Study on biological characteristics of Shiga toxin-producing Escherichia coli O157:H7 from different sources

Objective The present study was conducted to find out the pulsed field gel electrophoresis (PFGE) patterns, virulence genes and drug resistance of Shiga toxin-producing Escherichia coli (STEC O157:H7) in Zhejiang Province. Methods The biochemistry and the serotype of STEC O157:H7 was identified by the API 20E identification system and slide agglutination test with diagnostic antiserum specific for O157:H7, respectively. O antigen, H7 antigen of suspicious STEC O157:H7 and its virulence genes, including stxl, stx2, hly and eae, were examined by routine PCR.The pulse field gel electrophoresis(PFGE) was used to analyze the pattern of the genomic DNA, digested by Xba1. Antimicrobial susceptibility tests were performed with 14 antibiotics by K-B test. Results 5 suspicious strains were identified as STEC O157:H7 with biochemical and serological test. PCR results shows that SLT2, hly and eaeA were positive and SLT1 was negative. There were 4 PFGE patterns of the 5 STEC O157:H7 strains. The PFGE patterns of 2 Jinghua isolates were homologous and that of the other 3 strains were apparently different. Analysis on drug-resistance shows the isolates were susceptible to Cefalotin, Claforan, Gentamicin, and Ciprofloxacin(100%), but resistant to co-trimoxazole and Ampcillin(100%). Conclusion In some regions in Zhejiang Province there exists STEC O157:H7 with the virulence gene SLT2, which takes on multiple PFGE patterns. Transmission of the infection among human beings may be likely to occur, and surveillance on O157:H7 should be taken seriously to prevent the bacteria from being transmitted among human beings.