MCQ Microbiology Answer 50

The correct answer is A.

Anthrax forms extremely stable spores and has, in fact, been encountered in very old (i.e., deep) dirt in Israeli and Arabian excavation sites. The causative organism, Bacillus anthracis, is found in many animal species, and humans can acquire the organism either through contact with the animals or from locally contaminated soil. The pustule described in the question stem is called a "malignant pustule" and may be accompanied by lymphadenopathy. Most cases remain localized, but death can occur as the result of complications such as bacteremia, meningitis, and pneumonia.

Borrelia burgdorferi (choice B) causes Lyme disease. In the first stage of this disease, there is a localized expanding erythematous rash rather than an eschar. Furthermore, Lyme disease occurs in the U.S., Europe, and Asia, corresponding to the distribution of Ixodid ticks, which spread the infection.

Francisella tularensis (choice C) causes tularemia. The organism can persist for weeks to months but does not form spores that could survive for hundreds or thousands of years. Also, most human cases occur in the endemic areas of the U.S.

Spirillium minus (choice D) is one of the causes of rat-bite fever. There is no indication the man was bitten by a rat.

Yersinia pestis (choice E) causes bubonic plague. This organism does not form stable spores that could survive for extended periods of time.

Category: Microbiology MCQs