ABSTRACT
Objective:To understand the molecular characteristics of Escherichia coli producing Shiga toxin 2e subtype isolated from different sources in China. Methods:Three human-derived, 13 animal-derived and eight food-derived stx2e-positive Escherichia coli strains which were isolated during 2012 to 2018 were analyzed by antimicrobial susceptibility testing and whole genome sequencing. The stx subtype, serotype, multi-locus sequence type, virulence genes and antimicrobial resistance genes of each strain were determined by whole genome sequences. The phylogenetic relationship and genetic composition of Shiga-toxin prophage were explored. Results:Twenty-four stx2e-STEC strains were typed into 19 O∶H serotypes and 19 sequence types (STs). Each strain carried at least one kind of antimicrobial resistance gene and 19 out of 24 strains were resistant to at least one kind of antimicrobials. Three human-derived strains were heterogenous in serotypes and STs, but there were several animal and food-derived strains shared the same serotype or ST with human strains and showed close relationship in the phylogenetic analysis. The sequences of stx2e among all strains were highly conserved (similarity >99.7%), but there were significant differences in the size and the gene composition of Shiga toxin prophage genome. Conclusions:This is report about the characteristics of rare human-derived Stx2e-STEC strains in China. Comparing human isolates with animal-and food-derived strains, it indicates that Stx2e-STEC strains are highly genetic diversity and have the potential to infect humans.
ABSTRACT
Objective:To investigate the prevalence and molecular characteristics of Escherichia coli ( E. coli) producing a novel Shiga toxin 2k subtype in goat in Lanling county, Shandong province. Methods:In November 2019, 512 goat fecal samples were collected from different households in Lanling county, Shandong province. After enriched with EC broth, stx-positive samples were detected by PCR and inoculated in CHROMagar? ECC agar and CHROMagar? STEC agar. The whole genomes of stx-positive strains were sequenced. Based on the genomic senquences, the stx subtype, serotype, multi-locus sequence type and virulence genes of each strain were analyzed. Results:Eighty-six strains of Shiga toxin-producing E. coli (STEC) were isolated from 512 goat fecal samples. Five stx subtypes were identified and 37 strains were positive for stx2k. The 86 STEC strains belonged to 20 O∶H serotypes and 18 different sequence types (STs). Conclusions:STEC strains circulating in goats in Lanling county, Shandong province were heterogeneous in stx subtypes, serotypes and virulence gene profiles, and a certain proportion of strains producing a novel Shiga toxin 2k subtype were detected.