Objective: To identify suspected Escherichia coli O157 strains collected by national foodborne disease surveillance system from 2005 to 2007, as well as to investigate their virulence gene' s distribution in different kinds of food.
Methods: All suspected strains were primarily tested by biochemical test strips API20E, and typed by agglutination with O/H serum, the virulence genes were detected by PCR.
Results: (1) A total of 154 strains were identitied as Escherichia coli by API20E. (2) A total of 89 strains from 154 suspected strains were identified as Escherichia coli O157 by serotype test and PCR of special gene, of them 42 were O157:H7 (47%) and the rest were O157: NM and O157: hund (3) Virulence genes test by PCR: all of 42 O157: H7 strains and 6 O157: NM strains carried eaeA and hlyA: 28 sorbitol-non fermenting O157: H7 strains carried stx with a total of 29 positive ones. (4) The strains carrying stx gene of E. coli O157: H7 were identified in different groups of food, such as mutton, beef, pork, chicken and salad.
Conclusion: E. coli O157 strains with different virulence genes were isolated from parts of the surveyed food. From now on, research should be carried out to enhance the surveillance of E. coli O157 not only in food but also from environment in order to provide more scientific data for establishing effective measures of protection.