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Microbiology Flashcards

7 cards from real PCAT practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.

Read the first 7 Microbiology flashcards as text

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

    Answer: RNA → DNA → integrated DNA → RNA

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

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

    Answer: Staphylococcus epidermidis

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

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

    Answer: Population density detected via signaling molecules

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

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

    Answer: Prevention of phagosome-lysosome fusion

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

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

    Answer: Inactivating Rho GTPases to disrupt the actin cytoskeleton

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

  6. Which antiviral mechanism of action is used by neuraminidase inhibitors (e.g., oseltamivir) in treating influenza?

    Answer: Inhibiting release of new virions from infected cells

    Neuraminidase inhibitors prevent influenza neuraminidase from cleaving sialic acid residues, trapping newly assembled virions on the infected cell surface.

  7. Serological testing reveals a patient has IgG antibodies to hepatitis B surface antigen (anti-HBs) but no HBsAg and no anti-HBc. This pattern most likely indicates:

    Answer: Successful vaccination against hepatitis B

    Anti-HBs alone (without anti-HBc) indicates immunity from vaccination, since the vaccine contains only HBsAg and does not induce core antibodies.