Final answer:
Rocky Mountain Spotted Fever is caused by the bacterium Rickettsia rickettsii, which is conveyed to humans by the bite of infected ticks such as the American dog tick, Rocky Mountain wood tick, and the brown dog tick.
Step-by-step explanation:
The organism responsible for causing Rocky Mountain Spotted Fever (RMSF) is Rickettsia rickettsii, which is an obligate intracellular bacterium. This bacterium is transmitted to humans through the bite of infected hard-bodied ticks, such as the American dog tick (Dermacentor variabilis), Rocky Mountain wood tick (D. andersoni), and the brown dog tick (Rhipicephalus sanguineus). RMSF is known for causing a petechial rash that often starts at the hands and wrists before spreading to the trunk of the body. Special staining methods are required to see these bacteria under a microscope, as they infect the cells of their tick hosts.