU/mL of a gram-negative bacilli were isolated on MacConkey from a urine
specimen. Biochemical results are as follows:
Glucose: acid, gas produced
Indole: negative
Urea: positive
TDA: positive
H₂S: positive
The organism is most likely:
Morganella morganii
Proteus mirabilis
Proteus vulgaris
Providencia stuartii - Answer✔Proteus mirabilis
Susceptibility tsting is performed on a Staphylococcus aureus isolate from a blood culture with
the following results:
Oxacillin: Resisitant
Cefazolin: Susceptible
Clindamycin: Susceptible
Erythromycin: Susceptible
Trimethoprim/Sulfamethoxazole: Susceptible
Vancomycin: Susceptible
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
What should the technologist do next?
Ceftraixone should be reported instead of cefazolin
Clindamycin should be tested for inducible resistance prior to reporting
The trimethoprim/sulfamethoxazole result should be removed since all S aureus are resistant
The cefazolin result should be changed to resistant since the oxacillin result is resistant -
Answer✔The cefazolin result should be changed to resistant since the oxacillin result is resistant
Proper media for culture of a urethral discharge from a man:
Sheep blood and phenyl ethyl alcohol agars
Eosin-methylene blue and sheep blood agars
Thioglycollate broth and chocolate agar
Chocolate and modified Thayer-Martin agars - Answer✔Chocolate and modified Thayer-Martin
agars
A sheep blood agar plate inoculated with 0.001 mL of urine grows 70 colonies of
Staphylococcus aureus. How many colony forming units per mL of urine should be reported?
70
700
7,000
70,000 - Answer✔70,000
The lowest concentration of antibiotic that inhibits growth of a test organism:
Minimum inhibitory concentration
Serum inhibitory concentration
Minimum bactericidal titer
Maximum inhibitory titer - Answer✔Minimum inhibitory concentration
Which of the following clean catch urine culture colony counts indicates the patient likely has a
urinary tract infection?
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
10¹ CFU/mL
10³ CFU/mL
10⁵ CFU/mL
No growth - Answer✔10³ CFU/mL
The steam autoclave method of sterilization:
Uses 15 lbs of pressure for 15 minutes
Utilizes dry heat for 20 minutes
Produces a maximum temperature of 100°C
Requires a source of ethylene oxide - Answer✔Uses 15 lbs of pressure for 15 minutes
The expected colony count in a suprapubic urine from a healthy individual is:
0 CFU/mL
100 CFU/mL
1,000 CFU/mL
100,000 CFU/mL - Answer✔0 CFU/mL
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):
Nonfermenter
Obligate anaerobe
Aerobe
Facultative anaerobe - Answer✔Facultative anaerobe
A penicillin-resistant Neisseria gonorrhoeae produces:
Alpha-hemolysin
Beta-lactamase
Enterotoxin
Coagulase - Answer✔Beta-lactamase
, ©Jason MacConnell 2025 ALL RIGHTS RESERVED.
Which selective medium is used for the isolation of gram-positive microorganisms?
Columbia CNA with 5% sheep blood
Trypticase soy agar with 5% sheep blood
Eosin methylene blue
Modified Thayer-Martin - Answer✔Columbia CNA with 5% sheep blood
The most sensitive substrate for the detection of beta-lactamase is:
Penicillin
Ampicillin
Cefoxitin
Nitrocefin - Answer✔Nitrocefin
An Enterococcus isolated from multiple blood cultures in a patient endocarditis should be:
Screened for high level aminoglycoside resistance
Checked for tolerance
Assayed for serum antimicrobial activity
Tested for beta-lactamase production - Answer✔Screened for high level aminoglycoside
resistance
In the Kirby-Bauer disc diffusion susceptibility test, which variable is critical when testing
Pseudomonas species for antibiotic susceptibility to aminoglycosides?
Incubation temperature
Duration of incubation
Cation content of media
Depth of agar - Answer✔Cation content of media
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
