Diversity and Molecular Characterization of Shiga Toxin-producing Escherichia coli Isolated from Ground Beef at Point of Sale in Hidalgo, Mexico

Shiga toxin-producing Escherichia coli (STEC) is the causative agent of several epidemic outbreaks worldwide. STEC infections range from mild diarrhea to fatal outcomes, transmission occurs mainly through the ingestion of contaminated and undercooked meat. The objective of the present study was to identify STEC strains in ground beef samples and characterize virulence genes associated with a public health risk. Thirteen E. coli strains were analyzed from 10 ground beef samples collected in Hidalgo, Mexico. The stx1, stx2, eaeA and hlyA genes were detected by multiplex PCR, and Enterobacterial Repetitive Intergenic Consensus (ERIC) sequences of were amplified by endpoint PCR. Of the 13 strains analyzed, 11 (84.61%) carried the stx1 and stx2 genes, while 6 strains (46.15%) also harbored the eaeA gene; none carried the hlyA gene. Analysis of ERIC-PCR banding patterns revealed clustering of isolates at 50% genetic similarity, in addition thirteen distinct genetic profiles were identified, with no evidence of clonality among the samples. This study confirms the contamination of ground beef with STEC, demonstrating high genetic diversity and the presence of key virulence genes (stx1, stx2 and eaeA). The characteristics of the isolates highlight their zoonotic potential and underscore the role of ground beef as a significant vehicle for foodborne illness.