Prevalence and molecular characterization of multidrug-resistant Escherichia coli O157: H7 from dairy milk in the Peshawar region of Pakistan

This study analyzed raw (unpasteurized) dairy milk samples from farms, milk vendors, and shops in the Peshawar region of Pakistan for the prevalence of pathogenic multidrug-resistant (MDR) Escherichia coli. During August 2018-September 2019, 100 cow ' s milk samples from 10 subregions of the Town-3 district were tested for the prevalence of E. coli and of Shiga toxin-producing serotype O157: H7 using various biochemical, morphological, and molecular tests. MDR was tested using the disc diffusion method, while Shiga toxin and antibiotic resistance genes were identified by polymerase chain reaction. Twenty eight samples contained E. coli, of which six were positive for O157: H7. The O157: H7 isolates had resistances of 16.7% to amoxicillin-clavulanic acid, 66.7% to ampicillin, 66.7% to ceftriaxone, 50.0% to kanamycin, 83.3% to streptomycin, 83.3% to trimethoprim sulfamethoxazole, and 83.3% to vancomycin. All O157: H7 isolates contained the bla(CTXM) resistance gene, three of which also contained the bla(TEM1) and bla(NDM1) resistance genes, and were resistant to six or seven out of the seven antibiotics tested in a disc diffusion assay with 10 mu g or 30 mu g of antibiotic. Our observations are of high concern to public health in Pakistan, so appropriate measures should be implemented to minimize E. coli O157: H7 cross-contamination and infection, including screening for E. coli O157: H7 in foods, equipment, and storage vessels; testing of isolates for antibiotic resistance; implementation of rigorous hygiene protocols in milk production and storage; training of farmers and milk production workers; and education of the public about hygiene and food practices.