In ovo inoculation of duck embryos with different strains of Bacillus cereus to analyse their synergistic post‐hatch anti‐allergic potentialities

BACKGROUND: Bacillus cereus is a Gram‐positive, facultative anaerobic bacteria with few strains reported to be used as probiotics for animals and birds in recent times if the doses are formulated properly. OBJECTIVES: To analyse the synergistic anti‐allergic potentiality of different Bacillus cereus strains on experimental in ovo and in vitro duck model, as probiotic immune stimulant. MATERIALS AND METHODS: Different strains of Bacillus cereus from 29 isolates were identified through 16S rRNA gene sequencing from the milk samples of buffalo breeds of South Asia. The probiotic properties were tested in aspects of gram staining, catalase test, coagulase, test, bile salt tolerance, pH tolerance and phenol tolerance test. MIC(50) and MIC(90) levels were profiled using nine different antibiotics, and antimicrobial activity against eight different enteric pathogens was assessed. Finally, the test strains of Bacillus cereus (Colony Forming Unit [CFU] 30X10(11)) were combined‐infused at different concentrations in embryonated duck eggs to assess the post‐hatch anti‐allergic effects against histamine‐induced allergic reaction and their immunoglobulin E (IgE) level was tested. RESULTS: Molecular identification confirmed the test strains as B. cereus HKS 1–1, B. cereus LOCK 1,002 and B. cereus BF2, which were all motile, spore‐forming, catalase‐positive and rod‐shaped. All were 0.3% bile salt, 0.4% phenol and pH tolerant. Two‐way ANOVA test P values revealed that B. cereus BF2 was statistically significant (p < .0014) in bile salt tolerance test. B. cereus HKS 1–1 was significant in phenol and pH tolerance at p < .0002 and p < .0489, respectively. Besides, the test strains showed antibiotic sensitivity and antimicrobial activity to different enteric pathogens. In vivo model referred the test strains as effective in partial allergy reduction at same CFU but at different concentrations with p < .0001 among the groups. CONCLUSION: The isolated and characterized strains of B. cereus showed partial immune‐stimulating potentiality against experimentally induced allergic reaction.