Probiotic colonization dynamics after oral consumption of VSL#3® by antibiotic-treated mice.

Background: The ability of probiotic strains to provide health benefits to the host partially hinges on the survival of gastrointestinal passage and temporary colonization of the digestive tract. This study aims to investigate the colonization profile of individual probiotic strains comprising the commercial product VSL#3^® and determine their impact on the host intestinal microbiota. Methods: Using a cefoperazone-treated mouse model of antibiotic treatment, we investigated the impact of oral gavage with ~10⁸ CFU commercial VSL#3^® product on the intestinal microbiota using 16S-based amplicon sequencing over 7 days. Results: Results showed that probiotic strains in the formulation were detected in treated murine fecal samples, with early colonization by Streptococcus thermophilus and Lactiplantibacillus plantarum subsp. plantarum, and late colonization by Lacticaseibacillus paracasei subsp. paracasei, Bifidobacterium breve and Bifidobacterium animalis subsp. lactis. Overall, VSL#3^® consumption is associated with increased alpha diversity in the cecal microbial community, which is important in the context of antibiotic consumption. Probiotic supplementation resulted in an expansion of Proteobacteria, Bacteroidetes, and Actinobacteria, especially Bifidobacteriaceae and Lachnospiraceae, which are associated with Clostridioides difficile resistance in the murine gut. Conclusion: This study illustrates the need for determining the ability of probiotics to colonize the host and impact the gut microbiota, and suggests that multiple doses may be warranted for extended transient colonization. In addition, follow-up studies should determine whether VSL#3^® can provide resistance against C. difficile colonization and disease in a mouse model.