Molecular characteristics of human-derived non-O157 Shiga toxin-producing Escherichia coli strains isolated in five regions of China

Objective To understand the molecular characteristics of human-derived non-O157 Shiga toxin-producing Escherichia coil (STEC) strains circulating in five regions of China. Methods Twenty-seven non-O157 STEC strains isolated in five geographic regions were investigated by serotyping, stx1/stx2 subtyping and PCR screening for adhesion and other virulence genes. A multilocus sequence typing (MLST) scheme provided by E. coil MLST database were performed to amplify and sequence seven housekeeping genes (adk, icd, fumC, rgyrB, purA, mdh and recA) in those strains. Results Twenty-seven non-O157 STEC strains were typed into 16 O∶H serotypes. Among those strains, 11 harbored stx1a, 12 harbored stx1c, two harbored stx2e and the other three strains respectively harbored stx1a+ stx2b, stx2d and stx2g. Positive rates of eae, efa1, saa, paa, toxB, astA and ehxA genes were 18.5%, 18.5%, 29.6%, 22.2%, 11.1%, 11.1% and 25.9%, respectively. The 27 strains were typed into 16 different sequence types (STs) based upon MLST. Conclusion Human-derived non-O157 STEC strains circulating in five regions of China are heterogeneous in their serotypes, stx1/stx2 subtypes and virulence gene profiles. Key words: Non-O157 Shiga toxin-producing Escherichia coli; Shiga toxin; Serotyping; MLST