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stx Genotypes and Virulence Characteristics of E. coli O157:H7 Strains Isolated from Meat Products Commercialized in Wuhan

ZHENG Dong-dong1, BI Wang-lai1, WANG Hong-xun2, LIU Zhi-guo1, DING Hong-bo1, LI Rui1,3,*   

  1. 1. College of Biological and Pharmaceutical Engineering, Wuhan Polytechnic University, Wuhan 430023, China；
    2. College of Food Science and Engineering, Wuhan Polytechnic University, Wuhan 430023, China;
    3. Hubei Collaborative Innovation Center for Processing of Agricultural Products, Wuhan 430023, China
  • Online:2014-04-25 Published:2014-05-13
  • Contact: LI Rui

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Abstract:

A total of 117 raw meat samples were collected from 22 markets in Wuhan, China and four E. coli O157:H7
strains were isolated from these meat samples, which were positive for stx, hly and eae genes. The stx variant genes were
further subtyped by polymerase chain reaction (PCR) using sequence-specific primers targeting each stx variant. Three
isolates were found to carry both stx1 and stx2 genes, and the prevalent stx genotypes were stx1a and stx2a. One isolate EC
5.11 was found to carry only stx2 gene but it could not be subtyped by PCR assay. The entire stx2 gene was then amplified from
EC 5.11, cloned into a vector and sequenced. Sequencing data showed that the stx2 gene of EC5.11 was 100% identical to the
published sequences of stx2c. The production of Shiga toxin from the four isolates was confirmed by Vero cell toxicity assay.

Key words: E. coli O157:H7, Shiga-toxin, stx genotype, Vero cytotoxicity

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