Multidrug Resistance of Escherichia coli Strains Isolated From Bovine Feces and Carcasses in Northeast Mexico

Abstract

In this work, the antimicrobial resistance profile of <i>Escherichia coli</i> strains (<i>n</i> = 248) isolated from bovine feces and carcass samples from Tamaulipas, Mexico, was evaluated. Susceptibility to 12 antibiotics conventionally used in human and veterinary treatments was determined according to Clinical and Laboratory Standards Institute guidelines. Genes encoding resistance to tetracycline (<i>tetA</i> and <i>tetB</i>), streptomycin (<i>str</i>A), aminoglycoside (<i>aad</i>A), and β-lactamase (<i>bla</i> _TEM and <i>bla</i> _SHV) were investigated by PCR. Also, <i>stx</i>1, <i>stx</i>2, <i>eae, bfp</i>, and <i>hly</i>A encoding virulence factors were determined. Of the isolates, 85.9% were confirmed as <i>E. coli</i> strains. Among the 213 <i>E. coli</i> isolates tested, 94.8% (202/213) showed resistance for at least one antimicrobial, mainly ampicillin (83.0%; 177/213), cephalothin (76.0%; 162/213), and tetracyclines (69.0%; 147/213). In all the other antibiotics tested, the resistance percentage was below 36%. A multidrug-resistant phenotype was found in 72.7% of the tested strains. The presence of the <i>tet</i> gene (<i>tet</i>A or <i>tet</i>B) was detected in 43.1% of the isolates, the <i>str</i>A gene in 17.3%, and <i>aad</i>A1 in 51.6%. The <i>bla</i> _TEM and <i>bla</i> _SHV genes were found in 10.3 and 0.4% of the isolates, respectively. <i>stx</i>1 was detected in 4.2% of isolates, <i>stx</i>2 in 7.0, and <i>hly</i>A in 2.8%. The virulence genes, <i>eae</i> and <i>bfp</i>, were not detected in any strain. These results indicate that Tamaulipas food products of bovine origin can be a source of multiresistant <i>E. coli</i> strains for the environment and exposure for consumers.