A novel Bacillus subtilis strain alleviates necrotic enteritis in chickens by reducing NetB toxin from Clostridium perfringens.
Source: PubMed, NCBI / U.S. National Library of Medicine
Probiotic strategies that attenuate virulence-associated toxins are increasingly recognized as effective approaches to mitigate disease progression. We screened for wildtype Bacillus strains from healthy chickens with the aim of identifying specific isolates capable of reducing Clostridium perfringens toxin production and necrotic enteritis (NE) lesions in chickens and consequently selected a strain (Bacillus subtilis CG4). The cell-free culture supernatant (CFS) of CG4 did not inhibit the growth of a C. perfringens Type G strain. However, the bacterium significantly reduced the level of NetB toxin (a key toxin for NE development) produced by C. perfringens. B. subtilis CG4 was therefore further characterized in vitro and evaluated in vivo for its ability to reduce NE. In the in vitro studies, CG4 produced nearly 3.0 × 10⁸ spores/mL and exhibited resistance to tetracycline and the penicillin only among tested antibiotics. In addition, the CG4 CFS was sensitive to heat and proteinase K treatments, suggesting the proteinaceous nature of a bioactive component. The proteolytic activity of CG4 CFS possessed a relatively broad substrate spectrum, which effectively digested bovine serum albumin (BSA) and casein. In a C. perfringens infection chicken trial that contained three groups of birds (no treatment, pathogen infection only, and pathogen infection with the treatment of CG4) and used a completely random design, the supplementation of B. subtilis CG4 in feed resulted
Abstract
Probiotic strategies that attenuate virulence-associated toxins are increasingly recognized as effective approaches to mitigate disease progression. We screened for wildtype Bacillus strains from healthy chickens with the aim of identifying specific isolates capable of reducing Clostridium perfringens toxin production and necrotic enteritis (NE) lesions in chickens and consequently selected a strain (Bacillus subtilis CG4). The cell-free culture supernatant (CFS) of CG4 did not inhibit the growth of a C. perfringens Type G strain. However, the bacterium significantly reduced the level of NetB toxin (a key toxin for NE development) produced by C. perfringens. B. subtilis CG4 was therefore further characterized in vitro and evaluated in vivo for its ability to reduce NE. In the in vitro studies, CG4 produced nearly 3.0 × 10⁸ spores/mL and exhibited resistance to tetracycline and the penicillin only among tested antibiotics. In addition, the CG4 CFS was sensitive to heat and proteinase K treatments, suggesting the proteinaceous nature of a bioactive component. The proteolytic activity of CG4 CFS possessed a relatively broad substrate spectrum, which effectively digested bovine serum albumin (BSA) and casein. In a C. perfringens infection chicken trial that contained three groups of birds (no treatment, pathogen infection only, and pathogen infection with the treatment of CG4) and used a completely random design, the supplementation of B. subtilis CG4 in feed resulted in a significant reduction in NE lesions (p ≤ 0.05) compared to the birds infected with the pathogen only. The average NE sore of birds from the CG4-treated and C. perfringens-infected only groups were 2.47 and 3.75, respectively, while the untreated group had 0 NE lesions. Additionally, CG4-treated chickens exhibited a noticeable increase in body weight (p ≤ 0.05) at the end of trial, presumably through proteolytic activity in CG4.