Proteinic and genomic identification of spotted fever group rickettsiae isolated in the former USSR

Abstract

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), restriction fragment length polymorphism of polymerase chain reaction- amplified genes (RFLP-PCR), and pulsed-field gel electrophoresis (PFGE) were used to identify 25 isolates of spotted fever group rickettsiae collected in the former USSR. Six Rickettsia akari isolates which were identical to the MK reference strain from the American Type Culture Collection were found. Also, 14 isolates were found to be Rickettsia sibirica and identical to reference strain 246. Two of three isolates previously considered as atypical, low- pathogenic strains of R. sibirica, were found to be strains of Rickettsia slovaca. The third, strain S, was similar in its RFLP-PCR profile to 'R. africae' sp. nov. (proposed name for a rickettsia pathogenic for human beings in southern Africa) but in its SDS-PAGE and PFGE profiles was unique among spotted fever group rickettsia. Strain M-1 was confirmed as a genetic variant of Rickettsia conorii. The Astrachan isolate, the causative agent of a tick- bite rickettsiosis at the North of the Caspian Sea, showed a previously described RFLP-PCR profile identical to that of the Israeli tick typhus rickettsia, but its SDS-PAGE and PFGE profiles different from those of the other strains tested.