CLASSIFICATION OF ITALIAN ISOLATES OF BORRELIA-BURGDORFERI INTO 3 GENOMIC GROUPS

In this study we investigated the genotypic characteristics of some lo cally isolated strains of B. burgdorferi by three different methodolog ies: restriction endonuclease analysis (REA), Southern blot hybridizat ion with whole DNAs from Borrelia strains and Southern blot hybridizat ion with rRNA 16+23S genes derived from E. coli. REA fingerprintings w ere evaluated by cluster analysis, according to the principles of nume rical taxonomy. The genomas of the locally isolated strains were compa red with borreliae originating from different countries of Europe, inc luding Sweden and with the American reference strain B31. Among the Eu ropean strains, some already described by Baranton (Baranton et al., 1 992) as representatives of different genomic groups Borrelia sensu str icto and Borrelia garinii were used. By the different techniques the i solates were included in three genomic groups which could correspond t o the three genospecies identified by Baranton, namely B. burgdorferi sensu stricto, B. garinii and B. group VS461: in fact two strains were included in a homogeneous group, probably corresponding to the VS461 genomic group, together with other European borreliae; one isolate was included in a group consisting of B31 and some other European strains already described as belonging to Borrelia burgdorferi in sensu stric to. Finally two isolates were ascribed to a third genomic group probab ly corresponding to the genospecies indicated as Borrelia garinii. The se findings indicate that a small number of Borrelia strains isolated from a very restricted area can be genetically heterogeneous.