Abstract
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 O130:H11 and O178: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 O130:H11 isolates, stx2EDL933 was the predominant subtype. In O178:H19 isolates the main stx2 subtype was stx2vha. The sab gene was detected in 65 and 24% of the isolates belonging to O130:H11 and O178:H19, respectively. Only one MLVA profile was identified among the O130:H11 isolates meanwhile 10 MLVA profiles were detected among the O178:H19 isolates which were grouped in two main clusters. In conclusion, our data show that O130:H11 and O178: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 stx2 subtype and the presence/absence of sab gene, and for isolates belonging to O178:H19, also when the MLVA type was considered. However, MLVA subtyping of O130:H11 isolates will require the development of more specific markers.
Highlights
Shiga toxin-producing E. coli (STEC) cause bloody diarrhea, hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) in humans (Pearce et al, 2004; Giugno et al, 2007)
Our subtyping experiments showed that isolates could be distinguished based on the stx2 subtype and the presence/absence of sab gene, and for isolates belonging to O178:H19, when the multiple-locus variable-number tandem repeat analysis (MLVA) type was considered
The subtypes found in this work have been reported as the predominant sxt2-subtypes in bovine STEC strains in Argentina and other countries (Bertin et al, 2001; Brett et al, 2003; Meichtri et al, 2004; Galli et al, 2010; Krüger et al, 2011) and have been associated with the development of HC and HUS (Friedrich et al, 2002; Persson et al, 2007)
Summary
Shiga toxin-producing E. coli (STEC) cause bloody diarrhea, hemorrhagic colitis (HC) and hemolytic uremic syndrome (HUS) in humans (Pearce et al, 2004; Giugno et al, 2007). Cattle are the main reservoir of STEC and the transmission to humans occurs through the consumption of undercooked meat, non-pasteurized dairy products, and vegetables or water contaminated with feces (Hussein and Sakuma, 2005). The main virulence factor of STEC is the production of Shiga toxins (Stx and Stx2) (Paton and Paton, 1998; Gyles, 2007). Stx subtypes differ in their degree of association with HC and HUS cases, being Stx2O118 (formerly identified as Stx2d-Ount), Stx2e, Stx2f, and Stx2g not frequently associated with severe human disease (Friedrich et al, 2002; Karch et al, 2005; Prager et al, 2009, 2011). The ehxA, saa, and sab genes are Frontiers in Cellular and Infection Microbiology www.frontiersin.org
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
