Molecular Studies on Some Emerging Pathogens in Dairy Products Retailed in Dakahlia Governorate, Egypt

In this study, one hundred and ten samples (25 raw buffalo milk, 25 kareish cheese, 25 small-scale yoghurt, and 35 small-scale ice cream) were collected randomly from local markets, dairy shops, and supermarkets from different localities in Dakahlia Governorate, Egypt during October 2019 to March 2020. The prevalence rates of foodborne pathogens including E. coli, Salmonella spp., and Aeromonas hydrophila (A. hydrophila) were examined. Molecular confirmation and detection of toxin-producing and drug-resistance-related genes were carried out using PCR. E. coli was isolated from the examined raw milk, ice cream, Kareish cheese, and yoghurt at 72%, 25.71%, 40%, and 44%, respectively, while Salmonella spp. was isolated at 36%, 4%, and 24% from the examined raw milk, Kareish cheese, and yoghurt samples, respectively. Aeromonas hydrophila was isolated at 36% from the examined raw milk samples, 8% from Kareish cheese samples, and 76% from the examined yoghurt samples. Twelve out of 98 E. coli isolates, 18 out of 30 Salmonella isolates, and 24 out of 50 A. hydrophila were multidrug-resistant, respectively. The most resistant antibiotics were ceftriaxone and tetracycline. All examined E. coli, Salmonella spp., and A. hydrophila isolates contained blaTEM and TetA(A) resistance genes. 66.7% of the examined E. coli isolates harbored stx1, while stx2 was absent in all examined E. coli isolates. All examined Salmonella spp. isolates contained both stn and avrA virulence genes. All examined A. hydrophila contained the Aerolysin, but just 40% contained the hemolysin virulence genes. Therefore, it is necessary to reduce the excessive usage of antibiotics in dairy farms and to apply strict hygienic measures to inhibit microbial contamination of dairy products intended for human consumption.