Acidification-dependent suppression ofC. difficileby enterococci in vitro

Abstract

AbstractClostridioides difficileand Vancomycin-resistantEnterococcus faecium(VRE) are commonly co-isolated from hospitalized patients. We sought to developin vitroco-culture systems to identify interactions and study biofilm formation by these two opportunistic pathogens. We found that VRE quickly acidifies media containing glucose, fructose and trehalose to a pH that is not compatible with growth ofC. difficile. Acidification was necessary and sufficient for VRE-mediated suppression ofC. difficileand this mechanism is conserved among a panel of enterococci andClostridia. Robust co-culture conditions and biofilm formation were achieved by managing the available carbon source.ImportanceThe steady state pH of the colon in humans and mice is below the growth limiting pH forC. difficilefound in this study and others. Following treatment with antibiotics, pH of the colon rises to neutral or slightly alkaline, which correlates with the loss of colonization resistance toC. difficile. These data suggest that manipulation of pH by managing the available carbon source may affect colonization by pathogenic and commensalClostridioides.