Prevalence and Virulence Genes of Escherichia coli O157:H7/NM Isolated from the Feces of Water Buffaloes, Camels, Cattle, Sheep and Goats in Iran

The prevalence of Escherichia coli O157:H7/NM was investigated in 327 fecal samples collected from apparently healthy water buffaloes (43), camels (40), cattle (103), sheep (86), and goats (55) in Isfahan, Chaharmahal & Bakhtyari, and Khuzestan provinces of Iran, between August 2010 and February 2011. Overall, 25 of 327 fecal samples (7.6%) were found to be contaminated with E. coli O157. The highest prevalence of E. coli O157 was found in the water buffalo (18.6%), followed by cattle (11.7%), sheep (4.7%), and the goat (1.8%). E. coli O157 was not isolated from camel fecal samples. Of 25 E. coli O157 isolates, 7 were serotype O157:H7 and 18 were serotype O157:NM. Five of the O157:H7 were isolated from the water buffalo and 2 were from cattle feces. All of the E. coli O157:H7 isolates were positive for eaeA, ehlyA and stx1 and stx2, except one isolate that was ehlyA negative. The highest prevalence of E. coli O157 occurred in summer (16.7%) followed by fall (6.3%). The results of this study show that cattle and buffaloes can be a significant source of human infection with enterohemorrhagic E. coli O157 serotype in Iran. Key words: Escherichia coli O157, feces, ruminant, virulence genes