American Board of Internal Medicine (ABIM) Certification Practice Exam

Which organism is responsible for causing Rocky Mountain spotted fever?

1. Borrelia burgdorferi

2. Rickettsia rickettsii

3. Clostridium botulinum

4. Leptospira interrogans

The correct answer is: Rickettsia rickettsii

Rocky Mountain spotted fever is caused by the organism Rickettsia rickettsii. This pathogen is a type of bacteria that belongs to the family Rickettsiaceae and is primarily transmitted to humans through the bite of infected ticks, particularly the American dog tick and the Rocky Mountain wood tick. Rickettsia rickettsii infects the endothelial cells of blood vessels, leading to the clinical manifestations associated with the disease, such as fever, rash, and potential severe complications if left untreated. Early recognition and treatment are crucial, as the disease can progress rapidly and may lead to serious complications. The other organisms listed do not cause Rocky Mountain spotted fever; for instance, Borrelia burgdorferi is responsible for Lyme disease, Clostridium botulinum is associated with botulism, and Leptospira interrogans causes leptospirosis. Understanding these distinctions is imperative for proper diagnosis and treatment of these different infectious diseases.