Question 1

A patient presents with a rapidly spreading, painful infection of the deep dermis and subcutaneous fat, accompanied by redness, swelling, and warmth. The causative agent is most likely Streptococcus pyogenes or Staphylococcus aureus. What is the most appropriate initial treatment for this condition?

Accepted Answer

Oral or intravenous antibiotics

Question 2

Which of the following best explains why Streptococcus pyogenes can cause both pharyngitis and acute glomerulonephritis?

Accepted Answer

It triggers immune-mediated inflammation due to molecular mimicry.

Question 3

A child develops a 'slapped cheek' rash and mild joint pain. Which viral agent is most likely responsible for these symptoms?

Accepted Answer

Parvovirus B19

Question 4

A burn patient develops a blue-green pus at the wound site and fever. Which microbial agent is most likely responsible, and what is a key diagnostic clue?

Accepted Answer

Pseudomonas aeruginosa; pigment (pyocyanin) in exudate

Question 5

A patient presents with a black, painless ulcer after contact with infected animals. Which disease is this, and what is the causative agent?

Accepted Answer

Cutaneous anthrax; Bacillus anthracis

Question 6

Which of the following is a distinguishing feature of botulism compared to tetanus?

Accepted Answer

Botulism toxin blocks acetylcholine release; tetanus toxin blocks inhibitory neurotransmitter release.

Question 7

A patient with a history of tick exposure develops a bull's-eye rash, fever, and joint pain. Which disease is most likely, and what is the causative agent?

Accepted Answer

Lyme disease; Borrelia burgdorferi

Question 8

Which of the following best describes the pathogenesis of rheumatic fever following a Streptococcus pyogenes pharyngitis?

Accepted Answer

Immune response cross-reacts with heart tissue antigens

Question 9

A patient presents with fever, headache, and a stiff neck. Cerebrospinal fluid analysis reveals increased WBCs and decreased glucose. Which of the following is the most likely diagnosis?

Accepted Answer

Bacterial meningitis

Question 10

Which of the following is a key reason why Neisseria meningitidis can cause epidemics in dormitories and barracks?

Accepted Answer

It spreads via respiratory droplets in close-contact settings.

Question 11

A patient develops a painless genital ulcer (chancre) that heals spontaneously, followed weeks later by a widespread rash. Which disease is this, and what is the causative agent?

Accepted Answer

Syphilis; Treponema pallidum

Question 12

Which of the following is the most common cause of bacterial urinary tract infections (UTIs)?

Accepted Answer

Escherichia coli

Question 13

A patient presents with severe, watery diarrhea after recent antibiotic use. Stool analysis reveals the presence of toxin-producing Clostridium difficile. What is the most important initial step in management?

Accepted Answer

Discontinue the inciting antibiotic

Question 14

Which of the following diseases is caused by a prion and is characterized by rapidly progressive dementia and death within 12 months?

Accepted Answer

Variant Creutzfeldt–Jakob Disease (vCJD)

Question 15

A patient develops a painless, slow-growing tumor-like lesion on the foot after a thorn injury while gardening. The lesion is firm and ulcerates. Which fungal disease is most likely?

Accepted Answer

Mycetoma

Question 16

A newborn develops severe conjunctivitis and corneal inflammation shortly after birth. The mother had untreated Neisseria gonorrhoeae. What is the best preventive measure for this condition?

Accepted Answer

Prophylactic antibiotic eye drops at birth

Question 17

Which of the following is a key feature of dengue hemorrhagic fever that distinguishes it from classic dengue fever?

Accepted Answer

Hemorrhage and plasma leakage due to immune response

Question 18

A patient presents with a painless, slow-growing ulcer on the skin that spreads along lymphatic channels after a thorn prick. Which organism is most likely responsible?

Accepted Answer

Sporothrix schenckii

Question 19

Which of the following best explains why the influenza virus requires annual vaccination?

Accepted Answer

It undergoes frequent antigenic drift and shift.

Question 20

A patient with HIV/AIDS develops difficulty breathing, fever, and hypoxia. Sputum analysis reveals Pneumocystis jirovecii. What is the most appropriate treatment?

Accepted Answer

Trimethoprim-sulfamethoxazole

Microbial Diseases of Organ Systems: Skin, Nervous, Cardiovascular, Respiratory, Digestive, Urinary & Reproductive Systems

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