Toxigenicity and adherence in Clostridium difficile strains isolated from patients with and without diarrhoea.

The mechanisms by which Clostridium difficile causes diarrhoea are unknown. The expression of putative virulence factors by 44 Clostridium difficile strains isolated from patients with and without diarrhoea was studied. Toxins A and B were tested in CHO and MRC-5 cells, respectively; adherence was measured in two substrates: HEp-2 cells and polystyrene plates. The in vitro expression of toxins A and B by strains isolated from patients with diarrhoea was not significantly different from that by strains isolated from patients without diarrhoea. The ability of adherence to both HEp-2 cells and polystyrene by strains isolated from patients with diarrhoea was not significantly different when compared with strains isolated from patients without diarrhoea; however, strains isolated from adults with diarrhoea seem to adhere to a greater extent to both substrates than strains isolated from adults without diarrhoea. Twenty three strains which did not produce toxins A and B were tested for enterotoxicity in rat small intestine. Eight such strains induced fluid accumulation and seven of them were isolated from children. Adherence to cells and to polystyrene might be an important virulence factor in strains causing diarrhoea in adults; whereas the production of toxins other than A and B might be an important pathogenic mechanism in strains causing diarrhoea in children.