Isolation and Characterization of Spore Forming Probiotic Bacteria from Duck Stool

Abstract Introduction: The extensive use of antibiotic growth promoters (AGPs) in poultry and duck farming has raised concerns regarding antibiotic resistance and food safety. Probiotics, particularly spore-forming bacteria, represent a sustainable alternative due to their resilience and beneficial effects on gut health. Ducks, being part of both aquatic and terrestrial ecosystems, may harbor unique probiotic strains. This study aimed to isolate, identify, characterize, and evaluate the safety of spore-forming probiotic bacteria obtained from duck feces. Methods: Ten duck stool samples were collected from different locations in Jashore (Ambottola), Bangladesh. Spore-forming bacteria were isolated using selective culture media (Mannitol Egg Yolk Polymyxin agar) following enrichment by heat treatment. The isolates were subjected to morphological and biochemical tests (spore staining, starch hydrolysis, coagulation, and hemolytic activity). 16S rRNA gene sequencing was performed for molecular identification. The oral toxicity test was conducted in day-old chicken chicks by administrating the selected isolates orally for seven consecutive days, followed by monitoring clinical signs, growth performance, and mortality. Results: Molecular identification confirmed two isolates (strain 2B and 10A) as Bacillus spp., both isolates exhibited strong probiotic potential, including non-hemolytic activity, starch hydrolysis, and coagulase positivity, indicating safety and functional capability. The oral toxicity test demonstrated no adverse effects, behavioral changes, or mortality, confirming the non-toxic and safe nature of the isolates for poultry use. Conclusion: The isolated Bacillus spp. demonstrated excellent probiotic characteristics and were tested safe so far. These findings suggest their potential as sustainable probiotic candidates to replace AGPs, supporting healthier and more efficient poultry and duck production systems. Keywords: Antibiotic resistance, probiotics, spore-forming bacteria, Bacillus spp., duck feces, oral toxicity test, poultry