FPGEE Microbiology and Immunology Flashcards

Which of the following best describes herd immunity?

Answer: A sufficient proportion of a population is immune, reducing pathogen spread to unvaccinated individuals

Herd immunity occurs when enough individuals are immune (through vaccination or prior infection) that transmission chains are broken, protecting even unimmunized members.

Neisseria gonorrhoeae is resistant to penicillin mainly because of:

Answer: Altered PBPs and beta-lactamase production

Gonococci resist penicillin through both plasmid-encoded beta-lactamase (penicillinase) and chromosomal mutations altering PBPs and porins.

The live attenuated varicella (chickenpox) vaccine is a contraindication in pregnancy primarily because:

Answer: Live vaccine virus may cross the placenta and infect the fetus

Live attenuated viruses carry a theoretical risk of transplacental transmission and fetal infection, so varicella vaccine is contraindicated during pregnancy.

Which innate immune cell is the primary phagocyte responsible for clearing bacterial infections in the bloodstream?

Answer: Neutrophils

Neutrophils (PMNs) are the first-responder phagocytes of innate immunity, rapidly migrating to sites of infection and engulfing bacteria.

Which antiviral agent inhibits the neuraminidase enzyme of influenza A and B viruses?

Answer: Oseltamivir

Oseltamivir (Tamiflu) and zanamivir are neuraminidase inhibitors that prevent new viral particles from being released from infected cells.

The Mantoux tuberculin skin test (TST) detects prior exposure to Mycobacterium tuberculosis by measuring which immune response?

Answer: Type IV delayed-type hypersensitivity (DTH)

The TST measures a Type IV (cell-mediated, delayed-type) hypersensitivity reaction in which sensitized T cells respond to purified protein derivative (PPD) 48–72 hours after injection.