Genetic and phenotypic characterization of Borrelia burgdorferi strains isolated from Ixodes ricinus ticks in the Province of Bolzano, Italy.

Lyme disease is caused by three borrelial species, B. burgdorferi sensu stricto, B. garinii and Borrelia group VS461. In a restricted biotope of the Bolzano province, in the Caldaro community, five clones of two borrelial variants were isolated from Ixodes ricinus ticks. A preliminary serological study showed that the two variants cross-reacted with B. burgdorferi B31 and B. garinii N34 strains, respectively. The isolates were genomically related with strains B31 and N34, respectively, sharing a similar plasmid and restriction fragment length polymorphism profile with these strains. The phenotypic pattern of the Caldaro isolates-namely their protein and antigenic profile-showed infra-subspecific variation compared to related strains B31 and N34 respectively. The observed phenotypic variability between strains isolated from the same biotope and in the same tick host strongly indicated the variability of gene-encoded characters is a constant characteristic of borrelial strains, even when from the same ecological niche.