Characterization of Shiga toxin-producing Escherichia coli O130:H11 and 0178:H19 isolated from dairy cows

Shiga toxin-producing E. coli (STEC) are isolated from human patients with bloody diarrhea, hemorrhagic colitis (HC), and hemolytic uremic syndrome (HUS). In the last years, the infections with non-O157 serotypes are increasing their frequency of association with human disease. STEC produce Shiga toxin (Stx) and other virulence factors that could contribute to human pathogenesis. Cattle are the main reservoir and the transmission to humans is through the consumption of undercooked meat, non-pasteurized dairy products, and vegetables or water contaminated with feces. We have previously determined that O130:H11 and O178:H19 serotypes were the most prevalent in dairy cows from Argentina. In the present study, 37 and 25 STEC isolates from dairy cows belonging to 0130:H11 and 0178:H19 serotypes, respectively, were characterized regarding to their cytotoxicity on Vero cells, stx subtypes, presence of sab and typing by multiple-locus variable-number tandem repeat analysis (MLVA). All strains demonstrated a cytotoxic effect, and in 0130:H11 isolates, stx2(EDL933) was the predominant subtype. In O178H19 isolates the main stx2 subtype was stx2(vha). The sab gene was detected in 65 and 24% of the isolates belonging to 0130:H11 and 0178:H19, respectively. Only one MLVA profile was identified among the 0130:H11 isolates meanwhile 10 MLVA profiles were detected among the 0178:H19 isolates which were grouped in two main clusters. In conclusion, our data show that 0130:H11 and 0178:H19 STEC isolates encode virulence factors associated with severe human disease and both serotypes should be considered for routinely testing. Our subtyping experiments showed that isolates could be distinguished based on the stx(2) subtype and the presence/absence of sab gene, and for isolates belonging to 0178:H19, also when the MLVA type was considered. However, MLVA subtyping of O130H11 isolates will require the development of more specific markers.