What is the causative organism of Lyme disease?

Lyme disease is primarily caused by the bacterium Borrelia burgdorferi. This spirochete is transmitted to humans through the bite of infected black-legged ticks, commonly known as deer ticks. The disease was first identified in the 1970s in Lyme, Connecticut, and has since been recognized in various parts of the world where the ticks are prevalent.

This organism is distinct for its ability to evade the host's immune system and persist in the body, leading to chronic symptoms if not treated in the early stages. The characteristic symptoms often include fever, headache, fatigue, and a unique skin rash called erythema migrans, commonly described as a "bull’s-eye" rash.

The other organisms listed are associated with different infectious diseases. Rickettsia rickettsii is responsible for Rocky Mountain spotted fever, while Francisella tularensis causes tularemia. Salmonella enterica is known for causing gastrointestinal infections, particularly food poisoning. Understanding the specific pathogens responsible for each illness is crucial for diagnosis and appropriate treatment.