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

Abstract

Five strains of spotted fever group (SFG) rickettsiae previously isolated from human clinical cases and from the tick Haemaphysalis leporispalustris were used for molecular characterization in this study to establish their genetic relationship compared with the prototype Rickettsia rickettsii strain Sheila Smith. Samples were tested by polymerase chain reaction (PCR) targeting the rickettsial genes gtlA, ompA, and ompB. PCR products of the latter two genes were DNA sequenced and compared with available sequences in GenBank. The ompA partial sequences of the five Costa Rican isolates showed 100% identity to several R. rickettsii sequences available in GenBank, including the sequence of the virulent reference strain Sheila Smith, whereas the ompB partial sequences of the five Costa Rican isolates showed 99.8-100% identity to R. rickettsii sequences from GenBank. This study showed the first molecular detection of R. rickettsii isolates from Rocky Mountain Spotted Fever patients and from the rabbit tick H. leporispalustris in different geographical zones in Costa Rica.

Phylogeography of Rickettsia rickettsii Genotypes Associated with Fatal Rocky Mountain Spotted Fever

“…35,36 Limited genetic analyses of a Costa Rica Hlp isolate reveals complete identity with several United States isolates of R. rickettsii, including the Hlp #2 and Sheila Smith strains. 37 Collectively, these data reinforce the observation that the severity of disease caused by a particular strain of R. rickettsii in a non-human host cannot be extrapolated routinely to the severity of disease in a human host, 7,9,15,34,38 and that additional molecular analyses are needed to better elucidate genetic determinants of virulence in R. rickettsii.…”

Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States

“…For example, R. rickettsii infection can be acquired in Canada and Mexico, as well as in Central America and South America, where cases are reported from Costa Rica, Panama, Brazil, Colombia, and Argentina (253)(254)(255)(256)(257)(258)(259)(260). R. parkeri infections have been described in Uruguay, Brazil, and Argentina (38,253,261,262).…”

Genetic Identification of Rickettsial Isolates from Fatal Cases of Brazilian Spotted Fever and Comparison with Rickettsia rickettsii Isolates from the American Continents

“…1). Interestingly, while low-, mild-, and high-virulent strains of R. rickettsii have been reported in the eastern and western parts of the United States (20,22), only highvirulent strains, responsible for high fatality rates, have been reported in Central/South America, regardless of the tick vector (2,(23)(24)(25)(26)(27)(28)(29). While our results of no polymorphisms among Central/ South American isolates was biased because most of these isolates were derived from fatal cases, a recent study reported the same clade distribution as shown in our Fig.…”