Sample collection and identificationA total of 180 lactating animals (166 cows and 14 buffalo) were sampled from seven farms. Before collection of clinical samples, a brief history of various animal

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Pathogenic E. coli associated with bovine mastitis are least studied group of microbes in India. Thus an investigation was carried out to know the occurrence of bovine subclinical mastitis and E. coli at different dairy farms. E. coli strains isolated from clinical and environmental samples were screened for virulent genes namely, eae, bfpA, iapH, aggR, elt, est, stx1/stx2; phylogenetic groups and for ESBL production. Findings revealed high prevalence of subclinical mastitis (45%). E. coli strains were isolated from milk, udder, milking machine, floor swabs, etc. Out of 81 E. coli, 38 (46.91%) were ESBL producers. The virulent genes in single or in combination were detected in 55 strains and eae gene was predominant (43.20%). The stx1/stx2 were detected in 2.47% samples. E. coli isolates fall under phylogenetic groups B1 (58.18%), A (23.63%) and D (18.18%). Phylogenetic group B2 was not detected. Dairy cattle could act as a reservoir of ESBL type diarrheagenic E. coli.