Question 1

Which of the following best explains why Treponema pallidum pallidum (the causative agent of syphilis) cannot be transmitted by inanimate objects?

Accepted Answer

It is rapidly killed outside the human body due to its specific growth requirements.

Question 2

A patient presents with a painless ulcer on the genitals, followed by a widespread rash on the palms and soles. Which pathogen is most likely responsible for these symptoms?

Accepted Answer

Treponema pallidum pallidum

Question 3

Which phase of untreated syphilis is characterized by the appearance of gummas and neurological symptoms?

Accepted Answer

Tertiary phase

Question 4

A child living in an impoverished area develops skin lesions after contact with another child’s sores. Which Treponema species is most likely responsible for this nonvenereal infection?

Accepted Answer

Treponema pallidum endemicum

Question 5

Which of the following is the primary vector for Borrelia burgdorferi, the causative agent of Lyme disease?

Accepted Answer

Ixodes tick

Question 6

A patient develops an expanding red 'bull’s-eye' rash, followed by neurological symptoms and arthritis. Which disease is most consistent with this progression?

Accepted Answer

Lyme disease

Question 7

Which of the following best describes the mechanism of action of cholera toxin?

Accepted Answer

It activates adenylate cyclase, increasing cAMP and causing secretion of electrolytes and water.

Question 8

A person develops severe watery diarrhea described as 'rice-water stool' after drinking contaminated water. Which organism is most likely responsible?

Accepted Answer

Vibrio cholerae

Question 9

Which of the following is the most effective initial treatment for cholera?

Accepted Answer

Fluid and electrolyte replacement

Question 10

A veterinarian is exposed to animal urine and develops fever, hemorrhaging, and kidney dysfunction. Which organism is most likely responsible?

Accepted Answer

Leptospira interrogans

Question 11

Which of the following is a distinguishing feature of Vibrio species compared to enteric bacteria?

Accepted Answer

Polar flagella

Question 12

A patient presents with relapsing episodes of fever and septicemia after traveling to Africa. Spirochetes are observed in the blood. Which is the most likely diagnosis?

Accepted Answer

Relapsing fever

Question 13

Which of the following best explains why tertiary syphilis is difficult to treat with penicillin?

Accepted Answer

The symptoms are primarily due to the immune response, not active infection.

Question 14

Which of the following is the most common source of Campylobacter jejuni infection in the United States?

Accepted Answer

Poultry

Question 15

A patient with a history of peptic ulcers is found to have a slightly helical, motile bacterium colonizing the stomach. Which virulence factor helps this bacterium survive in the acidic environment?

Accepted Answer

Urease

Question 16

Which of the following is the best method to prevent Lyme disease in endemic areas?

Accepted Answer

Avoidance of ticks and use of repellents

Question 17

Which of the following equations best represents the mechanism by which cholera toxin leads to diarrhea?

Accepted Answer

$$\mathrm{Cholera\ toxin} \rightarrow \mathrm{AC} \rightarrow \uparrow cAMP \rightarrow \uparrow \mathrm{Cl^-}, \mathrm{Na^+}, \mathrm{H_2O}$$

Question 18

Which of the following is a key reason why eradication of Leptospira interrogans is impractical?

Accepted Answer

There are numerous wild and domestic animal reservoirs.

Question 19

A fisherman develops a rapidly progressing wound infection after washing a cut with seawater. Which Vibrio species is most likely responsible?

Accepted Answer

Vibrio vulnificus

Question 20

Which of the following laboratory tests would best confirm the presence of Helicobacter pylori in a patient with gastritis?

Accepted Answer

Positive urease test

Pathogenic Rickettsias, Chlamydias, Spirochetes, and Vibrios: Structure, Physiology, and Diseases

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