Bacteriological and Molecular Identification of E. coli Isolated from Clinical and Subclinical Mastitis in Cattle and Buffalo

Escherichia coli (E. coli) is one of the most significant pathogens causing mastitis, one of the most complex and costly diseases in the dairy industry worldwide. This study aimed to isolate E. coli, detect virulence factors, assess antimicrobial susceptibility, and identify resistance genes in cows and buffaloes with clinical and subclinical mastitis.A total of 330 cows and 70 buffaloes were examined for clinical and subclinical mastitis. From cows, 50 clinical and 50 subclinical mastitis milk samples were collected, and from buffaloes, 30 clinical and 10 subclinical samples were collected. These samples were subjected to bacteriological identification, biochemical tests, antibiotic sensitivity testing, and molecular analysis.E. coli was isolated from 16/50 (32%) clinical and 5/50 (10%) subclinical mastitis samples from cows, and from 3/30 (10%) clinical and 1/10 (10%) subclinical samples from buffaloes. Antibiotic sensitivity testing revealed high resistance to oxytetracycline (48%), cefotaxime (24%), and streptomycin, gentamicin, and nalidixic acid (20%). Molecular analysis detected five virulence genes: fimA was the most prevalent gene, occurring in 83.3% of all isolates (clinical and subclinical). papC followed, present in 50% of isolates. The prevalence of iss and ompT was higher in subclinical isolates (66.6% for both) compared to clinical isolates (50% for iss and 44.4% for ompT). Conversely, iucD was slightly more common in clinical isolates (44.4%) than in subclinical ones (33.3%)..E. coli was identified as a major bacterial pathogen involved in bovine clinical and subclinical mastitis