Question 1

Which of MELTING the following statements best explains why the central nervous system (CNS) is less frequently infected than the peripheral nervous system (PNS)?

Accepted Answer

The CNS is protected by the blood-brain barrier and encased by bone, making it difficult for pathogens and antibiotics to cross.

Question 2

A patient presents with a sudden onset of severe headache, fever, neck stiffness, and confusion. A lumbar puncture reveals cloudy cerebrospinal fluid with a high neutrophil count. Which of the following is the most likely causative agent?

Accepted Answer

Streptococcus pneumoniae

Question 3

Which of the following best describes the pathogenesis of botulism?

Accepted Answer

Clostridium botulinum produces an AB toxin that blocks the release of neurotransmitter at neuromuscular junctions, resulting in flaccid paralysis.

Question 4

A 3-month-old infant develops fever, irritability, poor feeding, and bulging fontanels. Which of the following is the most common cause of neonatal meningitis?

Accepted Answer

Streptococcus agalactiae (Group B Streptococcus)

Question 5

Which of the following statements about the blood-brain barrier is correct?

Accepted Answer

It is composed of special cells lining CNS capillaries, making it difficult for both pathogens and antibiotics to cross.

Question 6

A college student living in a crowded dormitory develops fever, headache, stiff neck, and a purplish rash. Which organism is most likely responsible, and what is a key virulence factor?

Accepted Answer

Neisseria meningitidis; capsule and endotoxin production

Question 7

Which of the following best explains why Haemophilus influenzae type b (Hib) vaccine is less effective in children under 2 years old?

Accepted Answer

Polysaccharide antigens are T-cell independent and do not elicit a strong immune response in young children.

Question 8

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

Accepted Answer

The presence of petechiae (purplish skin spots) due to capillary damage.

Question 9

A patient with a history of eating unpasteurized soft cheese develops fever, muscle aches, and later, meningitis. Which organism is most likely responsible, and what is a key feature of its epidemiology?

Accepted Answer

Listeria monocytogenes; can grow at refrigeration temperatures

Question 10

Which of the following best describes the pathogenesis of prion diseases such as Creutzfeldt-Jakob disease (CJD)?

Accepted Answer

Misfolded prion proteins induce misfolding of normal proteins, leading to neuronal death and spongiform changes in brain tissue.

Question 11

A patient presents with gradual loss of sensation and pigmentation changes in the skin, followed by muscle wasting and deformities of the face. Which organism is most likely responsible?

Accepted Answer

Mycobacterium leprae

Question 12

Which of the following is the main route of transmission for poliovirus in endemic areas?

Accepted Answer

Fecal-oral route due to poor sanitation

Question 13

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

Accepted Answer

The inflammatory response in viral meningitis involves fewer cells entering the cerebrospinal fluid.

Question 14

A patient develops fever, headache, vomiting, and later, disorientation and seizures after being bitten by a mosquito. Which of the following is the most likely diagnosis?

Accepted Answer

Viral encephalitis caused by an arbovirus

Question 15

Which of the following is a key reason why prion diseases are difficult to control in healthcare settings?

Accepted Answer

Prions are highly resistant to standard disinfectants, heat, and radiation.

Question 16

A patient presents with fever, agitation, hallucinations, and difficulty swallowing after being bitten by a wild animal. Which of the following is the most appropriate immediate intervention?

Accepted Answer

Thoroughly wash the wound, administer anti-rabies antibody, and begin post-exposure vaccination.

Question 17

Which of the following best explains why the oral Sabin polio vaccine is still used in some countries despite the risk of vaccine-derived paralytic polio?

Accepted Answer

It provides better herd immunity and is more effective at interrupting person-to-person transmission.

Question 18

A patient develops rapidly progressive neurological symptoms after swimming in warm freshwater. Which organism is most likely responsible, and what is the prognosis?

Accepted Answer

Naegleria fowleri; almost always fatal

Question 19

Which of the following best describes the epidemiology of African sleeping sickness caused by Trypanosoma brucei gambiense?

Accepted Answer

Humans are the main reservoir, and transmission is mainly human-to-human via tsetse flies.

Microbiology Chapter 26: Infections of the Nervous System – Structure, Function, and Major Pathogens

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