Abstract
Presence of extended-spectrum β-lactamases (ESBL)-producing Enterobacteriaceae in the dairy farm environment and food chain could be a possible interface for the exchange of antimicrobial resistance genes between humans and animals. A total of 600 samples comprised of raw bovine milk, faeces, feed, environmental swabs and water samples from 20 different bovine dairy farms in and around Hisar city, Haryana, India were analysed for presence of ESBL encoding genes. Out of 240 isolates of Escherichia coli obtained, 74 isolates were found to be ESBL producers. Maximum number of ESBL isolates were found from faeces (40.5%) followed by raw milk (37.8%) and environmental swabs (17.5%). Most of the ESBL E. coli isolates were sensitive to chloramphenicol (82.4%) and gentamicin (77.0%) antibiotics. The bla (CTX-M) gene was found to be most prevalent (52.0%) followed by bla (TEM) (9.45%) while bla (SHV) gene alone was not detected in any sample by simplex PCR. However, the co-expression of bla(CTX-M) + bla(TEM) (21.6%) and bla(CTX-M) + bla(SHV) (4.05%) genes were also observed. The housing system, milking method and the hygienic mangement practices followed at farm level are found to be significant risk factors of ESBL-producing E. coli in dairy farms of Haryana.