Question 1

Which of the following best explains why the central nervous system (CNS) is considered an axenic environment?

Accepted Answer

It is protected by the blood-brain barrier, which prevents most pathogens and large molecules from entering.

Question 2

A patient presents with a stiff neck, severe headache, and fever. A lumbar puncture reveals cloudy cerebrospinal fluid (CSF) with increased white blood cells and decreased glucose. Which diagnosis is most likely?

Accepted Answer

Bacterial meningitis

Question 3

Which virulence factor of Neisseria meningitidis is primarily responsible for its ability to evade phagocytosis and persist in the bloodstream?

Accepted Answer

Polysaccharide capsule

Question 4

A child develops a vesicular rash on the trunk and limbs two weeks after a mild fever. The lesions progress from macules to papules to fluid-filled vesicles. Which virus is most likely responsible?

Accepted Answer

Varicella-zoster virus (VZV)

Question 5

Which of the following statements about shingles is CORRECT?

Accepted Answer

It results from reactivation of latent VZV in nerve ganglia.

Question 6

Why is active immunization effective as post-exposure prophylaxis (PEP) for rabies?

Accepted Answer

Rabies virus replicates slowly in muscle cells before entering the CNS, allowing time for the immune response to develop.

Question 7

Which of the following best describes the pathogenesis of poliomyelitis leading to paralysis?

Accepted Answer

Poliovirus destroys motor neurons in the spinal cord, resulting in flaccid paralysis.

Question 8

A 60-year-old patient with a history of chickenpox develops a painful, localized rash that does not cross the midline. What is the most likely explanation?

Accepted Answer

Reactivation of latent VZV in a nerve ganglion

Question 9

Which of the following is a distinguishing feature of meningococcal meningitis compared to other types of bacterial meningitis?

Accepted Answer

Presence of a petechial rash due to LOS-induced tissue damage

Question 10

Which of the following best explains why viral meningitis is generally less severe than bacterial meningitis?

Accepted Answer

Viruses cause less tissue damage and inflammation in the meninges compared to bacteria.

Question 11

A patient is diagnosed with bacterial meningitis caused by Streptococcus pneumoniae. Which virulence factor allows this bacterium to cross the blood-brain barrier?

Accepted Answer

Phosphorylcholine in the cell wall

Question 12

Which of the following is the most effective strategy for preventing poliomyelitis in a population?

Accepted Answer

Global vaccination with oral or inactivated polio vaccines

Question 13

Which of the following equations best represents the probability $$P of a $$person developing shingles if they had chickenpox as a child, given that 15-20% of such individuals develop shingles?

Accepted Answer

$$P = 0.15$$ 	ext{ to } 0.20$

Question 14

Which of the following is a key reason why viruses can cross the blood-brain barrier more easily than bacteria?

Accepted Answer

Viruses are smaller and can pass through tight junctions between endothelial cells.

Question 15

A patient bitten by a potentially rabid animal receives post-exposure prophylaxis (PEP) with both rabies vaccine and human rabies immunoglobulin. What is the rationale for this combined approach?

Accepted Answer

Immunoglobulin provides immediate passive immunity, while the vaccine induces active immunity over time.

Question 16

Which of the following best describes the epidemiology of chickenpox and shingles?

Accepted Answer

A person with shingles can transmit VZV to someone who has never had chickenpox, causing chickenpox in the recipient.

Question 17

Which of the following is a hallmark symptom of rabies during the CNS stage?

Accepted Answer

Hydrophobia (fear of water)

Question 18

A lumbar puncture is performed on a patient with suspected meningitis. Which laboratory findings are most consistent with bacterial (not viral) meningitis?

Accepted Answer

Cloudy CSF, decreased glucose, increased white blood cell count

Question 19

Which of the following best explains why post-polio syndrome occurs decades after the initial poliovirus infection?

Accepted Answer

Degeneration of nerves that were damaged during the original infection

Microbial Diseases of the Nervous System: Meningitis, Chickenpox/Shingles, Rabies, and Poliomyelitis

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