Multi-Strain Probiotic Supplementation with a Product Containing Human-Native S. salivarius K12 in Healthy Adults Increases Oral S. salivarius

Streptococcus salivarius (S. salivarius) K12 supplementation has been found to reduce the risk of recurrent upper respiratory tract infections. Yet, studies have not reported the effect of supplementation on oral S. salivarius K12 levels or the salivary microbiome. This clinical trial was designed to determine how supplementation with S. salivarius K12 influences the oral microbiome. In a randomized, double-blind, placebo-controlled trial, 13 healthy adults received a probiotic powder (PRO) containing Lactobacillus acidophilus, Bifidobacterium lactis, and S. salivarius K12 and 12 healthy adults received a placebo-control powder (CON) (n = 12) for 14 consecutive days. Oral S. salivarius K12 and total bacteria were quantified by qPCR and the overall oral microbiome was measured using 16S rRNA amplicon sequencing. Supplementation significantly increased mean salivary S. salivarius K12 levels by 5 logs compared to baseline for the PRO group (p < 0.0005), which returned to baseline 2 weeks post-supplementation. Compared with the CON group, salivary S. salivarius K12 was 5 logs higher in the PRO group at the end of the supplementation period (p < 0.001). Neither time nor supplementation influenced the overall oral microbiome. Supplementation with a probiotic cocktail containing S. salivarius K12 for two weeks significantly increased levels of salivary S. salivarius K12.