Isolation and characterization of enterohaemorragic escherichia coli o157:H7 and ehec o157:NM from raw bovine, camel, water buffalo, caprine and ovine milk in Iran

Abstract

This study was conducted to determine the prevalence rate, virulence genes, and antimicrobial resistance of Escherichia coli O157:H7/NM isolated from dairy bovine, ovine, caprine, camel, and water buffalo milk in Iran. From August 2010 to August 2011, a total of 734 raw milk samples from bovine (192), camel (87), water buffalo (109), caprine (208), and ovine (138) were collected from 269 randomly selected herds in four provinces, Iran and they were evaluated for the presence of Escherichia coli O157:H7/NM using microbiological culture and PCR. Overall, 17 of 734 raw milk samples (2.3%) were found to be contaminated with E. coli O157. The highest prevalence of E. coli O157 was found in water buffalo milk samples (5.5%), followed by bovine (3.6%), ovine (1.4%) and caprine (1.0%). E. coli O157 was not isolated from any of camel milk samples. Of 17 E. coli O157 isolates, 3 were serotype O157:H7 and 14 were serotype O157:NM. All of the 3 E. coli O157:H7 isolates were positive for stx1, stx2, eae A and ehly A genes. The results of this study show that milk from bovine and water buffalo could be a significant source of enterohaemorrahagic E. coli O157:H7 and EHEC O157:NM serotypes in Iran.