Exploring the effect of the foodborne pathogen Bacillus cereus on the growth, immunity, and gut microbiota of mice

Bacillus cereus, a common spore-forming bacterium, is a major cause of foodborne illness worldwide. This study investigated its effects on mouse physiology and wellbeing-including body-weight trajectory, digestive/oxidative biochemistry, liver-based immune enzyme proxies, and the gut microbiota. Mice were given oral doses of B. cereus at concentrations ranging from 10³ to 10⁷ CFU/mL over seven days. Exposure resulted in acute physiological responses, including transient growth suppression, altered antioxidant enzyme activity (increased Total Antioxidant Capacity [T-AOC] and Superoxide Dismutase [SOD], decreased Lysozyme [LZM]), and reduced blood glucose and amylase levels, particularly at lower doses. These findings suggest immune disruption and metabolic imbalance. Gut microbiota analysis revealed marked compositional shifts, characterized by increased richness, a decreased Firmicutes/Bacteroidota ratio, enrichment of Akkermansia muciniphila, and a decline in beneficial genera such as Lactobacillus. Functional prediction indicated suppression of microbial pathways related to penicillin/cephalosporin biosynthesis. Collectively, these results indicate that short-term B. cereus exposure perturbs physiological status and the gut ecosystem, even at low doses, outlining potential subclinical risks of B. cereus contamination and implications for gut health and food safety.