Prevalence and ERIC−PCR Typing of Enterohemorrhagic Escherichia coli O157 in Meat and Vegetables
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Abstract:
The aim of this study was to investigate the prevalence and genotypic diversity of enterohemorrhagic Escherichia coli O157 (EHEC O157) in meat and vegetables. Food samples were collected randomly from 18 cites in China and processed according to the GB/T 4789.36-2008method with slight modifications. The isolates were identified by duplex PCR targeting the rfbE and fliCH7 genes. The presence of four virulence genes (eae, hlyA, stx1, and stx2) in EHEC O157 was determined by single-PCR. Additionally, enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) was used for molecular typing of EHEC O157 isolates. The results showed that 18 (4.35%) of 414 samples were positive for EHEC O157, including 12 fresh meat samples and 6 frozen meat samples. None of the vegetable samples was positive. Furthermore, a total of 52 isolates were identified as EHEC O157 by serotyping, biochemical tests, and duplex-PCR, of which 29 strains were O157:H7, 3strains were O157:NM (carried fliCH7 gene, non-mobile), 2 strains were O157:NM (without fliCH7 gene, non-mobile), and 18strains were O157:hund (undetermined H type). The distribution of virulence genes indicated that 50 out of 52 EHEC O157 isolates carried at least one virulence gene,40 (76.92%) isolates possessed eae gene, 31(59.62%) isolates harbored hlyA gene, 20 (38.46%) isolates harbored stx1 gene, while 24 (46.15%) isolates harbored stx2 gene. ERIC-PCR molecular fingerprint clustering analysis showed that, when the similarity coefficient was 0.80, the strains could be divided into 12 types, and F type was the dominant gene type, indicating a high diversity of genes in these isolates.
