Question 1

Which structure in the lower respiratory system is primarily responsible for gas exchange, and what cellular defense mechanism operates there?

Accepted Answer

Alveoli; alveolar macrophages

Question 2

A patient presents with a sore throat, fever, and a tough grayish membrane in the throat. Which pathogen is most likely responsible, and what is the main virulence factor?

Accepted Answer

Corynebacterium diphtheriae; exotoxin

Question 3

Which of the following is a major reason why the lower respiratory system is nearly sterile?

Accepted Answer

Alveolar macrophages destroy microorganisms

Question 4

A child with a bulging eardrum and pus formation is diagnosed with otitis media. Which organism is LEAST likely to be the cause?

Accepted Answer

Mycobacterium tuberculosis

Question 5

Which bacterial species is resistant to phagocytosis and produces streptokinases and streptolysins, causing local inflammation and fever?

Accepted Answer

Streptococcus pyogenes

Question 6

Which disease is characterized by three stages: catarrhal, paroxysmal, and convalescence, and is prevented by the DTaP vaccine?

Accepted Answer

Pertussis (Whooping Cough)

Question 7

During the pathogenesis of tuberculosis, what is the fate of tubercle bacilli if host defenses are inadequate?

Accepted Answer

They are released into the lungs and cardiovascular system

Question 8

Which diagnostic test for tuberculosis relies on T cell reaction to purified protein derivative and results in delayed hypersensitivity?

Accepted Answer

Tuberculin skin test (Mantoux test)

Question 9

A patient with pneumonia is found to have Gram-positive, encapsulated diplococci in their sputum. Which test would confirm the diagnosis?

Accepted Answer

Optochin-inhibition test

Question 10

Which organism causes primary atypical pneumonia, lacks a cell wall, and is diagnosed by PCR?

Accepted Answer

Mycoplasma pneumoniae

Question 11

Legionella pneumophila is most commonly transmitted to humans by which route?

Accepted Answer

Inhalation of aerosols from water sources

Question 12

Which respiratory disease is associated with bird droppings and is caused by an obligate intracellular bacterium?

Accepted Answer

Psittacosis (Ornithosis)

Question 13

Which of the following statements about COVID-19 is TRUE?

Accepted Answer

It is primarily transmitted by airborne droplets and aerosols

Question 14

Which viral respiratory disease is most common in infants and can cause life-threatening pneumonia, diagnosed by serological tests?

Accepted Answer

Respiratory Syncytial Virus (RSV)

Question 15

Which influenza virus feature allows it to evade host immunity through minor antigenic changes?

Accepted Answer

Antigenic drift

Question 16

A patient with AIDS develops pneumonia caused by a yeast-like fungus found in the alveoli. Which organism is most likely responsible?

Accepted Answer

Pneumocystis jirovecii

Question 17

Which equation best describes the rate of bacterial growth in tuberculosis, given a generation time of 20 hours?

Accepted Answer

$$N = N_0$ 	imes 2$$^{t/20}$$

Question 18

Which fungal disease is acquired from airborne conidia in areas with bird or bat droppings and is treated with itraconazole?

Accepted Answer

Histoplasmosis

Question 19

Which of the following is a primary indicator of AIDS and is 100% fatal if not treated?

Accepted Answer

Pneumocystis pneumonia (PCP)

Question 20

Which historical event involved the use of plague-ridden bodies as biological weapons, leading to the spread of the Black Death?

Accepted Answer

Siege of Kaffa (Ukraine), 1346

Microbial Diseases of the Respiratory System: Structure, Pathogenesis, and Clinical Features

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