Rickettsia rickettsii | |
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Scientific classification ![]() | |
Domain: | Bacteria |
Phylum: | Pseudomonadota |
Class: | Alphaproteobacteria |
Order: | Rickettsiales |
Family: | Rickettsiaceae |
Genus: | Rickettsia |
Species group: | Spotted fever group |
Species: | R. rickettsii
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Binomial name | |
Rickettsia rickettsii Brumpt, 1922
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Rickettsia rickettsii is a Gram-negative, intracellular, coccobacillus 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 organoheterotroph. Maintenance of its genome is carried out through vertical gene transfer where specialization of the bacterium allows it to shuttle host sugars directly into its TCA cycle.[2]
Other characteristics of the bacteria include membrane proteins that are useful in the identification of R. rickettsii strains and useful in the targeting of antibiotics. A capsule encircling the bacterium allows for attachment to host cells and additionally acts as a defense mechanism for resisting phagocytosis. Varying strains of R. rickettsii have different genotypes and phenotypes that alter the pathogenicity, virulence, and appearance of the bacteria.[3][4][5]
R. rickettsii is the causative agent of Rocky Mountain Spotted Fever and is transferred to its host via a tick bite. It is one of the most pathogenic Rickettsia species[6] and affects a large majority of the Western Hemisphere, most commonly the Americas.[7] The pathogenic agent has been found on every continent, except Antarctica; however, Rocky Mountain Spotted Fever occurs mostly in North, Central, and South America.[7] This prevalence is due to R. rickettsi thriving in warm, damp environments.[8] These environments provide sufficient conditions for the amplification of the bacteria within a vertebrate host, such as a horse or dog. The bacteria are transmitted through the vector, a tick, to a vertebrate host where it can then be amplified and passed on to a person, resulting in the zoonotic disease.[9]
Headache, high fever, and spotted rash are some effects of the disease with more severe cases resulting in organ damage and coma.[10][11][12] Antibiotics, such as doxycycline, target the ribosome of R. rickettsii in order to inhibit protein synthesis of the bacteria, providing a form of treatment for the disease.[13]
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