Screening of AmpC-/ESBL-producing Escherichia coli isolates from livestock for STEC/EHEC virulence genes

Livestock is an important reservoir of Shiga toxin-producing Escherichia coli and enterohemorrhagic E. coli (STEC/EHEC) strains and acts as a significant source of transmission to humans. In addition to the virulence of STEC/EHEC isolates, antibiotic resistance is also an escalating problem in these bacteria and increases the risk to public health. Therefore, the present study aimed to explore E. coli O-157:H(7 )serotype and STEC/EHEC virulence genes in AmpC- and extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates from cattle, chicken and sheep. A total of 61 confirmed AmpC- or ESBL-producing E. coli isolates were screened for the virulence genes (stx1, stx2, eae, ehxA, espP, katP and saa) and E. coli O-157 (rfbO(157)) and H-7 (fliCH(7)) genes by polymerase chain reaction (PCR). None of the ESBL-producing E. coli was positive for these genes, but six multidrug-resistant AmpC-producing E. coli were positive for the fliCH(7) gene only. When considering the function of the H-7 flagellar antigen of E. coli, it may be concluded that the development of ESBL/AmpC beta-lactamase production in the E. coli isolates with H-7 flagella, which reside in the chicken intestine, may be potentially important for public health regarding both virulence and antimicrobial resistance.