Association Between Continuous Consumption of Yogurt Fermented with Lactobacillus delbrueckii ssp. bulgaricus OLL1073R-1, Salivary Antimicrobial Proteins, and Tongue-Coating Microbiota: An Observational Human Study

<b>Background/Objectives</b>: Oral microbial homeostasis is crucial for overall health. Nonetheless, the relationship between probiotics and the oral environment remains unclear. This study investigated the association between continuous consumption of yogurt containing <i>Lactobacillus delbrueckii</i> ssp. <i>bulgaricus</i> OLL1073R-1 (LbR1 yogurt), salivary antimicrobial proteins (AMPs), tongue-coating microbiota, and upper respiratory tract infection (URTI) frequency. <b>Methods</b>: This observational study was conducted on 53 nursing home care workers, categorized into a group who consumed LbR1 yogurt daily for over 1 year (<i>n</i> = 40, yogurt group) and a non-intake group (<i>n</i> = 13, non-yogurt group). Salivary and tongue-coating samples were collected. <b>Results</b>: The yearly URTI frequency was lower in the yogurt group than in the non-yogurt group (<i>p</i> = 0.003). The salivary β-defensin-2 (HBD2) and β-defensin-3 (HBD3) flow rates were higher in the yogurt group than in the non-yogurt group (<i>p</i> = 0.02 and <i>p</i> = 0.0009, respectively). <i>Fusobacterium nucleatum</i> (<i>F. nucleatum</i>) ssp. <i>animalis</i> abundance was lower in the yogurt group than in the non-yogurt group (<i>p</i> = 0.04). Bayesian network analysis indicated an association between yogurt consumption and the yearly URTI frequency and salivary HBD2 and HBD3 flow rates. <b>Conclusions</b>: Continuous consumption of LbR1 yogurt was associated with elevated salivary HBD2 and HBD3, reduced abundance of <i>F. nucleatum</i> ssp. <i>animalis</i>, and decreased URTI frequency. Thus, LbR1 yogurt intake is associated with modulated oral immunity and microbiota, suggesting a potential link to reduced URTIs. However, as an observational pilot study, its results should be interpreted with caution.