Prevalence of Escherichia coli O۱۵۷:H۷ in bulk milk, northwestern Iran, in ۲۰۲۴

Background: E. coli O۱۵۷:H۷ is a foodborne pathogen. Known for producing Shiga toxin, which causes serious illnesses. Consumption of contaminated food is the most important route of transmission of infection to humans. Among the foods, milk and dairy products are the most important reservoirs. Given its low infectious dose and high public health significance, the present study aims to determine the molecular prevalence of E. coli O۱۵۷:H۷ in bulk milk samples in Ardabil Province during ۲۰۲۴. Methods: Bulk milk samples were collected from livestock (cattle, sheep, and goat) across Ardabil Province. Initially, all samples were subjected to bacterial culture on selective and differential media to isolate E. coli. Suspected colonies were then examined through biochemical gallery tests (including IMViC tests) with a particular focus on MR-VP (Methyl Red–Voges Proskauer) tests for preliminary confirmation of E. coli. DNA was extracted using a kit (sambio DNA reagent, South Korea) according to the manufacturer's protocol. For molecular identification, the PCR method was performed using specific primers to detect the eae gene. Results: In total, ۲۸۱ raw bulk milk samples, including ۱۳۸ from cattle, ۱۱۳ from sheep, and ۳۰ from goats, were collected across ۱۲ counties of Ardabil Province. A total of ۹ samples out of ۲۸۱ were positive for E. coli O۱۵۷:H۷ (۳.۲%), with the highest contamination rate observed in cattle milk (۴.۳%), followed by sheep milk (۲.۶%), while no contamination was detected in goat milk. Geographical distribution showed that the highest level of contamination was observed in Bilehsavar County. Conclusion: The results of this study demonstrated that raw milk can serve as a significant reservoir for E. coli, highlighting the importance of avoiding the consumption of unpasteurized dairy products and the importance of strict health surveillance and continuous monitoring throughout the stages of dairy production and distribution.

کلیدواژه ها:

E. coli O۱۵۷:H۷ ، bulk milk ، PCR ، Ardabil ، livestock ، eae