The adherent abilities of Clostridium perfringens strains are critical for the pathogenesis of avian necrotic enteritis

•The cnaA gene is found in necrotic enteritis-causing Clostridium perfringens.•cnaA, the first gene in an operon with four downstream genes, was mutated.•cnaA mutants lost the ability to bind to several collagen types and cause disease.•The mutants had a reduced ability to colonise the chicken intestinal mucosa.•Adherence was shown to be an important property of virulent C. perfringens strains. Necrotic enteritis of poultry is an emerging disease of substantial economic importance, but aspects of the pathogenesis of this multi-factorial disease are still unclear. We recently demonstrated that the ability of avian strains of the causative bacterium, Clostridium perfringens, to bind to specific collagen types correlated strongly with their virulence and we postulated that binding of the pathogen to collagen types IV and V and gelatin may involve the putative adhesin-encoding gene cnaA, which is found in the VR–10B locus. In this study we have used site-directed mutagenesis to demonstrate that disruption of the cnaA gene leads to a reduction in the expression of the three genes immediately downstream of cnaA and reduced adherence to collagen types IV and V and gelatin. In addition, a cnaA mutant of strain EHE-NE18 was no longer capable of causing necrotic enteritis in a chicken disease induction model and had a significantly reduced ability to colonise the chicken intestinal mucosa. These results were confirmed by generating and analysing a similar mutant in an independent necrotic enteritis causing C. perfringens strain. This study expands our understanding of the mechanisms involved in necrotic enteritis pathogenesis by demonstrating the importance of C. perfringens adherence to extracellular matrix proteins.