CHARACTERIZATION OF BORRELIA-BURGDORFERI ISOLATED FROM DIFFERENT ORGANS OF IXODES-RICINUS TICKS COLLECTED IN NATURE

Borrelia burgdorferi was isolated from 22 out of 133 adult Ixodes rici nus ticks collected from vegetation at two sites in Switzerland. From 17 ticks, spirochetes could be isolated from more than one organ. When the different isolates obtained from one tick were compared by SDS-PA GE analysis, differences in the protein profiles were observed in 8 ca ses. The isolates were further compared by immunological methods using mono- and polyclonal antibodies. Differences were observed in the pro teins of 31-35 kDA and 18-25 kDa. Genetic divergence among isolates wa s evaluated by use of a B. burgdorferi specific gene probe for ospA. C orrelation could be observed between immunological differences in OspA defined by monoclonal antibody LA31 and genetic variation of ospA as judged by restriction fragment length polymorphism (RFLP). Our finding s indicate that systemic infection in unfed I. ricinus adults, as refl ected by isolation of B. burgdorferi from multiple organs of one tick, is more frequent (8/22, 36%) than previously described (5%). Moreover , the presence of different B. burgdorferi phenotypes/genotypes in one tick is described for the first time. The findings may have bearings (i) on the time of tick attachment required for spirochete transmissio n since borreliae are already present in the salivary glands of system ically infected ticks at the beginning of the blood meal and (ii) perh aps also on the diversity of B. burgdorferi phenotypes inoculated by t hese ticks.