Enterotoxin plasmid from Clostridium perfringens is conjugative

Clostridium perfringens enterotoxin is the major virulence factor involved in the pathogenesis of C. perfringens type A food poisoning and several non -food-borne human gastrointestinal illnesses. The enterotoxin gene, cpe, is located on the chromosome of food-poisoning isolates but is found on a lar ge plasmid in non-food-borne gastrointestinal disease isolates and in veter inary isolates. To evaluate whether the cpe plasmid encodes its own conjuga tive transfer, a C, perfringens strain carrying pMRS4969, a plasmid in whic h a 0.4-kb segment internal to the cpe gene had been replaced by the chlora mphenicol resistance gene catP, was used as a donor in matings with several cpe-negative C. perfringens isolates. Chloramphenicol resistance was trans ferred at frequencies ranging from 2.0 x 10(-2) to 4.6 x 10(-4) transconjug ants per donor cell. The transconjugants were characterized by PCR, pulsed- held gel electrophoresis, and Southern hybridization analyses. The results demonstrated that the entire pMRS4969 plasmid had been transferred to the r ecipient strain. Plasmid transfer required cell-to-cell contact and was DNa se resistant, indicating that transfer occurred by a conjugation mechanism. In addition, several fragments of the prototype C, perfringens tetracyclin e resistance plasmid, pCW3, hybridized with pMRS4969, suggesting that pCW3 shares some similarity to pMRS4969. The clinical significance of these find ings is that if conjugative transfer of the cpe plasmid occurred in vivo, i t would have the potential to convert cpe-negative C. perfringens strains i n normal intestinal flora into strains capable of causing gastrointestinal disease.