MOLECULAR CHARACTERIZATION OF BORRELIA-BURGDORFERI SENSU-LATO FROM SLOVENIA REVEALING SIGNIFICANT DIFFERENCES BETWEEN TICK AND HUMAN ISOLATES

One hundred twenty-nine Slovenian isolates of Borrelia burgdorferi sen su late derived from patients (69 strains) or Ixodes ricinus ticks (60 strains) were characterized. All of the strains were first- or second -passage isolates obtained in 1992 and 1993 from the same endemic regi on. The techniques used for the molecular analysis of strains included species-specific polymerase chain reaction (PCR) typing, and pulsed-f ield gel electrophoretic separation of undigested and Mlul-digested ge nomic DNA. isolates were identified to the species level by large rest riction fragment pattern (LRFP) analysis and the results compared with the species-specific PCR result. Fifty-two patient isolates (75%) wer e typed as Borrelia afzelii (LRFP MLa1), 6 (9%) as Borrelia garinii (L RFPs MLg1-4), and 11 (16%) as Borrelia burgdorferi sensu stricto. The latter included 9 isolates (13%) with a new LRFP that is not typical o f Borrelia burgdorferi sensu stricto and for which the designation MLx is suggested. In contrast, only 32 of 60 (53%) tick isolates were typ ed as Borrelia afzelii, while 20 strains (33%) were typed as Borrelia garinii and 8 strains (13%) as Borrelia burgdorferi sensu stricto. Thr ee new LRFPs were found among the Borrelia garinii (MLg5 and 6) and Bo rrelia burgdorferi sensu stricto (MLb15) tick isolates. Large restrict ion fragment pattern analysis identified new groups of Borrelia burgdo rferi sensu late and revealed an apparent difference in the isolation frequency of different species from patients and ticks in the same end emic region.