Molecular characterisation of Lyme disease borreliae using RAPD analysis and 16S rDNA sequencing.

Here we report the use of random amplified polymorphic DNAs (RAPDs) and sequence analysis of the genes encoding for the small subunit ribosomal RNA (16S rDNA) for the characterisation of Borrelia burgdorferi sensu lato strains recovered from Ixodes ricinus and from Lyme disease patients. All strains examined were assigned to the species Borrelia garinii. However, both RAPDs and 16S rDNAs revealed a level of genetic variation among the strains which appears higher than expected for a bacterial species. In addition, the data obtained agree with the clonal theory applied to Borrelia burgdorferi s.l. for explaining some traits of its epidemiology. According to this theory, particular strains should spread rapidly, leading to the diffusion of bacteria with a particular chromosomal genotype. Our results reveal high genetic variation even among strains isolated in the same period from a restricted geographic area. Moreover, the data here reported indicate that clonal diffusion of antigenic characteristics could also occur.