Human and tick spotted fever group Rickettsia isolates from Israel: a genotypic analysis

The genomes of spotted fever group rickettsiae isolated in different geographical areas of Israel (two from ticks and four from humans, obtained over a span of 20 years) were studied by polymerase chain reaction (PCR) and restriction endonuclease fragment length polymorphism (RFLP) analysis. The human isolates were obtained from patients suffering from rickettsial disease of different degrees of severity. The PCR products obtained with five pairs of oligonucleotide primers (two primer sets derived from the 190-kDa polypeptide gene and three from the 120-kDa polypeptide gene) and cleaved with restriction endonucleases were used to study the Israeli isolates and reference Rickettsia conorii isolates. Subtle differences between the PCR-RFLP patterns of Israeli isolates and the two R. conorii reference strains (Moroccan and no. 7) were seen when the PCR products derived from the 190-kDa gene-derived primer sets were digested. All of the Israeli isolates were identical by RFLP analysis using all of the primer sets. This study showed that the Israeli spotted fever group isolates (from both ticks and humans) were genetically homogeneous by the criteria used in this study, despite the time and location differences in their original isolation, and different as a group from R. conorii.