Characterization of Clostridium perfringens isolates obtained from 2010 to 2012 from chickens with necrotic enteritis in Korea.

Clostridium perfringens produces diverse virulent toxins that cause necrotic enteritis in poultry, resulting in a great negative impact on the poultry industry. To study the characteristics of C. perfringens in chickens, we isolated 88 strains from chickens (1 strain per flock) with necrotic enteritis. The isolated bacterial strains were screened for toxin type and antimicrobial susceptibility. Necropsy of 17 chickens that died from necrotic enteritis revealed that their intestines were dilated with inflammatory exudates and characterized by mucosal necrosis. All the isolated strains were identified as toxin type A using multiplex PCR for toxin typing. We found that the rate of netB-positive strains isolated from dead chickens was significantly higher (8 of 17) than the rate among healthy chickens (2 of 50). We performed antimicrobial susceptibility test with 20 selected antimicrobial agents using the disk diffusion test and found that 30 tested strains were completely resistant to 5 antibiotics and partially resistant to 6 antibiotics whereas all the strains were susceptible to 9 antimicrobial agents. Using pulsed-field gel electrophoresis analysis, the 17 strains were divided into 13 genetic clusters showing high genetic diversity. In conclusion, C. perfringens strains isolated from Korean poultry showed a high resistance to antimicrobial drugs and high genetic diversity, suggesting that continuous monitoring is essential to prevent outbreaks of necrotic enteritis in chickens.