Shiga toxin–producing Escherichia coli (STEC) is a food-borne pathogen that can cause diarrhea, sometimes complicated by hemolytic-uremic syndrome (HUS). Cattle and other ruminants are the major reservoirs. STEC produces two potent cytotoxins (Stx1, Stx2) that inhibit protein synthesis. In humans, another virulence factor is the outer membrane protein intimin, encoded by the eae gene.

In this study, 9 STEC strains isolated from dogs and cats were tested for a range of virulence factors, genetic relationships with strains from cattle, and cytotoxic activity. All 9 strains showed cytotoxic activity. None of the strains possessed the genes subAB, eae, or saa, which encode for virulence factors. Only strains belonging to the subtype O8:H19 carried the exhA gene, which encodes for the virulence factor enterohemolysin. The 9 isolates were 90% to 100% similar to serotypes recovered from cattle, meat, and humans; several STEC strains belonged to pathotypes associated with human disease, including HUS. The virulence patterns suggested the source may be from bovine meat fed to pets by their owners. Pets may have an epidemiologic role as a source of STEC infections in humans.

Outbreaks of STEC are commonly a result of E coli 0157; however, other strains of STEC serogroups also can cause severe illness in humans of all ages. A severe complication of STEC illness that occurs in 5% to 10% of infected humans is HUS. This study revealed that companion dogs and cats can harbor serogroups of STEC that are 90% to 100% genetically similar to strains of corresponding serotypes recovered from cattle, meat, or humans. Although only 9 isolates were examined, the genetic similarity to previous outbreak strains and the presence of putative virulence factors in these strains highlighted that pets could potentially be silent reservoirs of STEC.—Faye Hartman, MS, MT (ASCP)

Profile of Shiga toxin-producing Escherichia coli strains isolated from dogs and cats and genetic relationships with isolates from cattle, meat and humans. Bentancor A, Rumi MV, Carbonari C, et al. VET MICROBIOL 156:336-342, 2012.

This capsule is part of the One Health Initiative