MOLECULAR EVIDENCE SUPPORTING THE EXISTENCE OF 2 MAJOR GROUPS IN UROPATHOGENIC ESCHERICHIA-COLI

Molecular methods allow an extremely fine strain typing that can be us ed to establish the population structure of bacterial species. This me thodology has been used to characterize a collection of 74 uropathogen ic Escherichia coil obtained from three hospitals located in geographi cally distant towns in Spain, some representatives of the ECOR collect ion and other reference strains. Genomic DNA was analyzed by RAPD (Ran dom Amplified Polymorphic DNA) that can characterize a bacterial strai n to the level of defining individual clones. The 16S rDNA-23S rDNA sp acers were amplified by PCR and submitted to restriction analysis. Fin ally, the presence or absence of G adhesins in Escherichia coli as wel l as the type of adhesin (three types are known) have been shown by PC R amplification followed by digestion with restriction enzymes. As exp ected a wide diversity was shown by RAPD and identical patterns were o nly found in the case of strains isolated from the same individual, an obvious case of relapse. Analysis of the spacers' restriction pattern s showed the presence of two markedly differentiated clusters that we have named alpha and beta. Both RAPD and spacer restriction patterns o riginated similar clusters of strains showing a consistency in the evo lution of the global genome with the sequence variation of the ribosom al spacers. Furthermore, most of the strains having G-adhesin, with on ly a few exceptions, corresponded to the alpha rRNA spacer group. The two spacer types detected were also consistent with some phenotypic ma rkers such as sucrose and raffinose utilization. The alpha and beta cl usters could be intraspecific groups produced by partial sexual isolat ion or other barriers that are originating a divergent evolution.