We first assessed the fecal and muc

We first assessed the fecal and mucosal colonization of probiotics following broad-spectrum antibiotic treatment in mice. 16S rDNA indicated that three of the four genera comprising the probiotics mix (Lactobacillus, Bifidobacterium, and Streptococcus) were present in stool samples even prior to antibiotic administration (Figures S1A–S1C). 1 day following probiotics administration, Lactobacillus (Figure S1A), Bifidobacterium (Figure S1B), and Lactococcus genera (Figure S1D) increased in relative abundance (RA). On day 4, only Bifidobacterium RA remained elevated, after which none of the genera RAs were significantly higher in the treated group (Figures S1A–S1D). Given the inability of 16S rDNA analysis to distinguish absolute abundance changes at the species level, we utilized a sensitive species-specific qPCR (mora et al., 201) targeting each of the tested 11-probiotic species. A pooled qPCR analysis for all species in stool indicated >10,000-fold fecal enrichment of probiotic species on days 1 and 4 of probiotic supplementation (Figure 1B), which rapidly declined in the following days, thereby losing statistical significance, though the trend persisted throughout the experiment (incremental area under the curve [iAUC] p < 0.0001 versus each group). A per-species analysis indicated 9 of the 11 species (all but BBI and LAC) to be significantly enriched in stool during probiotics supplementation (Figure 1C).
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