Characterization of Urinary Tract Infection-Associated Shiga Toxin-Producing Escherichia coli

Abstract

c Enterohemorrhagic Escherichia coli (EHEC), a subgroup of Shiga toxin (Stx)-producing E. coli (STEC), is a leading cause of diarrhea and hemolytic-uremic syndrome (HUS) in humans. However, urinary tract infections (UTIs) caused by this microorganism but not associated with diarrhea have occasionally been reported. We geno-and phenotypically characterized three EHEC isolates obtained from the urine of hospitalized patients suffering from UTIs. These isolates carried typical EHEC virulence markers and belonged to HUS-associated E. coli (HUSEC) clones, but they lacked virulence markers typical of uropathogenic E. coli. One isolate exhibited a localized adherence (LA)-like pattern on T24 urinary bladder epithelial cells. Since the glycosphingolipids (GSLs) globotriaosylceramide (Gb3Cer) and globotetraosylceramide (Gb4Cer) are well-known receptors for Stx but also for P fimbriae, a major virulence factor of extraintestinal pathogenic E. coli (ExPEC), the expression of Gb3Cer and Gb4Cer by T24 cells and in murine urinary bladder tissue was examined by thin-layer chromatography and mass spectrometry. We provide data indicating that Stxs released by the EHEC isolates bind to Gb3Cer and Gb4Cer isolated from T24 cells, which were susceptible to Stx. All three EHEC isolates expressed stx genes upon growth in urine. Two strains were able to cause UTI in a murine infection model and could not be outcompeted in urine in vitro by typical uropathogenic E. coli isolates. Our results indicate that despite the lack of ExPEC virulence markers, EHEC variants may exhibit in certain suitable hosts, e.g., in hospital patients, a uropathogenic potential. The contribution of EHEC virulence factors to uropathogenesis remains to be further investigated. Escherichia coli is one of the most versatile microorganisms that rapidly colonizes the gastrointestinal tract of newborns (1). Although E. coli usually represents an important commensal of the normal intestinal microbiota, other variants that are able to cause infections exist (1, 2). On the basis of their virulence properties and the site of infection, these bacteria are classified as intestinal pathogenic E. coli (IPEC), which are associated with diarrhea, and extraintestinal pathogenic E. coli (ExPEC), which cause infections beyond the intestinal tract (3). Enterohemorrhagic E. coli (EHEC) belongs to the IPEC group of bacteria and represents one of the main causative agents of diarrhea, hemorrhagic colitis (HC), and hemolytic-uremic syndrome (HUS) in humans (4). The characteristic main EHEC virulence markers include the locus of enterocyte effacement (LEE) pathogenicity island and Shiga toxin (Stx)-encoding bacteriophages. Additionally, other toxins, including the cytolethal distending toxin (CDT), EHEC hemolysin (Hly), serine protease EspP, subtilase cytotoxin, cyclomodulin Cif, and different siderophore systems, as well as adhesins can also contribute to EHEC pathogenesis (5). These EHEC virulence factors are absent from archetypal ExPEC strains.Similarly, the main ExPEC virulence fa...

Intracellular d -Serine Accumulation Promotes Genetic Diversity via Modulated Induction of RecA in Enterohemorrhagic Escherichia coli

“…EHEC isolates, while attracted specifically to the distal colon, have the capacity to at least come into contact with the urinary tract and, in some rare cases, have even been associated with urinary tract infections (69). Our data suggest, however, that in these cases, high concentrations of D-serine would not be a driver of stx expression and that other unknown factors contribute to this rare phenomenon.…”

A Novel Protective Vaccine Antigen from the Core Escherichia coli Genome

“…It contains the ST678 EAHEC strains involved in the 2011 German outbreak (1, 13–15) and strains from progenitor EHEC and EAEC STs that contributed to the emergence of this highly virulent lineage (e.g., the EAEC strain 55989 and the EHEC strains 2009EL-2050 and 2009EL-2071). Interestingly, phylogroup AxB1 is also represented by ST675, recently described as containing EHEC strains involved in UTI cases (16). Moreover, this group also contains nonpathogenic strains and strains from APEC and ETEC pathotypes.…”

Shiga toxin glycosphingolipid receptors of Vero-B4 kidney epithelial cells and their membrane microdomain lipid environment

“…TLC analysis and corresponding overlay binding assays revealed the presence of Gb3Cer, the major Stx receptor, and Gb4Cer, the less effi cient receptor, in Vero cells. Heterogeneity regarding TLC separation was observed in several previous studies and orcinol as well as Stx-detected bands of receptor GSLs suggested ceramide heterogeneity owing to fatty acids with varying acyl chain lengths ( 14,15,20,23 ). We provide here the full structural elucidation of Stx receptors of Vero-B4 cells and identifi ed Gb3Cer (d18:1, C24:0/C24:1) and Gb3Cer (d18:1, C16:0) as the prevalent Gb3Cer species (see Table 1 ), as well as similar variability for the corresponding prevalent Gb4Cer species.…”

“…Since this discovery, numerous studies have shown the functional impact of globo-series GSLs as Stx-specifi c receptors and their key role regarding toxin-mediated cytotoxicity in Vero cells ( 14,15,18,20,22,23,83 ). TLC analysis and corresponding overlay binding assays revealed the presence of Gb3Cer, the major Stx receptor, and Gb4Cer, the less effi cient receptor, in Vero cells.…”