Abstract
Shiga toxin-producing Escherichia coli (STEC) are important foodborne pathogens that can cause human infections ranging from asymptomatic carriage to bloody diarrhea (BD) and fatal hemolytic uremic syndrome (HUS). However, the molecular mechanism of STEC pathogenesis is not entirely known. Here, we demonstrated a large scale of molecular epidemiology and in-depth genomic study of clinical STEC isolates utilizing clinical and epidemiological data collected in Region Jönköping County, Sweden, over a 15-year period. Out of 184 STEC isolates recovered from distinct patients, 55 were from patients with BD, and 129 were from individuals with non-bloody stools (NBS). Five individuals developed HUS. Adults were more associated with BD. Serotypes O157:H7, O26:H11, O103:H2, O121:H19, and O104:H4 were more often associated with BD. The presence of Shiga toxin-encoding gene subtypes stx2a, stx2a + stx2c, and stx1a + stx2c was associated with BD, while stx1a was associated with milder disease. Multiplex virulence and accessory genes were correlated with BD; these genes encode toxins, adhesion, autotransporters, invasion, and secretion system. A number of antimicrobial resistance (AMR) genes, such as aminoglycoside, aminocoumarin, macrolide, and fluoroquinolone resistance genes, were prevalent among clinical STEC isolates. Whole-genome phylogeny revealed that O157 and non-O157 STEC isolates evolved from distinct lineages with a few exceptions. Isolates from BD showed more tendency to cluster closely. In conclusion, this study unravels molecular trait of clinical STEC strains and identifies genetic factors associated with severe clinical outcomes, which could contribute to management of STEC infections and disease progression if confirmed by further functional validation.
Highlights
Shiga toxin-producing Escherichia coli (STEC) belong to a genetically and phenotypically diverse group of E. coli strains characterized by the production of one or more Shiga toxins (Stx) (Bryan et al, 2015)
The majority of isolates of serotypes O157:H7, O121:H19, and O104:H4 were correlated to bloody diarrhea (BD) (Figure 1)
A whole-genome phylogeny was constructed from alignment of concatenated coding sequences (CDSs) of the 2,485 shared-loci found in all 184 STEC isolates and six Escherichia coli reference genomes representing main STEC serotypes (O157:H7, O145:H28, O111: H, O26:H11, O104:H4, and O103:H2)
Summary
Shiga toxin-producing Escherichia coli (STEC) belong to a genetically and phenotypically diverse group of E. coli strains characterized by the production of one or more Shiga toxins (Stx) (Bryan et al, 2015). It is noteworthy that a previous study estimated that the true annual number of STEC cases in Germany is 28,347, with a median of 4,969 cases due to O157 STEC and 22,019 cases due to non-O157 STEC, which is much higher than the number registered in European surveillance system (Kuehne et al, 2016). This is probably true for many other European countries as well
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