Phylogenetic analysis of enterohemorrhagic Escherichia coli O157, Germany, 1987-2008

Abstract

Multilocus variable number tandem repeat analysis (MLVA) is a subtyping technique for characterizing human pathogenic bacteria such as enterohemorrhagic Escherichia coli (EHEC) O157. We determined the phylogeny of 202 epidemiologically unrelated EHEC O157:H7/H-clinical isolates through 8 MLVA loci obtained in Germany during 1987-2008. Biodiversity in the loci ranged from 0.66 to 0.90. Four of 8 loci showed null alleles and a frequency <44.1%. These loci were distributed among 48.5% of all strains. Overall, 141 MLVA profi les were identifi ed. Phylogenetic analysis assigned 67.3% of the strains to 19 MLVA clusters. Specifi c MLVA profi les with an evolutionary persistence were identifi ed, particularly within sorbitol-fermenting EHEC O157:H-. These pathogens belonged to the same MLVA cluster. Our fi ndings indicate successful persistence of this clone.