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:

Options :

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 trial is evaluating the efficacy of a new antifungal agent against invasive aspergillosis. Serum galactomannan levels are being used as a biomarker to monitor the infection. A decrease in galactomannan levels during treatment would indicate:

Options :

A : Development of resistance to the antifungal agent.

B : Successful clearance or reduction of the Aspergillus burden.

C : A false-positive result in the galactomannan assay.

D : Concurrent infection with a non-Aspergillus mold.

Answer: B

Question 3

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?

Options :

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 4

Which biosafety level (BSL) is required for clinical laboratory work involving the propagation (culture) of Coccidioides immitis/posadasii?

Options :

A : BSL-1

B : BSL-2

C : BSL-3

D : BSL-4

Answer: C

Question 5

A patient develops a vesicular rash on their hands and feet, accompanied by fever and oral ulcers. The MOST likely causative agent is:

Options :

A : Varicella-zoster virus

B : Herpes simplex virus

C : Coxsackievirus A

D : Measles virus

Answer: C