Molecular characterisation and stress tolerance ofEscherichia coliisolated from dairy and dried milk-related products

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This study characterised the phylogenetic groups, pathotypes, antibiotic resistance and stress response of Escherichia coli isolates recovered from dairy and dried milk-related products. A total of 54 isolates of E. coli were recovered from thirty-three of 180 samples (18%) of these products. Representatives from all the four phylogenetic groups of the organism were identified, although groups A and B1 dominated groups B2 and D. Enterotoxigenic E. coli (ETEC) strains producing heat-labile toxin (LT) could be detected among the isolates and were found to be associated with the Kariesh cheese. Escherichia coli isolates showed single-drug and multiple-drug resistance to ß-lactams and other antibiotic classes. The blaTEM-1 gene was found to be associated with resistance to ampicillin but not to cephalothin. Escherichia coli survived heating at 50 and 55 °C for 60 min, but was undetectable after only 10 min of exposure to 60 °C. It also survived in the presence of 6% and 8% salt for 96 h and in pH 4.0 for 72 h.


An agarose gel showing the results of a triplex PCR analysis of the different phylogenetic groups of E. coli isolated from dairy and dried milk-related products.

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