Etiologic analysis on enterohemorrhagic Escherichia coli O157∶H7 from an infection case in Shanghai

ObjectiveTo understand the etiologic characteristics of an infection case of enterohemorrhagic Escherichia coli (EHEC) O157∶H7 in June, 2016 in Shanghai.

MethodsThe patient information was collected by epidemiological investigation. Two strains were isolated from case's stool samples and identified by biochemical analysis and serologic tests. Polymerase chain reaction was conducted to detect the virulence related genes and microdilution broth method was used to analyze the antibiotic resistance. Pulsed-field gel electrophoresis (PFGE), multi-locus sequence typing (MLST) and single nucleotide polymorphisms (SNP) were conducted for further analysis on the strain's characteristics.

ResultsNo suspected sources of infection were found by epidemiological investigation. The strains were confirmed to be EHEC O157∶H7 carrying eae and stx2, and they were sensitive to 16 kinds of antibiotics tested. Two strains were classified to ST11 while showed a new PFGE pattern. Compared with the reference strain, they showed more SNPs than the previously identified strains by core genome alignment.

ConclusionNo EHEC O157∶H7 has been isolated from patient for about ten years in Shanghai since 2006. The virulence related genes, the antibiotic resistance and the ST type of the strains were confirmed in this study. They were more different from the previously identified strains according to the genome sequence alignment and PFGE results, further attention should be paid to it.