Clostridium difficile adherence to mucus: Results of an in vivo and ex vivo assay

The ability to associate with mucus constitutes an important virulence factor in some bacteria. We took advantage of two experimental models to study adhesion to, or association with, the caecal mucus of axenic mice by Clostridium difficile strains representing various serogroups and of differing origins and toxigenicity. In vivo, the axenic mice were tube-fed with various clostridial strains: followed by enumeration of adherent bacteria to the rinsed caecum. The results obtained in vivo were compared with those obtained with an ex vivo experimental model: adherent clostridia to a turned-over caecum were enumerated after the caecum was excised in an anaerobic chamber, leaving the mucus layer in situ. The results showed good reproductivity between the in vivo and ex vivo models for the majority of strains. In vivo, toxigenic strains adhered better to the mucus than non toxigenic strains, suggesting that the toxins may promote C. difficile adherence to mucus. Although C. difficile was correctly implanted and multiplied in the murine digestive tract, it is unclear if this represents specific adhesion to receptors present in the caecal mucus or an association only.