Prevalence of shiga-like toxin-producing escherichia coli in "Sarda" slaughtered sheep: direct detention of virulence genes and molecular characterization of non-0157 isolates

A study of pathogenic Escherichia coli in Sarda sheep at slaughter, on carcasses, fleeces, gut and faeces was performed. Nineteen sampling sessions were carried out from January 2009 to May 2010. Specimens were taken from local ewes and suckling lambs, and collected from industrial capacity slaughterhouses. The aim of the present study was to evaluate the role of the sheep as VTEC reservoir and to detect the prevalent serogroups over the sheep chain production. In order to make a preliminary screening of VTEC in collected samples, a simplex PCR was performed on all the specimens. Isolation of colonies were performed by immunomagnetic separation and culture onto CT-SMAC, CT-RMAC, EHLY agar. Real time PCR serotyping and virulence profile characterization by PCR were executed on isolated strains. Preliminary screening method reveals a prevalence of VTEC in sheep of 32.6% with higher level in fleeces (18.9%), indicating that these matrices might be considered as a risk for cross-contamination. Virulence profile characterization of the isolates showed a significant level of VTEC strains (22.6%) and a higher number of EPEC (53.8%). Furthermore, virulence accessory factors are widely detected, assigning an additional pathogenic capacity to the strains, and very complex virulence profiles. Serotyping assays proved that Sarda sheep carried mainly non-O157 E. coli, including O91 serogroup, the role of these pathogroup in Public Health must not be underestimated.