The antimicrobial peptide sublancin ameliorates necrotic enteritis induced by Clostridium perfringens in broilers

Sublancin is an antimicrobial peptide produced by Bacillus subtilis 168 containing 37 amino acids. The objective of this study was to investigate its inhibitory efficacy against Clostridium perfringens both in vitro and in vivo. In the in vitro study, we determined that sublancin had a minimum inhibitory concentration of 8 mu M against C. perfringens, which was much higher than the antibiotic lincomycin (0.281 mu M). Scanning electron microscopy showed that sublancin damaged the morphology of C. perfringens. The in vivo study was conducted on broilers for a 28-d period using a completely randomized design. A total of 252 chickens at 1 d of age were randomly assigned to 1 of 6 treatments including an uninfected control; an infected control; 3 infected groups supplemented with sublancin at 2.88, 5.76, or 11.52 mg activity/L of water; and an infected group supplemented with lincomycin at 75 mg activity/L of water (positive control). Necrotic enteritis was induced in the broilers by oral inoculation of C. perfringens on d 15 through 21. Thereafter, the sublancin or lincomycin were administered fresh daily for a period of 7 days. The C. perfringens challenge resulted in a significant decrease in ADG (P < 0.05) and a remarkable deterioration in G:F (P < 0.05) during d 15 to 21 of the experiment. There was a sharp increase of C. perfringens numbers in the cecum (P < 0.05). The addition of sublancin or lincomycin reduced caecal C. perfringens counts (P < 0.05). The Lactobacilli counts had a tendency to decrease in the lincomycin treatment (P = 0.051) but were the highest in the sublancin treatment (5.76 mg activity/L of water). A higher villus height to crypt depth ratio in the duodenum and jejunum as well as a higher villus height in the duodenum were observed in broilers treated with sublancin or lincomycin (P < 0.05) compared with infected control broilers. It was observed that sublancin and lincomycin decreased IL-1 beta, IL-6, and tumor necrosis factor-alpha levels (P < 0.05) in the ileum compared with the infected control. In conclusion, although sublancin's minimum inhibitory concentration is much higher than lincomycin in vitro, less sublancin is needed to control necrotic enteritis induced by C. perfringens in vivo than lincomycin. These novel findings indicate that sublancin could be used as a potential antimicrobial agent to control necrotic enteritis.