GENOTYPIC AND PHENOTYPIC ANALYSIS OF BORRELIA-BURGDORFERI ISOLATES FROM THE NETHERLANDS

Sixty-three Borrelia burgdorferi isolates recovered from Ixodes ricinu s ticks collected in 17 locations in The Netherlands and three Dutch h uman skin isolates were characterized by rRNA gene restriction fragmen t length polymorphism, sodium dodecyl sulfate-polyacrylamide gel elect rophoresis, and Western blotting (immune-blotting). All three human is olates belonged to B. burgdorferi group VS461. Of the tick isolates, 2 9 (46%) were B. burgdorferi sensu stricto, 2 (3%) were group VS461, 19 (30%) were Borrelia garinii, and 13 (21%) were different from any pre viously described genomic species. On the basis of the criteria descri bed, 12 isolates formed a distinct genomic group, designated M19. rRNA gene restriction patterns of the group M19 isolates resembled but wer e not identical to the B. garinii patterns. Hybridization of digested DNA with a flagellin probe confirmed the separation of group M19 from the B. garinii isolates. One isolate, M63, was different from ail the others. In conclusion, the occurrence of B. burgdorferi sensu stricto, B. garinii, and B. burgdorferi group VS461 in ticks from The Netherla nds corresponds with the occurrence of these genomic species among tic k isolates from other European countries. However, our findings sugges t that B. burgdorferi sensu late probably contains more than three gen omic species.