This study was undertaken to examine the genetic diversity of Clostridium perfringens isolated from a single broiler flock reared without in-feed antimicrobials (antibacterial growth promoters and anticoccidials) and affected by mild necrotic enteritis (NE). We used pulsed-field gel electrophoresis (PFGE) to investigate the genetic diversity of C. perfringens isolates from broilers of varying disease status, and from litter. The prevalence of the toxin gene netB was also investigated. Altogether 32 PFGE genotypes were found among 88 isolates. Several genotypes were detected in C. perfringens-associated organ lesions from chickens that were sampled at random and alive without clinical symptoms, suggesting that these genotypes proliferated concurrently in such lesions. More than 90% of all isolates from NE-specific organ lesions carried netB which codes for a recently described pore-forming toxin. NetB positive isolates were less predominant in non-lesion samples from broilers affected by NE, and found infrequently or not at all in healthy birds and isolates from litter. These findings show that the presence of netB in C. perfringens strains is associated with NE and suggest that mild NE differs from severe NE with regard to C. perfringens genotype diversity.
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