Isolation and Molecular Characterization of Extended Spectrum Beta Lactamase Producing Escherichia coli from Milk

Milk plays a major role as a source of nutrition in the diet but contaminated milk can be a source of harmful bacteria. Escherichia coli is opportunistic pathogen and is responsible for a wide range of infections. The prevalence of pathogenic multi-drug resistant extended-spectrum β-lactamase (ESBL)-producing E. coli is increasing and becoming a global concern. A study was carried out to isolate ESBL producing E. coli from 150 milk samples from Anand and around villages. Total 94(62.66%) samples were found positive as E. coli by isolation on MacConkey and Eosin Methylene Blue agar which were confirmed by primary & biochemical tests including Gram's staining. Antibiotic sensitivity test (ABST) was performed against 6 antibiotics and isolates found resistant to Aztrionem: 58(61%), Cefoxitin: 20(21%), Ceftriaxone: 56(59%), Ceftazidime: 62(65%), Cefpodoxime: 34(44.73%) & Ceftazidime + Clavulanic acid: 8(8.5%). A total 34(36.17%) ESBL producing E. coli were phenotypically confirmed by ABST and Epsilometer test. Genotypic confirmation of 34 isolates was done by PCR and isolates found positive for bla _{CTX M-3} gene: 18(52.94%), bla _{CTX M-9} gene 6(17.64%), bla _SHV gene: 5(14.70%) and bla _TEM gene: 5(14.70%). In summary, analyzed milk samples were found to have a health risk for consumers due to contamination by ESBL producing E. coli, their pathogenicity and treatment failure as a result of antibiotic resistance.