Free American Society for Microbiology ABMM Exam Questions

Question 1

A patient develops a severe diarrheal illness after consuming raw seafood. Stool culture yields a Gramnegative, comma-shaped bacterium that is oxidase-positive and grows on thiosulfate-citrate-bile salts-sucrose (TCBS) agar, producing blue-green colonies. The MOST significant virulence factor contributing to the severe, cholera-like diarrhea caused by this organism is:

A : Heat-stable enterotoxin (ST)

B : Heat-labile toxin (LT)

C : Cholera toxin (CT)-like enterotoxin

D : Type III secretion system (T3SS)

Answer: C

Question 2

A clinical isolate of Klebsiella pneumoniae from a patient with a refractory urinary tract infection exhibits resistance to carbapenems (imipenem, meropenem, ertapenem). PCR analysis reveals the presence of the blaKPC gene. Which of the following enzymatic mechanisms is responsible for this resistance?

A : Hydrolysis of the beta-lactam ring, leading to an inactive antibiotic derivative.

B : Modification of the ribosomal target site, preventing antibiotic binding.

C : Efflux of the carbapenem antibiotic out of the bacterial cell.

D : Trapping of the carbapenem molecule by a decoy protein.

Answer: A

Question 3

A research laboratory is investigating the mechanisms of viral latency in herpes simplex virus type 1 (HSV1). During latency in sensory neurons, the viral genome exists as a circular episome. Whichof the following viral gene products is thought to play a crucial role in maintaining this latent state and preventing viral gene expression?

A : Immediate-early (IE) proteins such as ICP4 and ICP27.

B : Early (E) proteins such as thymidine kinase and DNA polymerase.

C : Late (L) proteins such as structural glycoproteins.

D : Latency-associated transcripts (LATs).

Answer: D

Question 4

A patient develops a severe diarrheal illness after consuming raw seafood. Stool culture yields a Gramnegative, comma-shaped bacterium that is oxidase-positive and grows on thiosulfate-citrate-bile salts-sucrose (TCBS) agar, producing blue-green colonies. The MOST significant virulence factor contributing to the severe, cholera-like diarrhea caused by this organism is:

A : Heat-stable enterotoxin (ST)

B : Heat-labile toxin (LT)

C : Cholera toxin (CT)-like enterotoxin

D : Type III secretion system (T3SS)

Answer: C

Question 5

A microbiology laboratory is processing a stool sample for ova and parasites. A large (approximately 100 µm), thick-shelled, oval egg with a flattened side is observed. This egg MOST likely belongs to:

A : Ascaris lumbricoides

B : Enterobius vermicularis

C : Taenia species

D : Trichuris trichiura

Answer: A