Comparison of phenotypic and genotypic antimicrobial profiles in Escherichia coli and Salmonella enterica from the same dairy cattle farms

Transmission of antimicrobial drug resistance from resistant bacteria to non-resistant strains is an important public health issue. In this study, we have examined the possibility of multiple resistance gene transfer between Escherichia coli and Salmonella in the natural setting. Bacteria isolated from calves concurrently shedding E. coli and Salmonella showed similar antimicrobial drug resistance patterns as measured by a broth dilution method. However, microarray analysis of the antibiotic resistance at the gene level revealed several differences in resistance gene profile. Resistance profiles of E. coli isolated from different farms were closer than the profile of E. coli and Salmonella isolated from the same farm. This shows that the chance of multiple resistance gene transfers between these species is unlikely.