摘要：A known toxigenic highly virulent strain of Clostridium difficile was cultivated in various media and the ability of the bacterium to express several known and putative virulence factors investigated. Sonicated cells and culture supernatants were assayed for the following enzymes: chondroitin-4-sulphatase, hyaluronate lyase, collagenase, collagenaselike peptidase, trypsin, subtilisin, kallikrein and dipeptidyl peptidase. Culture supernatants were further tested for any cytopathic effect and haemagglutination activity. Capsule and fimbriae presence was investigated using electron microscopy on cells grown on solidified media. Expression of these known and putative virulence factors was depressed following growth in nutritionally limited media. The addition of peptide-rich protein hydrolysates to such media reversed this trend. Iron limitation had no stimulatory effect. These data suggest that competition for nutrients within the gut may explain, in part, the poor ability of C. difficile to colonise in the presence ofa normal flora. Furthermore, it is possible that the availability of specific nutrients may affect the expression of certain virulence determinants.Keywords: C. difficile; Virulence expression; Iron limitation; Nutritional requirements.
