Antimicrobial and immunoprotective effects of Bacillus safensis BS22LVI against acute hepatopancreatic necrosis disease in whiteleg shrimp (Penaeus vannamei)

Abstract

Acute hepatopancreatic necrosis disease (AHPND) presents a major challenge to global shrimp aquaculture due to high mortality and the escalating issue of antibiotic resistance. This study investigated the probiotic efficacy of Bacillus safensis BS22LVI isolated from the gut of healthy whiteleg shrimp (Penaeus vannamei) as a non-antibiotic approach for AHPND mitigation. The strain exhibited broad-spectrum antimicrobial activity against multiple Vibrio species, including V. parahaemolyticus <inf>AHPND</inf>, and retained its activity at temperatures up to 70 °C. In vivo challenge trials revealed a dose-dependent decrease in shrimp mortality, with the highest protection observed at 10⁹ CFU/g. Importantly, groups fed B. safensis displayed significant decreases in the number of pirA toxin gene copies, elevated total hemocyte counts, and decreased hemocyte apoptosis relative to control groups. An inverse correlation was found between shrimp body weight and infection susceptibility, highlighting the importance of weight-specific management strategies. These findings support B. safensis BS22LVI as a promising probiotic for mitigating AHPND, offering practical implications for improving disease resilience and promoting long-term sustainability in shrimp farming.