Detection of extended-spectrum beta-lactamase genes among Escherichia coli isolates of buffalo mastitis milk

In recent years, bacteria carrying extended-spectrum beta-lactamase (ESBL) genes have become increasingly prevalent. These genes provide resistance to antibiotics, making treatment more challenging. Escherichia coli is a major cause of mastitis in buffaloes, and there have been reports of ESBL genes in E. coli isolated from bovine mastitis milk. This study was aimed to detect ESBL genes in E. coli found in mastitis buffalo milk. A total of 100 samples of mastitis milk were collected from different buffalo farms in Karachi for gene detection and antibiotic sensitivity evaluation. Among the samples, 44 % were positive for E. coli, confirmed by specific characteristics and biochemical properties. To check the antimicrobial sensitivity of isolates MIC test was carried out using micro broth dilution method. Antibiotic sensitivity tests revealed that out of the 44 isolates, 68 % were resistant to ampicillin, 81 % to tetracycline, 52 % to levofloxacin, 27 % to cefoxitin, and 25 % to ceftriaxone at various concentrations. Additionally, 7 % of the isolates showed resistance to all classes of antibiotics tested. PCR results indicated that 25 % of the total isolates carried the blaCTX-M-1 ESBL gene, while no other types of blaCTX-M, blaSHV, or blaTEM genes were detected. It was discovered that multidrug resistance and the presence of the blaCTX-M-1 ESBL gene in E. coli isolates from mastitis milk pose a significant threat to veterinarians and human clinicians, as they are highly resistant to beta-lactams and other commonly used antibiotics for mastitis treatment.