Question 1

Which of the following best explains why infections that reach the cerebrospinal fluid (CSF) can rapidly affect the entire central nervous system (CNS)?

Accepted Answer

The CSF circulates around the brain and spinal cord, distributing pathogens widely.

Question 2

A patient presents with sudden onset of fever, severe headache, neck stiffness, and confusion. Which of the following findings in the cerebrospinal fluid (CSF) would most strongly suggest a diagnosis of bacterial meningitis?

Accepted Answer

Elevated white blood cell count and detection of encapsulated bacteria

Question 3

Which of the following best describes the mechanism by which botulinum toxin causes paralysis?

Accepted Answer

It prevents acetylcholine release at the neuromuscular junction, resulting in flaccid paralysis.

Question 4

A 7-month-old infant is brought to the emergency department with descending, symmetric flaccid paralysis. The parents report feeding the infant honey. Which of the following is the most likely cause?

Accepted Answer

Clostridium botulinum spores germinating in the infant's gut

Question 5

Which of the following is the primary reason that prion diseases, such as variant Creutzfeldt-Jakob disease (vCJD), are difficult to control using standard food processing and disinfection methods?

Accepted Answer

Prions are resistant to routine cooking and standard disinfection procedures.

Question 6

A patient develops lockjaw and painful muscle spasms after stepping on a rusty nail. Which of the following best explains the pathophysiology of this disease?

Accepted Answer

Tetanospasmin blocks inhibitory neurotransmitter release, causing sustained muscle contraction.

Question 7

Which of the following prevention strategies is most effective for primary amoebic meningoencephalitis (PAM) caused by Naegleria fowleri?

Accepted Answer

Preventing untreated freshwater from entering the nose

Question 8

Trypanosoma brucei, the causative agent of African sleeping sickness, is able to evade the host immune system primarily by which mechanism?

Accepted Answer

Frequently changing its surface antigens

Question 9

Which of the following best explains why repeated Chlamydia trachomatis infection of the conjunctiva can lead to blindness (trachoma)?

Accepted Answer

Repeated inflammation and scarring turn eyelashes inward, abrading the cornea.

Question 10

A 30-year-old man develops gradual headache and signs of meningitis after exposure to bird droppings. He is found to be HIV-positive. Which virulence factor of Cryptococcus neoformans most contributes to its ability to cause disease in this patient?

Accepted Answer

A polysaccharide capsule and melanin that help evade host defenses

Question 11

Which of the following best describes the main route of transmission for poliovirus?

Accepted Answer

Fecal-oral spread, often via contaminated water or hands

Question 12

A patient is bitten by a stray dog and seeks medical attention. Which of the following is the most important immediate action to prevent rabies infection?

Accepted Answer

Urgent wound cleansing and postexposure prophylaxis

Question 13

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

Accepted Answer

It is normally free of resident microbes.

Question 14

Which of the following is a key prevention strategy for bacterial meningitis caused by Neisseria meningitidis?

Accepted Answer

Vaccination and respiratory precautions

Question 15

A patient presents with progressive psychiatric and neurologic decline. Brain biopsy reveals spongiform changes. Which of the following is the most likely cause?

Accepted Answer

A misfolded prion protein inducing abnormal folding in normal proteins

Question 16

Which of the following best explains why vaccines are a major prevention tool for both tetanus and poliomyelitis?

Accepted Answer

Both diseases can be prevented by inducing immunity to their respective toxins or viruses.

Question 17

A patient develops fever, lymphadenopathy, and later, sleep disturbances and behavioral changes after traveling to rural Africa. Which of the following is the most likely mode of transmission for this disease?

Accepted Answer

Bite from a tsetse fly vector

Question 18

Which of the following best explains why the blood-brain barrier can be both protective and problematic in the context of CNS infections?

Accepted Answer

It restricts entry of pathogens and many medicines, making treatment difficult.

Question 19

Which of the following best describes the difference in paralysis caused by botulism and tetanus?

Accepted Answer

Botulism causes descending flaccid paralysis; tetanus causes rigid, spasming muscles.

Question 20

A child in an endemic region develops repeated conjunctival infections, leading to eyelid scarring and corneal injury. Which of the following public health strategies is most effective in preventing this disease?

Accepted Answer

The SAFE strategy: Surgery, Antibiotics, Facial cleanliness, Environmental improvement

Microbial Diseases of the Nervous System and Eyes: Study Guide

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