Inactivation of the gene (cpe) encoding Clostridium perfringens enterotoxin eliminates the ability of two cpe-positive C-perfringens type A human gastrointestinal disease isolates to affect rabbit ileal loops

Previous epidemiological studies have implicated Clostridium perfringens enterotoxin (CPE) as a virulence factor in the pathogenesis of several gastrointestinal (GI) illnesses caused by C. perfringens type A isolates, including C. perfringens type A food poisoning and non-food-borne GI illnesses, such as antibiotic-associated diarrhoea and sporadic diarrhoea. To further evaluate the importance of CPE in the pathogenesis of these GI diseases, allelic exchange was used to construct cpe knock-out mutants in both SM101 (a derivative of a C. perfringens type A food poisoning isolate carrying a chromosomal cpe gene) and F4969 (a C. perfringens type A non-food-borne GI disease isolate carrying a plasmid-borne ope gene). Western blot analyses confirmed that neither ope knockout mutant could express CPE during either sporulation or vegetative growth, and that this lack of CPE expression could be complemented by transforming these mutants with a recombinant plasmid carrying the wild-type ope gene. When the virulence of the wild-type, mutant and complementing strains were compared in a rabbit ileal loop model, sporulating (but not vegetative) culture lysates of the wild-type isolates induced significant ileal loop fluid accumulation and intestinal histopathological damage, but neither sporulating nor vegetative culture lysates of the ope knock-out mutants induced these intestinal effects. However, full sporulation-associated virulence could be restored by complementing these ope knock-out mutants with a recombinant plasmid carrying the wildtype ope gene, which confirms that the observed loss of virulence for the ope knock-out mutants results from the specific inactivation of the ope gene and the resultant loss of CPE expression. Therefore, in vivo analysis of our isogenic ope mutants indicates that CPE expression is necessary for these two cpe-positive C. perfringens type A human disease isolates to cause GI effects in the culture lysate:ileal loop model system, a finding that supports CPE as an important virulence factor in GI diseases involving ope-positive C. perfringens type A isolates.