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Origins, Importance and Genetic Stability of the Prototype Strains Gilliam, Karp and Kato of Orientia tsutsugamushi

1
Viral and Rickettsial Diseases Department, Naval Medical Research Center, Silver Spring, MD 20910, USA
2
Department of Evolution, Ecology and Organismal Biology, The Ohio State University, Columbus, OH 43210, USA
3
Department of Preventive Medicine and Biostatistics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA
*
Author to whom correspondence should be addressed.
Trop. Med. Infect. Dis. 2019, 4(2), 75; https://doi.org/10.3390/tropicalmed4020075
Received: 8 March 2019 / Revised: 17 April 2019 / Accepted: 24 April 2019 / Published: 30 April 2019
(This article belongs to the Special Issue The Past and Present Threat of Rickettsial Diseases)
Scrub typhus, a chigger-borne febrile illness, occurs primarily in countries of the Asia-Pacific rim and islands of the Western Pacific. The etiologic agent is the obligate intracellular rickettsial bacterium Orientia tsutsugamushi. Research on O. tsutsugamushi has relied on the availability of several prototype strains, which were isolated from human cases of scrub typhus in the 1940s and 1950s. We review the history of the three original, and most important, prototype strains, Gilliam, Karp and Kato, including information on their isolation, their culture history, their clinical characteristics, their importance within the research literature on scrub typhus, and recent advances in elucidating their molecular genomics. The importance of these strains to the research and development of clinical tools related to scrub typhus is also considered. Finally, we examine whether the strains have been genetically stable since their isolation, and whether prototype strains maintained in separate laboratories are identical, based on pairwise comparisons of several sequences from four genes. By using genetic information archived in international DNA databases, we show that the prototype strains used by different laboratories are essentially identical, and that the strains have retained their genetic integrity at least since the 1950s. The three original prototype strains should remain a standard by which new diagnostic procedures are measured. Given their fundamental position in any comparative studies, they are likely to endure as a critical part of present and future research on scrub typhus and Orientia. View Full-Text
Keywords: Orientia; scrub typhus; Gilliam; Karp; Kato; O. tsutsugamushi; comparative genomics; genetic stability; serogroups Orientia; scrub typhus; Gilliam; Karp; Kato; O. tsutsugamushi; comparative genomics; genetic stability; serogroups
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Kelly, D.J.; Fuerst, P.A.; Richards, A.L. Origins, Importance and Genetic Stability of the Prototype Strains Gilliam, Karp and Kato of Orientia tsutsugamushi. Trop. Med. Infect. Dis. 2019, 4, 75.

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