Which of the following is not caused by Rickettsia?

The choice highlighting typhoid fever as not caused by Rickettsia is accurate because typhoid fever is caused by the bacterium Salmonella enterica serotype Typhi (S. Typhi). This disease is primarily transmitted through contaminated food and water, leading to systemic illness characterized by high fever, abdominal pain, and intestinal issues.

In contrast, the other options—typhus, Q fever, and Rocky Mountain spotted fever—are indeed diseases caused by Rickettsia species. Typhus is linked to Rickettsia prowazekii or Rickettsia typhi, and is transmitted by lice and fleas. Q fever is caused by Coxiella burnetii, which is often mistakenly associated with Rickettsia due to similarities in transmission and presentation but is not a Rickettsia species. Rocky Mountain spotted fever is caused by Rickettsia rickettsii, transmitted by tick bites and characterized by fever, rash, and potential complications if left untreated.

Recognizing the specific pathogens responsible for different diseases is crucial in microbiology and infectious disease management.