Question 1

Which of the following best explains why Streptococcus pneumoniae is able to cause severe pneumonia despite the presence of phagocytic cells in the lungs?

Accepted Answer

It produces a capsule that resists phagocytosis.

Question 2

A 5-year-old child presents with a sore throat, fever, and a gray pseudomembrane in the throat. Which pathogen is most likely responsible, and what is the best prevention strategy?

Accepted Answer

Corynebacterium diphtheriae; DTaP vaccine

Question 3

Which of the following statements about the common cold is CORRECT?

Accepted Answer

It is most commonly caused by rhinoviruses, which thrive at temperatures slightly lower than body temperature.

Question 4

A patient with a history of HIV presents with pneumonia. Sputum analysis reveals Pneumocystis jirovecii. Why is this infection particularly concerning in this patient population?

Accepted Answer

It is 100% fatal if not treated in immunocompromised individuals.

Question 5

Which of the following is a distinguishing symptom of scarlet fever compared to streptococcal pharyngitis?

Accepted Answer

Strawberry tongue and a pinkish red skin rash

Question 6

A patient presents with a persistent cough, night sweats, and weight loss. Acid-fast bacilli are seen in a sputum sample. Which of the following best explains why Mycobacterium tuberculosis is difficult to eradicate?

Accepted Answer

It contains mycolic acid in its cell wall, making it resistant to many chemicals and drying.

Question 7

Which of the following best describes the pathogenesis of Legionella pneumophila in Legionnaire's disease?

Accepted Answer

It multiplies within macrophages and is often found in artificial water supplies.

Question 8

Which of the following is a key reason why the influenza vaccine must be reformulated every year?

Accepted Answer

Antigenic drift and shift cause frequent changes in viral surface proteins.

Question 9

A patient with a history of spelunking in the Midwest presents with mild respiratory symptoms. Which organism is most likely responsible, and what is a key feature of its transmission?

Accepted Answer

Histoplasma capsulatum; airborne conidia from soil contaminated with bat or bird droppings

Question 10

Which of the following best explains why Mycoplasma pneumoniae infections are often called 'walking pneumonia'?

Accepted Answer

Symptoms are generally mild and patients are often able to continue daily activities.

Question 11

A 3-year-old child presents with a sore throat, fever, and difficulty swallowing. The child is found to have a 'hot potato voice' and is drooling. Which of the following is the most likely diagnosis and causative agent?

Accepted Answer

Epiglottitis; Haemophilus influenzae type B

Question 12

Which of the following is a major complication of untreated Streptococcus pyogenes pharyngitis?

Accepted Answer

Rheumatic fever

Question 13

A patient presents with a high fever, chest pain, and rust-colored sputum. Which organism is most likely responsible, and what is a key virulence factor?

Accepted Answer

Streptococcus pneumoniae; capsule

Question 14

Which of the following best describes the Mantoux test for tuberculosis?

Accepted Answer

It detects a delayed-type hypersensitivity reaction to injected TB proteins.

Question 15

Which of the following is TRUE regarding the pathogenesis of Bordetella pertussis?

Accepted Answer

It destroys ciliated cells in the trachea, impairing mucous clearance.

Question 16

A patient presents with pneumonia after a recent hospital stay. Sputum is thick and described as 'currant jelly.' Which organism is most likely responsible?

Accepted Answer

Klebsiella pneumoniae

Question 17

Which of the following is a major reason why the BCG vaccine is not widely used in the United States?

Accepted Answer

It causes a positive tuberculin skin test, complicating diagnosis.

Question 18

Which of the following best describes the transmission and risk factors for Coccidioidomycosis (Valley Fever)?

Accepted Answer

Inhalation of spores from dry, alkaline soils in the southwestern U.S.

Question 19

Which of the following is a key feature of the influenza virus that allows it to attach to host cells?

Accepted Answer

Hemagglutinin (HA) spikes

Question 20

A 2-year-old child is hospitalized with severe wheezing and coughing lasting more than a week. There is no fever unless a bacterial infection is present. Which virus is most likely responsible?

Accepted Answer

Respiratory syncytial virus (RSV)

Microbial Diseases of the Respiratory System

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