Genome-wide association study of hemolytic uremic syndrome causing Shiga toxin-producing Escherichia coli from Sweden, 1994-2018

Epidemiological Characteristics of Shiga Toxin-Producing Escherichia coli Responsible for Infections in the Polish Pediatric Population

Shiga toxin-producing Escherichia coli (STEC) are zoonotic pathogens causing hemorrhagic colitis and hemolytic uremic syndrome (HUS) in children and the elderly. Stool samples were collected from 180 children hospitalized in five pediatric centers in Poland in 2018-2022. Direct stx1/stx2 gene detection by PCR in feces and E. coli isolates was performed. Antibiotic susceptibility was tested according to EUCAST v.12. Randomly selected isolates were serotyped with O157 antiserum and genotyped by pulsed-field gel electrophoresis (PFGE). A total of 44 E. coli isolates were confirmed as STEC by PCR. Among them, 84.4% were positive for stx2, and equally 6,8% for only stx1 and both stx1 and stx2 genes. The stx1 gene was also found in one Citrobacter freundii isolate. E. coli serotype O157 was present in 97.6% of the isolates. STEC infections most often occurred between June-October with a peak in July and August (51%). The highest, 77.8% of STEC isolates were found in the 1-5 years old group. No extended-spectrum β-lactamases (ESBL) were found. Resistance only to amoxicillin/clavulanic acid (24.4%), piperacillin/tazobactam (3%), cefotaxime (6%), gentamicin (6%), ciprofloxacin (3%), azithromycin (3%), trimethoprim/sulfamethoxazole (24,2%) was detected. PFGE analysis showed 18 PFGE types with no clonal distribution. Eight isolates with A, B, and C PFGE types showed genetic relatedness in the type with no detection of transmission way of distribution. STEC strains pose a serious threat to human health, therefore demographic and epidemiological characteristics are crucial for their surveillance.

Genomic surveillance of STEC/EHEC infections in Germany 2020 to 2022 permits insight into virulence gene profiles and novel O-antigen gene clusters

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 for establishment of a reference data set. To that end, from 2020 to 2022 1257 STEC isolates, including 39 of known HUS association, were analyzed and lead to a classification of 30.4 % into 129 infection clusters. 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. In conclusion, 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.

Complex effects of the exo-xis region of the Shiga toxin-converting bacteriophage Φ24B genome on the phage development and the Escherichia coli host physiology

Lambdoid bacteriophages are excellent models in studies on molecular aspects of virus-host interactions. However, some of them carry genes encoding toxins which are responsible for virulence of pathogenic strains of bacteria. Shiga toxin-converting bacteriophages (Stx phages) encode Shiga toxins that cause virulence of enterohemorrhagic Escherichia coli (EHEC), and their effective production depends on Stx prophage induction. The exo-xis region of the lambdoid phage genome consists of genes which are dispensable for the phage multiplication under laboratory conditions; however, they might modulate the virus development. Nevertheless, their exact effects on the phage and host physiology remained unclear. Here, we present results of complex studies on the role of the exo-xis region of bacteriophage Φ24B, one of Stx2b phages. Transcriptomic analyses, together with proteomic and metabolomic studies, provided the basis for understanding the functions of the exo-xis region. Genes from this region promoted lytic development of the phage over lysogenization. Moreover, expression of the host genes coding for DnaK, DnaJ, GrpE, and GroELS chaperones was impaired in the cells infected with the Δexo-xis phage mutant, relative to the wild-type virus, corroborating the conclusion about lytic development promotion by the exo-xis region. Proteomic and metabolomic analyses indicated also modulation of gad and nrf operons, and levels of amino acids and acylcarnitines, respectively. In conclusion, the exo-xis region controls phage propagation and host metabolism by influencing expression of different phage and bacterial genes, directing the virus to the lytic rather than lysogenic developmental mode.