Question 1

A 7-year-old child presents with fever, headache, and a stiff neck, followed by nausea and vomiting. A gram-negative, aerobic diplococcus with a capsule is isolated from the cerebrospinal fluid. Which of the following is the most likely causative agent?

Accepted Answer

Neisseria meningitidis

Question 2

A patient develops a rapidly progressing, fatal encephalitis after swimming in a warm freshwater lake. The causative organism enters through the nasal mucosa and feeds on brain tissue. Which microbe is responsible?

Accepted Answer

Naegleria fowleri

Question 3

Which of the following best explains why broad-spectrum, third-generation cephalosporins are used as initial treatment for suspected bacterial meningitis?

Accepted Answer

They can cross the blood-brain barrier and cover a wide range of likely pathogens.

Question 4

A college student living in a crowded dormitory develops a non-fading rash, fever, and neck stiffness. Which feature of the causative agent is most important for its pathogenicity?

Accepted Answer

Presence of a polysaccharide capsule

Question 5

A soil fungus associated with pigeon droppings is inhaled and can cause meningitis in immunocompromised patients. Which organism is this, and what is its primary route of transmission?

Accepted Answer

Cryptococcus neoformans; respiratory route

Question 6

A patient bitten by a wild animal develops hydrophobia and muscle spasms. The causative agent is a bullet-shaped RNA virus. Which of the following best describes the pathogenesis of this disease?

Accepted Answer

The virus multiplies in skeletal muscle and travels through the peripheral nervous system to the brain.

Question 7

A 5-year-old child develops a rapidly progressing fever, sore throat, and an enlarged spleen. Laboratory tests reveal the presence of atypical lymphocytes. Which virus is most likely responsible, and what is a serious cancer associated with it in Africa?

Accepted Answer

Epstein-Barr virus; Burkitt's lymphoma

Question 8

A patient presents with a painless ulcer on the hand after handling animal hides, followed by severe respiratory distress. The causative agent is a gram-positive, endospore-forming rod. Which disease is this, and what is the most fatal form?

Accepted Answer

Anthrax; inhalational (pulmonary) anthrax

Question 9

A patient develops intense, swollen lymph nodes (buboes) and a high fever after being bitten by a flea. The disease progresses to pneumonia with nearly 100% mortality if untreated. Which organism is responsible, and what is the most dangerous form of the disease?

Accepted Answer

Yersinia pestis; pneumonic plague

Question 10

A patient with a history of tick exposure develops a measles-like rash on the palms and soles, along with fever and headache. Which organism is most likely responsible?

Accepted Answer

Rickettsia rickettsii

Question 11

A patient with gram-negative sepsis is treated with antibiotics and develops a sudden, severe drop in blood pressure. Which of the following best explains this phenomenon?

Accepted Answer

Antibiotics cause the release of endotoxins (LPS) from dying bacteria.

Question 12

A patient presents with a chronic cough and weight loss. Acid-fast rods are seen in a sputum sample. Which feature of the causative agent contributes most to its resistance to drying and many antimicrobials?

Accepted Answer

High lipid content in the cell wall

Question 13

A hospital outbreak of pneumonia is traced to a cooling tower. The causative agent is a gram-negative rod that grows in water systems and is transmitted by inhaling aerosols. Which organism is responsible?

Accepted Answer

Legionella pneumophila

Question 14

Which of the following mechanisms is NOT a normal protection of the lower respiratory tract?

Accepted Answer

Production of erythrogenic toxin

Question 15

The influenza virus is capable of causing pandemics due to major changes in its genome. Which process is responsible for these major changes, and what is the result?

Accepted Answer

Antigenic shift; population has little to no immunity to the new strain

Question 16

A patient with strep throat develops a red rash and a high fever. Which toxin is responsible for the rash, and which organism produces it?

Accepted Answer

Erythrogenic toxin; Streptococcus pyogenes

Question 17

A patient develops recurring bouts of high fever and jaundice after being bitten by a soft tick. Which organism is most likely responsible for this relapsing fever?

Accepted Answer

Borrelia spp.

Question 18

A young adult develops a mild respiratory illness. The causative agent is transmitted person-to-person and is common in young people. Which organism is most likely responsible?

Accepted Answer

Chlamydophila pneumoniae

Question 19

A patient with a history of consuming unpasteurized milk develops Q fever. Which organism is responsible, and what is the primary mode of transmission?

Accepted Answer

Coxiella burnetii; inhalation of aerosols from farm animals

Question 20

A patient with leprosy presents with disfiguring nodules and loss of sensation in the skin. Which organism is responsible, and what is a key feature of its pathogenesis?

Accepted Answer

Mycobacterium leprae; growth in peripheral nerves and skin cells

Question 21

A laboratory technician is culturing a respiratory pathogen that forms 'fried-egg' colonies and lacks a cell wall. Which organism is this, and what disease does it cause?

Accepted Answer

Mycoplasma pneumoniae; walking pneumonia

Microbial Diseases of the Nervous, Cardiovascular, Lymphatic, and Respiratory Systems

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