SNP genotyping of Escherichia coli O157:H7 bovine strains isolated in Argentina

MERCADO EC; RABINOVITZ BC; LARZÁBAL M; VILTE DA; CATALDI A; MANNING SD

Congreso; I Congreso Internacional de Zoonosis y Enfermedades Emergentes y VII Congreso Argentino de Zoonosis; 2011

Escherichia coli O157:H7, a Shiga toxin-producing bacteria, is frequently asociated with gastrointestinal illness and hemolytic uremic syndrome (HUS) in humans, although factors that contribute to variation in disease severity are poorly understood. Nine phylogenetically distinct clades comprising 39 SNP genotypes (SGs) were previously identified among 538 O157 clinical strains. Clade 8 strains were more frequently isolated from HUS cases than strains of other clades.  Because of the high incidence of HUS in Argentina, we sought to determine whether clade 8 strains are in circulation outside of North America, the site of the prior study. In this study we screened 6 E. coli O157: H7 bovine strains isolated from 4 different farms in 3 provinces of Argentina for the SNP present at 32 different loci; these loci were previously found to differentiate the clades and most SGs within the clades. The analysis showed that only 2 of the 6 strains represented SGs that were identified previously (using the minimal SNP set versus screening all 96 loci). Indeed, these 2 strains were classified as clade 8 (1 was SG-30 and 1 was SG-31). The other 4 strains, however, had novel SNP profiles and represent distinct clades in a Neighbor-joining phylogeny resconstructed with SNP data from strains of all nine clades identified previously. All 6 of the strains harbored stx2 and stx2c genes and the eae gamma allele. These results show that Argentinean cattle carry strains from clade 8, the lineage associated with more severe human disease, as well as strains of unique phylogenetic lineages. It is therefore possible that clade 8 represents a widespread, successful lineage, and that the novel SGs identified in this analysis are unique to Argentina and/or bovines.