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Although E. coli O157 is the most common Shiga toxin-producing strain of E. coli associated with foods of bovine origin, other strains (serotypes) of E. coli can also cause similar infections and have become more common than E. coli O157 in other parts of the world. The goal of this study was to determine how these new strains of E. coli might end up in cattle. Cattle might become contaminated with these strains from other sources. Alternatively, it is considered possible the new strains of Shiga toxin-producing E. coli may emerge by sampling acquiring the ability to produce Shiga toxin from E. coli O157 following the exchange of genetic material.
Findings: This study found that the use of antibiotics typically used to treat illnesses in feedlot animals did not appear to increase the rate of genetic exchange that occurred in the lab. Importantly, when the frequency of genetic exchange of toxin genes was followed in live animals, the event occurred so rarely that it was not detectable. Furthermore, using molecular epidemiological tools, it was demonstrated that the genes associated with the Shiga toxins in E. coli O157 were considerably different than those present in non-O157 STEC. Taken together, these data strongly suggest that current livestock management practices do not promote the emergence of new strains of pathogenic E. coli from the current pool E. coli O157 in US livestock populations. Instead, preventing non-O157 E. coli in US cattle will rely on prevention of highly pathogenic non-O157 from being introduced to cattle sources from outside sources.
<P> For complete projects details, view the <a href="http://www.beefresearch.org/CMDocs/BeefResearch/Phage-Encoded%20Dissemi…; target="_blank">Project Summary. </a>