Intra-species growth-inhibition by Clostridium perfringens is a possible virulence trait in necrotic enteritis in broilers

Necrotic enteritis in broiler chickens is associated with Clostridium perfringens type A, carrying the NetB toxin. C. perfringens type A is also a member of the normal intestinal microbiota of broilers. Clinically healthy chickens carry several different C. perfringens clones in their intestine. In flocks suffering from necrotic enteritis, however, mostly only one single clone is isolated from the gut of all the diseased animals. Selective proliferation of these clinical outbreak strains in the gut and spread within the flock seems likely, but an explanation has not yet been given. The hypothesis that necrotic enteritis associated C. perfringens strains might suppress the growth of normal microbiota C. perfringens strains, was therefore tested. Twenty-six C. perfringens strains isolated from healthy broilers and 24 clinical outbreak isolates were evaluated for their ability to induce intra-species growth-inhibition in an in vitro setup. A significantly higher proportion of the C. perfringens clinical outbreak strains inhibited the growth of other C. perfringens strains compared to C. perfringens strains isolated from the gut of healthy chickens. It is proposed that, in addition to toxin production, intra-species growth-inhibition may be a virulence trait that contributes to the ability of certain C. perfringens strains to cause necrotic enteritis in broilers.