Twenty-four month longitudinal study suggests little to no horizontal gene transfer in situ between third-generation cephalosporin-resistant Salmonella and third-generation cephalosporin-resistant Escherichia coli in a beef cattle feedyard

What is it about?

It has been theorized that Salmonella present at cattle feedyards may become resistant to the primary antibiotic used to treat serious human Salmonella infections by acquiring the genes responsible for resistance from non-pathogenic resistant E. coli. This theory has not been tested although this gene transfer can be shown in artificial laboratory conditions, it has not been conclusively demonstrated in real world conditions. This study characterized resistance genes in 242 Salmonella and 203 E. coli isolated from a beef feedyard over two years. The primary resistance gene in resistant Salmonella was present in only 37.9% of the resistant E. coli. Likewise, the primary resistance gene in most resistant E. coli was at low levels in resistant Salmonella. These results demonstrated that resistant Salmonella at this feedlot were primarily due the persistence of a well-adapted Salmonella sub-population with very minimal or no contribution of resistance genes from E. coli.

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