Question 1

Which of the following best explains why spirochetes such as Treponema pallidum are able to penetrate host tissues so effectively?

Accepted Answer

They move in a corkscrew fashion due to the rotation of axial filaments.

Question 2

A patient presents with a painless genital ulcer, followed weeks later by a widespread rash and then neurological symptoms years later. Which pathogen is most likely responsible for this progression?

Accepted Answer

Treponema pallidum pallidum

Question 3

Which phase of syphilis is most difficult to diagnose and treat, and why?

Accepted Answer

Tertiary syphilis, because the bacteria are rarely detected and penicillin is ineffective.

Question 4

A child living in an impoverished area develops skin lesions after contact with another child’s sores. Which organism is most likely responsible?

Accepted Answer

Treponema pallidum pertenue

Question 5

A veterinarian develops fever, muscle pain, and jaundice after cleaning animal cages. Which organism is most likely responsible, and what is the most effective treatment?

Accepted Answer

Leptospira interrogans; intravenous penicillin

Question 6

A patient presents with recurring episodes of fever and septicemia after a louse bite. Which mechanism allows the causative agent to evade the immune system?

Accepted Answer

Antigenic variation

Question 7

Which of the following best describes the transmission and prevention of Lyme disease?

Accepted Answer

Transmitted by hard ticks; prevented by avoiding tick-infested areas

Question 8

A patient develops severe diarrhea with 'rice-water stool' after drinking untreated water. Which bacterial toxin is responsible, and what is the primary treatment?

Accepted Answer

Cholera toxin; fluid and electrolyte replacement

Question 9

Which of the following equations best represents the mechanism by which cholera toxin causes fluid loss in the intestines?

Accepted Answer

$$\mathrm{Cholera\ toxin} \rightarrow \mathrm{Adenylate\ cyclase\ activation} \rightarrow \uparrow [cAMP] \rightarrow \uparrow \mathrm{Cl^-}, \mathrm{Na^+}, \mathrm{H_2O}\ \mathrm{secretion}$$

Question 10

A patient with a history of eating undercooked poultry develops bloody diarrhea. Which organism is most likely responsible, and what is the best prevention strategy?

Accepted Answer

Campylobacter jejuni; proper food handling and preparation

Question 11

Which of the following is a key virulence factor of Helicobacter pylori that allows it to survive in the acidic environment of the stomach?

Accepted Answer

Production of urease to neutralize stomach acid

Question 12

A patient is diagnosed with peptic ulcers and tests positive for urease activity in the stomach. Which treatment regimen is most appropriate?

Accepted Answer

Antimicrobials and acid-inhibiting drugs

Question 13

Which of the following best describes the transmission and prevention of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever?

Accepted Answer

Transmitted by hard ticks; prevented by avoiding tick bites

Question 14

A patient presents with high fever, depression, and a rash after living in crowded, unsanitary conditions. Which organism is most likely responsible?

Accepted Answer

Rickettsia prowazekii

Question 15

Which of the following best describes the developmental cycle of Chlamydia trachomatis?

Accepted Answer

Alternates between infectious elementary bodies and replicative reticulate bodies within host cells

Question 16

A sexually active patient presents with genital lesions and swollen lymph nodes (buboes). Which organism is most likely responsible, and what is the best prevention strategy?

Accepted Answer

Chlamydia trachomatis; abstinence and prompt antibacterial treatment

Question 17

Which of the following best explains why Mycoplasma pneumoniae is difficult to diagnose in the laboratory?

Accepted Answer

It lacks a cell wall and grows slowly in culture.

Question 18

A 10-year-old child develops a persistent dry cough and mild pneumonia after exposure to classmates. Which organism is most likely responsible, and what is the best treatment?

Accepted Answer

Mycoplasma pneumoniae; macrolides or doxycycline

Question 19

Which of the following equations best represents the relationship between the number of cases of Lyme disease and time, as shown in epidemiological data?

Accepted Answer

$$\mathrm{Cases\ of\ Lyme\ disease} \propto \mathrm{Time}$$

Miscellaneous Bacterial Agents of Disease: Spirochetes, Vibrios, Rickettsias, Chlamydias, and Mycoplasmas

Study Guide - Practice Questions

Study Guide - Flashcards