Question

Shiga toxin-producing E. coli (STEC), including the subgroup of enterohemorrhagic E. coli (EHEC), are important bacterial pathogens which cause diarrhea and the severe clinical manifestation hemolytic uremic syndrome (HUS). Genomic surveillance of STEC/EHEC is a state-of-the-art tool to identify infection clusters and to extract markers of circulating clinical strains, such as their virulence and resistance profile for risk assessment and implementation of infection prevention measures. The aim of the study was characterization of the clinical STEC population in Germany to establish a reference data set for STEC/EHEC molecular surveillance and detection of infection clusters.

Methods

From 2020 to 2022 1,257 STEC isolates, including 39 of known HUS association, were analyzed by PCR-based virulence gene analysis, antibiotic susceptibility testing and whole genome sequencing including bioinformatic analysis.

Results

Major serogroups in all clinical STEC analyzed were O26, O146, O91, O157, O103, and O145; and in HUS-associated strains were O26, O145, O157, O111, and O80. stx1 was less frequently and stx2 or a combination of stx, eaeA and ehxA were more frequently found in HUS-associated strains. Predominant stx gene subtypes in all STEC strains were stx1a (24 %) and stx2a (21%) and in HUS-associated strains were mainly stx2a (69%) and the combination of stx1a and stx2a (12.8%). Furthermore, two novel O-antigen gene clusters (RKI6 and RKI7) and strains of serovars O45:H2 and O80:H2 showing multidrug resistance were detected. By means of phylogenetic analysis, 383 isolates (30.4%) were assigned to 129 infection clusters (threshold allelic distance > 10 AD) including two to ten isolates.

Conclusions

The implemented surveillance tools now allow to comprehensively define the population of clinical STEC strains including those associated with the severe disease manifestation HUS reaching a new surveillance level in Germany. Therefore, the integration of epidemiological data and data of the competent food authorities on national and international level leads to highly efficient control strategies positively impacting public health.