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Rickettsia is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long).
Rickettsia rickettsii is a Gram-negative, intracellular, cocco-bacillus bacterium that was first discovered in 1902. [1] Having a reduced genome, the bacterium harvests nutrients from its host cell to carry out respiration, making it an organo-heterotroph.
They are obligate intracellular parasites, and some are notable pathogens, including Rickettsia, which causes a variety of diseases in humans, and Ehrlichia, which causes diseases in livestock. Another genus of well-known Rickettsiales is the Wolbachia , which infect about two-thirds of all arthropods and nearly all filarial nematodes. [ 2 ]
The Rickettsiaceae are a family of bacteria. The genus Rickettsia is the most prominent genus within the family. The bacteria that eventually formed the mitochondrion (an organelle in eukaryotic cells) is believed to have originated from this family. Most human pathogens in this family are in genus Rickettsia.
These bacteria are typically transmitted to humans through the bites of infected arthropods, such as ticks, fleas, and lice. Rickettsial diseases are characterized by a range of symptoms, which can vary depending on the specific type of rickettsial infection but often include fever, headache, rash, and muscle aches.
Bartonella quintana, originally known as Rochalimaea quintana, [2] and "Rickettsia quintana", [3] is a bacterium transmitted by the human body louse that causes trench fever. [4] This bacterial species caused outbreaks of trench fever affecting 1 million soldiers in Europe during World War I .
Rickettsia prowazekii is a species of gram-negative, obligate intracellular parasitic, aerobic bacilliform bacteria of class Alphaproteobacteria that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the main reservoir for R. prowazekii is the flying squirrel.
Rickettsia helvetica Beati, Peter, Burgdorfer, Aeschlirnami & Raoult, 1993 [ 1 ] [ 3 ] [ 4 ] [ 5 ] First recognized in 1979 in Ixodes ricinus ticks in Switzerland (hence the designation helvetica ) as a new member of the spotted fever group of Rickettsia , the R. helvetica bacterium was eventually isolated in 1993. [ 6 ]