Isolation and genomic characterization of Escherichia coli O157:NM and Escherichia coli O157:H7 in minced meat and some traditional dairy products in Iran

Abstract

Human diseases caused by Escherichia coli O157:NM and E. coli O157:H7 strains have been reported throughout the world. In developed countries, serotype O157:H7 represents the major cause of human diseases; however, there have been increasing reports of non-O157 Shiga toxin (Stx)-producing E. coli strains associated with gastrointestinal infections. The present study was conducted to investigate the presence of E. coli O157 and E. coli O157: H7 strains and the presence of virulence genes stx1, stx2, eaeA and ehlyA insolates derived from some traditional dairy products and minced beef meat. A total number of 201 samples including 50 samples from traditional butter, 50 samples from traditional cream, 35 samples from kashk, 30 samples from doogh and 36 samples from minced beef meat were purchased in different supermarkets and retailer shops in Isfahan, Chaharmahal, Bakhtyari and Khuzestan provinces in Iran, over a period of 11-month from August 2010 to May 2011. E. coli non- O157, E. coli O157:NM and E. coli O157:H7 were isolated from 14 samples (7%), 3 samples (1.5%) and 1 sample (out of 50 samples of traditional butter) (0.5%) of the 201 dairy products, respectively, in this study. All the E. coli O157:H7/NM isolates were positive for eaeA and stx1 and/or stx2, and one E. coli O157:H7 isolate was positive for EhlyA. Of the 3 stx positive isolates, 1 and 2 isolates had stx1 and stx2, respectively. To our knowledge, the present study is the first report on isolation and identification of E. coli O157 from traditional butter and cream samples in Iran.

Key words: Escherichia coli O157, butter, cream, traditional dairy products, minced beef meat, Iran.