Question 1

Which of the following statements best explains why infections of the central nervous system (CNS) are rare but very serious?

Accepted Answer

The CNS is protected by the blood-brain barrier, which restricts entry of most pathogens and drugs.

Question 2

A patient presents with fever, headache, and stiff neck. A lumbar puncture is performed to obtain cerebrospinal fluid (CSF). Which of the following is the most immediate reason for this procedure?

Accepted Answer

To diagnose or rule out meningitis by analyzing the CSF.

Question 3

Which of the following organisms is most commonly associated with epidemics of meningitis in college dormitories and army barracks?

Accepted Answer

Neisseria meningitidis

Question 4

A child under 4 years old develops meningitis. Which organism is most likely responsible, and what is the best preventive measure?

Accepted Answer

Haemophilus influenzae type B; Hib vaccine

Question 5

Which of the following best describes the mechanism of action of tetanospasmin, the neurotoxin produced by Clostridium tetani?

Accepted Answer

It blocks the release of inhibitory neurotransmitters, causing muscle spasms.

Question 6

A family consumes home-canned vegetables and develops double vision, difficulty swallowing, and flaccid paralysis. Which organism is responsible, and what is the most effective immediate treatment?

Accepted Answer

Clostridium botulinum; administration of antitoxin

Question 7

Which of the following is a unique clinical sign of meningococcal meningitis that helps distinguish it from other forms?

Accepted Answer

A rash that does not fade when pressed

Question 8

A patient with AIDS develops fungal meningitis after exposure to dried bird droppings. Which organism is most likely responsible?

Accepted Answer

Cryptococcus neoformans

Question 9

Which of the following best explains why Streptococcus pneumoniae is a leading cause of bacterial meningitis despite being normal flora in the throat?

Accepted Answer

It has a capsule that prevents phagocytosis, allowing it to evade the immune system.

Question 10

A patient presents with discolored skin patches, loss of sensation, and thickened earlobes. Which disease is most likely, and what is the causative agent?

Accepted Answer

Leprosy; Mycobacterium leprae

Question 11

Which of the following best describes the pathogenesis of rabies virus after a bite from an infected animal?

Accepted Answer

The virus proliferates in muscle and connective tissue, then travels up peripheral nerves to the CNS.

Question 12

Which of the following is a key reason why improved sanitation paradoxically increased the severity of poliomyelitis outbreaks in the 20th century?

Accepted Answer

Children were exposed at an older age, after maternal antibodies had waned.

Question 13

A patient develops fever, headache, vomiting, and abrupt onset of disorientation and seizures after a mosquito bite. Which type of virus is most likely responsible?

Accepted Answer

Arbovirus

Question 14

Which of the following best explains why prion diseases are difficult to control and can be transmitted by surgical instruments?

Accepted Answer

Prions are abnormally shaped proteins that are resistant to standard sterilization methods.

Question 15

Which of the following equations best represents the fatal dose of tetanospasmin for an average adult weighing 70 kg, given that the fatal dose is $$2.5 \ \mathrm{ng/kg}$$?

Accepted Answer

$$2.5 \ \mathrm{ng/kg} 	imes 70 \ \mathrm{kg} = 175 \ \mathrm{ng}$$

Question 16

Which of the following best describes the main difference between the effects of tetanus and botulism toxins?

Accepted Answer

Tetanus toxin causes spastic paralysis; botulism toxin causes flaccid paralysis.

Question 17

A newborn develops botulism after ingesting honey. Which of the following best explains why infants are particularly susceptible?

Accepted Answer

Infants have immature gut flora, allowing Clostridium botulinum spores to germinate and produce toxin.

Question 18

Which of the following is the most effective way to prevent Zika virus infection in endemic areas?

Accepted Answer

Reducing mosquito breeding sites

Question 19

Which of the following best explains why the blood-brain barrier makes treatment of CNS infections challenging?

Accepted Answer

Only lipid-soluble drugs or those with specific carrier proteins can cross the barrier.

Infections of the Nervous System: Microbiology Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards