Phylogenetic Characterization of Strains from Oysters and its Comparison with Clinical E Genotype Strain.

Twenty-one environmental strains from the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) bacteria collection, 20 of them isolated from oyster samples and 1 from a reported clinical case, were sequenced to analyze the genomic divergence between 2 genotypes, E-genotype and C-genotype, proposed by various groups to distinguish clinical (C) from environmental (E) strains. As indicated in previous analyses of PFGE, MLST, and A, 9 of the CICESE isolates were identified as E, compared with 12 as C. Separation of the genotypes into these 2 groups was confirmed in this study, based on the presence of certain genes in the 21 genomes, the presence of virulence factors, and A sequencing. Most genomes from oyster isolates expressed A-C type, with the exception being A-M type detected in CICESE-594 a E strain isolated from a clinical case. Although several genetic approaches clearly indicate differences between the C- and E-genotypes, none of them, including those in this study, can highlight a single factor that could be used to indicate the potential pathogenicity of isolated from oysters.