PCAT Microbiology 5

Question 1

Which viral replication strategy characterizes retroviruses and is essential for their integration into the host genome?

Accepted Answer

RNA → DNA → integrated DNA → RNA

Answer

Retroviruses use reverse transcriptase to convert their RNA genome to dsDNA, which integrase then integrates into the host chromosome as proviral DNA.

Question 2

Coagulase production is used to differentiate Staphylococcus aureus from which of the following?

Accepted Answer

Staphylococcus epidermidis

Answer

S. aureus is coagulase-positive, while S. epidermidis and other coagulase-negative staphylococci lack this enzyme, making coagulase the key differentiating test.

Question 3

The quorum sensing mechanism in bacteria regulates gene expression based on:

Accepted Answer

Population density detected via signaling molecules

Answer

Quorum sensing uses secreted autoinducer molecules that accumulate with cell density; when a threshold is reached, they bind receptors and alter gene expression.

Question 4

Which characteristic of Mycobacterium tuberculosis allows it to survive within macrophage phagosomes?

Accepted Answer

Prevention of phagosome-lysosome fusion

Answer

M. tuberculosis arrests phagosome maturation, preventing acidification and fusion with lysosomes, allowing the bacterium to survive and replicate within macrophages.

Question 5

A patient develops watery diarrhea after antibiotic use; stool test shows Clostridioides difficile toxin. The toxins A and B primarily act by:

Accepted Answer

Inactivating Rho GTPases to disrupt the actin cytoskeleton

Answer

C. difficile toxins A and B glucosylate and inactivate Rho GTPases, disrupting actin dynamics, tight junctions, and epithelial barrier integrity.

PCAT - Pharmacy College Admission Test Practice Test

PCAT - Pharmacy College Admission Test Practice Test

PCAT Microbiology 5