EXAM 4 MICROBIOLOGY UAMS
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS ALREADY
PASSED!!!
Microbiology: Specimen Processing, Media Selection & Blood Cultures
What three primary culture media plates are considered BEST for setting up
a routine sputum culture?
✔✔ Blood Agar Plate (BAP), MacConkey Agar (MAC), and Chocolate Agar
(CHOC)
(BAP supports both gram-positive and gram-negative growth and hemolysis; MAC
selects for Gram-negative enteric bacilli; CHOC provides X and V factors
necessary for fastidious respiratory pathogens like Haemophilus).
If three separate consecutive venipuncture blood culture sets yield
Corynebacterium species from a patient, can you clinically suspect that
Corynebacterium is the true pathogen rather than a mere skin contaminant?
✔✔ Yes.
(While single blood culture bottle contamination with skin flora
Corynebacterium—often diphtheroids—is common, growth across multiple/all
separate venipuncture sets strongly suggests true bacteremia or endocarditis,
especially in immunocompromised patients or those with indwelling devices).
What is the appropriate course of action when a clean-catch urine specimen is
submitted to the laboratory for an anaerobic culture?
✔✔ Reject the specimen.
(Reasoning: Urine is exposed to oxygen in the urinary tract, making it unsuitable
for anaerobes. Furthermore, voided urine specimens are routinely contaminated
by normal perineal and urethral flora containing anaerobes, rendering anaerobic
cultures clinically uninterpretable
QUESTIONS AND ANSWERS WITH
COMPLETE SOLUTIONS ALREADY
PASSED!!!
Microbiology: Specimen Processing, Media Selection & Blood Cultures
What three primary culture media plates are considered BEST for setting up
a routine sputum culture?
✔✔ Blood Agar Plate (BAP), MacConkey Agar (MAC), and Chocolate Agar
(CHOC)
(BAP supports both gram-positive and gram-negative growth and hemolysis; MAC
selects for Gram-negative enteric bacilli; CHOC provides X and V factors
necessary for fastidious respiratory pathogens like Haemophilus).
If three separate consecutive venipuncture blood culture sets yield
Corynebacterium species from a patient, can you clinically suspect that
Corynebacterium is the true pathogen rather than a mere skin contaminant?
✔✔ Yes.
(While single blood culture bottle contamination with skin flora
Corynebacterium—often diphtheroids—is common, growth across multiple/all
separate venipuncture sets strongly suggests true bacteremia or endocarditis,
especially in immunocompromised patients or those with indwelling devices).
What is the appropriate course of action when a clean-catch urine specimen is
submitted to the laboratory for an anaerobic culture?
✔✔ Reject the specimen.
(Reasoning: Urine is exposed to oxygen in the urinary tract, making it unsuitable
for anaerobes. Furthermore, voided urine specimens are routinely contaminated
by normal perineal and urethral flora containing anaerobes, rendering anaerobic
cultures clinically uninterpretable
