This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Karpathy, S. E. Articles by Eremeeva, M. E. Search for Related Content PubMed PubMed Citation Articles by Karpathy, S. E. Articles by Eremeeva, M. E.

 Previous Article  |  Next Article 

Journal of Clinical Microbiology, August 2007, p. 2545-2553, Vol. 45, No. 8
0095-1137/07/$08.00+0     doi:10.1128/JCM.00367-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Molecular Typing of Isolates of Rickettsia rickettsii by Use of DNA Sequencing of Variable Intergenic Regions

Sandor E. Karpathy, Gregory A. Dasch, and Marina E. Eremeeva^*

Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Atlanta, Georgia 30333

Received 16 February 2007/ Accepted 11 May 2007

Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, is found throughout the Americas, where it is associated with different animal reservoirs and tick vectors. No molecular typing system currently exists to allow for the robust differentiation of isolates of R. rickettsii. Analysis of eight completed genome sequences of rickettsial species revealed a high degree of sequence conservation within the coding regions of chromosomes in the genus. Intergenic regions between coding sequences should be under less selective pressure to maintain this conservation and thus should exhibit greater nucleotide polymorphisms. Utilizing these polymorphisms, we developed a molecular typing system that allows for the genetic differentiation of isolates of R. rickettsii. This typing system was applied to a collection of 38 different isolates collected from humans, animals, and tick vectors from different geographic locations. Serotypes 364D, from Dermacentor occidentalis ticks, and Hlp, from Haemaphysalis leporispalustris ticks, appear to be distinct genotypes that may not belong to the species R. rickettsii. We were also able to differentiate 36 historical isolates of R. rickettsii into three different phylogenetic clades containing seven different genotypes. This differentiation correlated well, but not perfectly, with the geographic origin and likely tick vectors associated with the isolates. The few apparent typing discrepancies found suggest that the molecular ecology of R. rickettsii needs more investigation.

---

* Corresponding author. Mailing address: Rickettsial Zoonoses Branch, Centers for Disease Control and Prevention, Mail Stop G-13, 1600 Clifton Rd. NE, Atlanta, GA 30333. Phone: (404) 639-4612. Fax: (404) 639-4436. E-mail: mge6{at}cdc.gov

Published ahead of print on 6 June 2007.

---

Journal of Clinical Microbiology, August 2007, p. 2545-2553, Vol. 45, No. 8
0095-1137/07/$08.00+0     doi:10.1128/JCM.00367-07
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

This article has been cited by other articles:

• Adjemian, J. Z., Krebs, J., Mandel, E., McQuiston, J. (2009). Spatial Clustering by Disease Severity among Reported Rocky Mountain Spotted Fever Cases in the United States, 2001-2005. Am J Trop Med Hyg 80: 72-77 [Abstract] [Full Text]  
• Hun, L., Cortes, X., Taylor, L. (2008). Molecular Characterization of Rickettsia rickettsii Isolated from Human Clinical Samples and from the Rabbit Tick Haemaphysalis leporispalustris Collected at Different Geographic Zones in Costa Rica. Am J Trop Med Hyg 79: 899-902 [Abstract] [Full Text]  
• Paddock, C. D., Fernandez, S., Echenique, G. A., Sumner, J. W., Reeves, W. K., Zaki, S. R., Remondegui, C. E. (2008). Rocky Mountain Spotted Fever in Argentina. Am J Trop Med Hyg 78: 687-692 [Abstract] [Full Text]