Rickettsia conorii explained

Rickettsia conorii is a Gram-negative, obligate intracellular bacterium of the genus Rickettsia that causes human disease called boutonneuse fever, Mediterranean spotted fever, Israeli tick typhus, Astrakhan spotted fever, Kenya tick typhus, Indian tick typhus, or other names that designate the locality of occurrence while having distinct clinical features.^{[1] [2]} It is a member of the spotted fever group and the most geographically dispersed species in the group, recognized in most of the regions bordering on the Mediterranean Sea and Black Sea, Israel, Kenya, and other parts of North, Central, and South Africa, and India.^[1] The prevailing vector is the brown dog tick, Rhipicephalus sanguineus. The bacterium was isolated by Emile Brumpt in 1932^[3] and named after A. Conor, who in collaboration with A. Bruch, provided the first description of boutonneuse fever in Tunisia in 1910.^[4]

The genome of the bacterium has been sequenced and four subspecies have been identified.^{[5] [6] [7] [8] [9]}

Genomes of intracellular or parasitic bacteria undergo massive reduction compared to their free-living relatives. Examples include Rickettsia for alpha proteobacteria, T. whipplei for Actinobacteria, Mycoplasma for Firmicutes (the low G+C content Gram-positive), and Wigglesworthia and Buchnera for gamma proteobacteria.^[10]

Some of the largest virions like Megavirus chilensis, Pandoravirus, Pithovirus and mimivirus are comparable in size to miniature bacteria like T. whipplei and Rickettsia conorii.

Further reading

• Fournier PE, Zhu Y, Ogata H, Raoult D . Use of Highly Variable Intergenic Spacer Sequences for Multispacer Typing of Rickettsia conorii Strains . J. Clin. Microbiol. . 42 . 12 . 5757–66 . December 2004 . 15583310 . 535242 . 10.1128/JCM.42.12.5757-5766.2004 .
• La Manna. Torina A, Agnone A. Detection of Natural Killer T Cells in Mice Infected with Rickettsia conorii. November 2013. 60. 80–85.

Notes and References

1. Book: Yu. XJ. Walker. DH. Brenner. DJ. Krieg. NR. Staley. JT. 3 . Garrity. GM. 2005. Bergey's Manual of Systematic Bacteriology, Volume 2, Part C. Genus I. Rickettsia da Rocha-Lima 1916, 567^AL. 2nd. Springer. New York. 10.1007/0-387-29298-5_28. 2024-04-27.
2. Parola, P . Paddock, CD . Raoult, D . Tick-Borne Rickettsioses around the World: Emerging Diseases Challenging Old Concepts. Clin Microbiol Rev . 18 . 719–756 . 2005 . 10.1128/CMR.18.4.719-756.2005 . 16223955 . 1265907 . 4.
3. Brumpt, E. Longevité du virus de la fièvre boutonneuse (Rickettsia conorii, n. sp.) chez la tique Rhipicephalus sanguineus. C. R. Soc. Biol. . 110 . 1119–1202 . 1932.
4. Conor, A . A Bruch . amp . Une fièvre éruptive observée en Tunisie. Bull Soc Pathol Exot Filial . 8 . 492–496 . 1910.
5. Zhu Y, Fournier PE, Eremeeva M, Raoult D . Proposal to create subspecies of Rickettsia conorii based on multi-locus sequence typing and an emended description of Rickettsia conorii . BMC Microbiol. . 5. 11 . 2005 . 15766388 . 1079849 . 10.1186/1471-2180-5-11 . free .
6. Ogata H, Audic S, Renesto-Audiffren P, etal . Mechanisms of evolution in Rickettsia conorii and R. prowazekii . Science . 293 . 5537 . 2093–8 . September 2001 . 11557893 . 10.1126/science.1061471 . 2001Sci...293.2093O . 35985908 .
7. Sentausa E, El Karkouri K, Robert C, Raoult D, Fournier PE . Genome sequence of Rickettsia conorii subsp. indica, the agent of Indian tick typhus . J. Bacteriol. . 194 . 12 . 3288–9 . June 2012 . 22628514 . 3370856 . 10.1128/JB.00462-12 .
8. Sentausa E, El Karkouri K, Robert C, Raoult D, Fournier PE . Genome sequence of Rickettsia conorii subsp. caspia, the agent of Astrakhan fever . J. Bacteriol. . 194 . 17 . 4763–4 . September 2012 . 22887666 . 3415478 . 10.1128/JB.00992-12 .
9. Sentausa E, El Karkouri K, Robert C, Raoult D, Fournier PE . Genome sequence of Rickettsia conorii subsp. israelensis, the agent of Israeli spotted fever . J. Bacteriol. . 194 . 18 . 5130–1 . September 2012 . 22933760 . 3430316 . 10.1128/JB.01118-12 .
10. Tropheryma whipplei Twist: A Human Pathogenic Actinobacteria with a Reduced Genome. 10.1101/gr.1474603. 2003. Raoult. Didier. Ogata. Hiroyuki. Audic. Stéphane. Robert. Catherine. Suhre. Karsten. Drancourt. Michel. Claverie. Jean-Michel. Genome Research. 13. 8. 1800–1809. 12902375. 403771.