Question 1

A 7-year-old child presents with a barking cough and stridor. Which infection is most likely responsible for these symptoms, and what is the typical age group affected?

Accepted Answer

Croup; children under 5 years old

Question 2

Which of the following best explains why smoking increases the risk of respiratory infections?

Accepted Answer

Smoking damages cilia, impairing mucociliary clearance and weakening immune defenses

Question 3

A patient presents with a thick gray membrane in the throat, sore throat, and fever. Which disease is most likely, and what is the causative agent?

Accepted Answer

Diphtheria; Corynebacterium diphtheriae

Question 4

Which of the following best describes the function of hemagglutinin (HA) and neuraminidase (NA) in the influenza virus lifecycle?

Accepted Answer

HA mediates viral attachment to host cells; NA assists in the release of new viral particles

Question 5

A 35-year-old HIV-positive patient develops pneumonia with ground-glass opacities on chest X-ray. Sputum analysis reveals a fungus that cannot be cultured on standard media. Which organism is most likely responsible?

Accepted Answer

Pneumocystis jirovecii

Question 6

A patient presents with honey-colored crusted lesions around the nose and mouth. Which disease is this, and what is a common causative agent?

Accepted Answer

Impetigo; Staphylococcus aureus

Question 7

Which of the following is the most common cause of infectious blindness worldwide, and what is the causative agent?

Accepted Answer

Trachoma; Chlamydia trachomatis

Question 8

A newborn develops conjunctivitis a few days after birth. Which two pathogens are most commonly responsible for neonatal eye infections?

Accepted Answer

Neisseria gonorrhoeae and Chlamydia trachomatis

Question 9

A 22-year-old woman presents with dysuria, urgency, and cloudy urine. Which bacterium is most commonly responsible for urinary tract infections in otherwise healthy women?

Accepted Answer

Escherichia coli

Question 10

A patient with a history of antibiotic use develops severe diarrhea and pseudomembranous colitis. Which organism is most likely responsible, and what is a key feature of this bacterium?

Accepted Answer

Clostridium difficile; Gram-positive, endospore-forming rod

Question 11

A 4-year-old child presents with fever, high-pitched cough, conjunctivitis, and a descending rash. Small white spots are seen on the buccal mucosa. What is the most likely diagnosis?

Accepted Answer

Measles (Rubeola)

Question 12

A 30-year-old man develops a rapidly growing jaw tumor. Biopsy reveals association with Epstein-Barr virus (EBV). What is the most likely diagnosis?

Accepted Answer

Burkitt’s lymphoma

Question 13

A patient presents with fever, headache, stiff neck, and photophobia. Cerebrospinal fluid (CSF) analysis shows high neutrophils, low glucose, and high protein. What is the most likely diagnosis?

Accepted Answer

Bacterial meningitis

Question 14

A 6-month-old infant is brought to the ER with flaccid paralysis. The parents report feeding the child honey. Which organism is most likely responsible, and what is the mechanism of disease?

Accepted Answer

Clostridium botulinum; blocks acetylcholine release at neuromuscular junctions

Question 15

A 25-year-old man develops a bullseye-shaped rash after a tick bite. Which disease is this, and what is the causative agent?

Accepted Answer

Lyme disease; Borrelia burgdorferi

Question 16

Which of the following best describes the order of blood flow through the heart and major vessels?

Accepted Answer

Right atrium $$\rightarrow$$ right ventricle $$\rightarrow$$ pulmonary arteries $$\rightarrow$$ lungs $$\rightarrow$$ pulmonary veins $$\rightarrow$$ left atrium $$\rightarrow$$ left ventricle $$\rightarrow$$ aorta $$\rightarrow$$ body

Question 17

A patient presents with severe muscle rigidity and spasms after a puncture wound. Which organism is responsible, and what is the mechanism of its toxin?

Accepted Answer

Clostridium tetani; blocks inhibitory neurotransmitters causing spastic paralysis

Question 18

A 5-year-old child presents with perianal itching, especially at night. Which organism is most likely responsible, and how is the diagnosis confirmed?

Accepted Answer

Enterobius vermicularis (pinworm); identification of eggs on perianal tape test

Question 19

Which of the following is a protozoan infection transmitted by mosquitoes and characterized by cycles of fever and chills?

Accepted Answer

Malaria; Plasmodium species

Question 20

A patient presents with a rapidly progressing, blue-green wound infection after a burn. Which organism is most likely responsible, and what pigment does it produce?

Accepted Answer

Pseudomonas aeruginosa; pyocyanin

MCB 2010 Final Exam Review: Infectious Diseases of Organ Systems

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