Effects of the Administration of Probiotics on Fecal Microbiota Diversity and Composition in Healthy Individuals

BACKGROUND/AIMS: Probiotics are expected to modify the composition of gut microbiota. We aimed to investigate the changes in the composition and diversity of gut microbiota by the administration of probiotics in healthy individuals. METHODS: Twelve healthy volunteers with age range of 30–42 years provided baseline fecal samples. Subsequently, they took commercially available probiotic capsules (a mixture for Bifidobacterium, Lactobacillus, and Enterococcus) for 4 weeks. Fecal samples were collected at 4 weeks of administration and 2 weeks after the stop of administration. Fecal microbiota was analyzed via 16S ribosomal RNA gene sequencing. RESULTS: The mean Shannon index was not significantly altered by the 4-week administration of probiotics (4.365 vs 4.556, P > 0.05). The proportion of Bacteroidetes, Actinobacteria, Firmicutes, and Proteobacteria was not significantly changed by the 4-week administration of probiotics. At the genus level, the proportions of Lactobacillus (2.138% vs 2.773%, P = 0.028) and Enterococcus (0.022% vs 2.758%, P = 0.004) significantly increased 4 weeks after the administration of probiotics, but reduced 2 weeks after the stop of administration (2.773% vs 3.292%, P = 0.064 and 2.758% vs 0.001%, P = 0.001). CONCLUSIONS: The diversity of fecal microbiota is not significantly affected by 4 weeks of probiotics administration. The proportion of fecal microbiota at the genus level is significantly altered by the administration of probiotics. However, this effect does not seem to last long, probably because of homeostasis or dietary influence.