Characterization of Clostridium perfringens recovered from broiler chicken affected by necrotic enteritis.

Necrotic enteritis (NE) caused by Clostridium perfringens has emerged as an important disease associated with major economic losses in the poultry industry worldwide. The ban and voluntary withdraw of antimicrobial growth promoters used to control NE have resulted in resurgence of NE. Moreover, consumer demand for antibiotic free poultry product has continued to grow. The presence of the netB gene encoding for pore forming toxin in C. perfringens has been shown to be essential for pathogenesis of NE. The aim of this study was to characterize C. perfringens isolates recovered from broiler chickens affected by NE. A total of 230 isolates obtained from commercially raised broilers between 3 and 4 wk of age affected by NE were characterized using multiplex PCR (mPCR) and antibiotic susceptibility test. A subset of isolates (n = 75) were analyzed using pulsed-field gel electrophoresis (PFGE). Toxin typing using mPCR revealed that all C. perfringens isolates were toxinotype A. However, 68% (59 of 85) of the isolates from apparently healthy birds and 81% (119 of 145) from dead birds were positive for netB gene. Antimicrobial susceptibility testing using a disk diffusion method indicated that 53% of the isolates had a multidrug resistant profile that comprised of streptomycin, gentamicin, erythromycin, tetracycline, and bacitracin. PFGE analysis of 53 typeable isolates indicated a wide genetic relatedness even among isolate from the same state with the same antibiotic resistance profile. The results obtained from this study suggest that the presence of C. perfringens with netB gene in broiler chicken does not automatically result in death but other factors such as health of the bird before proliferation of virulent C. perfringens may be critical for development of NE.