The interactions between the gut microbiota and pathogens are complex and can determine the outcome of an infection. Enterohemorrhagic Escherichia coli (EHEC) is a major human enteric pathogen that colonizes the colon through attaching and effacing (AE) lesions and uses microbiota-derived molecules as cues to control its virulence. Different gut commensals can modulate EHEC virulence. However, the lack of an animal model that recapitulates the human pathophysiology of EHEC infection makes it challenging to investigate how variations in microbiota composition could affect host susceptibility to this pathogen. Here, we addressed these interactions building from simple to more complex in vitro systems, culminating with the use of the physiological relevant human colonoids as a model to study the interactions between EHEC and different gut commensals. We demonstrated that Bacteroides thetaiotaomicron and Enterococcus faecalis enhance virulence expression and AE lesion formation in cultured epithelial cells, as well as on the colonic epithelium, while commensal E. coli did not affect these phenotypes. Importantly, in the presence of these three commensals together, virulence and AE lesion are enhanced. Moreover, we identified specific changes in the metabolic landscape promoted by different members of the gut microbiota and showed that soluble factors released by E. faecalis can increase EHEC virulence gene expression. Our study highlights the importance of interspecies bacterial interactions and chemical exchange in the modulation of EHEC virulence. IMPORTANCE Enterohemorrhagic E. coli (EHEC) is a natural human pathogen that poorly colonizes mice. Hence, the use of murine models to understand features of EHEC infection is a challenge. In this study, we use human colonoids as a physiologically relevant model to study interactions between EHEC and gut commensals. We demonstrate that the ability of EHEC to form AE lesions on the intestinal epithelium is enhanced by the presence of certain gut commensals, such as B. thetaiotaomicron and E. faecalis, while it is not affected by commensal E. coli. Furthermore, we show that commensal bacteria differently impact the metabolic landscape. These data suggest that microbiota compositions can differentially modulate EHEC-mediated disease.
Keywords: EHEC; exometabolome; gut microbiota composition; human colonoids; virulence regulation.