UC Davis

One of the most common indications for probiotic treatment is the prevention of antibiotic-associated diarrhea (AAD). Bifidobacterium animalis subsp. lactis BB-12 is a safe and well-tolerated strain that has a long history of use as a probiotic in dietary supplements and fermented milk products. Our aim was to understand the capacity of the antibiotic amoxicillin-clavulanate (AMC) to alter the intestinal microbial composition and metabolome of mice when administered concurrently with either BB-12 or yogurt or both combined using 16S rRNA DNA sequencing, qPCR, and NMR metabolomics. To study the effects of BB-12, yogurt, and AMC, three cohorts of mice were used, and treatments were given through oral route in drinking water. AMC resulted in significant reductions (p<0.05) in male mouse body weight throughout whole study and a reduction in water intake for first five days when consumed in the drinking water over a ten-day regimen. AMC administration also resulted in significant (p<0.05) loss in bacterial cell numbers in the cecum and feces over time. The fecal microbiota changed within one day of the start of AMC administration. These changes included significant reductions in bacterial alpha-diversity and increases in proportions of Pseudomonadota (formerly called Proteobacteria), most notably Erwiniaceae and Enterobacteriaceae. Although there were differences in taxonomic enrichments between mouse study cohorts, the cecal contents of all mice given AMC contained lower concentrations of the short-chain fatty acids (SCFA) acetate, butyrate, and propionate and higher quantities of arginine, glutamine, glycine, proline, serine, and threonine. Overall, even after a recommended dose of AMC was administered, antibiotics impacted severely on 16S rRNA cell counts, BB-12 cells in yogurt, gut microbial community, and cecal metabolites specifically SCFA and amino acids.