Genotypic Identification of Extended spectrum ?-lactamase producing Escherichia coli in dairy supply chain

Abstract

Foodborne illnesses due to antibiotic-resistantbacteria represents a major public health problem in bothdeveloped and developing countries. Among 190 samples, 139Escherichia coli positive isolates from raw milk, pasteurized milk,and human handlers were identified by phenotypic methods andgenotypic methods. All E. coli isolates were found to beresistance to penicillin, oxacillin, erythromycin and clindamycin.The dominant type of resistance to cefotaxime and amoxiclaveidentically detected in 18.7% isolates followed by ampicillin in17.98%, trimethoprim 15.82%, tetracycline 10.79%, nalidixic acid7.91%, and piperacillin 7.79%. Four isolates have shown resistance(2.87%) to Ceftriaxone and ceftazodime, Cefotaxime and one isolatehas shown resistance to Cefepime. Further, all four isolates wereconfirmed as extended spectrum ?-lactamase (ESBL) producerby double disc diffusion test and ESBL chromogenic medium.Later, all four isolates were evaluated by PCR and they areobserved as carrier of blaCTX M gene which is responsible forESBL antibiotic resistance in E.coli but blaTEM and blaSHVgenes were absent in all four ESBL isolates. Based on the abovefindings, it is concluded that ESBL antibiotic resistance in E. coliwere more prevalent in milk and this may due to spread andacquirement of antibiotics resistance gene by plasmid and mobilegenetic elements