Prevalence of potentially pathogenic and antimicrobial-resistant Escherichia coli in raw milk and dairy products in Egypt

Milk and dairy products are popular in Egyptian diets, but their contamination with Escherichia coli, poses health risks. This study investigated the prevalence of potentially pathogenic and antimicrobial-resistant E. coli in raw milk and dairy products from Kafrelsheikh and Algarbia Governorates, Egypt. Two hundred ten samples including raw buffalo milk, goat milk, Domiati cheese, Domiati cheese with pepper, rayeb, and yogurt were analyzed. The prevalence of E. coli was 26.2%, with the highest occurrence in buffalo milk (68.0%) and the lowest in rayeb (7.5%). Based on ERIC-PCR, eighty-four non-clonal E. coli strains were selected and further characterized. Among tested virulence genes, adhesion genes such as lpfAO113 and ehaA, were the most prevalent. Toxin-encoding genes such as astA, cdt, cnf, and hlyA were also detected. The cytotoxic and hemolytic activity of cdt, cnf, and hylA carrying E. coli were confirmed on CHO cells and sheep blood agar, respectively. Twenty-three (27.4%) strains showed resistance to one or more antimicrobials, and 10 (11.9%) strains exhibited multidrug resistance (MDR). Among 12 antimicrobials tested resistance against ampicillin, streptomycin and tetracycline was the highest. Phylogenetic analysis and O-genotyping indicated clinically significant strains such as Og103, Og157 and OgGp9. Notably, two OgGp9 strains were OgGp9:Hg18 and phylogenetic group D, like those associated with a large diarrheal outbreak caused by milk consumption in Japan, in 2021. Interestingly, these two strains harbored a complete type 3 secretion system 2 locus (ETT2) and one of these strains was MDR. These findings indicate that these dairy products were contaminated with potentially pathogenic and multidrug-resistant E. coli. This is the first report to analyze E. coli contamination in Domiati cheese with pepper and detect OgGp9:Hg18 outbreak-associated strains with ETT2 and MDR in Egypt.