ABPath Medical Microbiology 3

Question 1

Which organism produces a green pigment (pyocyanin) and a grape-like odor in culture?

Accepted Answer

Pseudomonas aeruginosa

Answer

P. aeruginosa produces pyocyanin and a fruity/grape-like odor.

Question 2

A stool culture on sorbitol-MacConkey shows sorbitol-nonfermenting colonies. Which pathogen is suspected?

Accepted Answer

E. coli O157:H7

Answer

E. coli O157:H7 does not ferment sorbitol, distinguishing it on SMAC agar.

Question 3

Which encapsulated yeast stains with India ink in CSF and causes meningitis in AIDS patients?

Accepted Answer

Cryptococcus neoformans

Answer

Cryptococcus has a polysaccharide capsule visualized by India ink.

Question 4

Which bacterium is the most common cause of hospital-acquired Clostridioides difficile risk after broad-spectrum antibiotics?

Accepted Answer

Clostridioides difficile

Answer

C. difficile overgrows after antibiotic disruption of normal flora, causing pseudomembranous colitis.

Question 5

A blood culture grows lactose-fermenting, mucoid, string-test-negative gram-negative rods. Which organism?

Accepted Answer

Klebsiella pneumoniae

Answer

Klebsiella is a mucoid, lactose-fermenting gram-negative rod due to its prominent capsule.

American Board of Pathology (ABPath) Practice Test