(P27-16-26) Two Servings of Yogurt per Day Increase Lactic Acid Bacteria With No Change to Antimicrobial Resistance in the Gut Microbiome in Healthy Older Adults

Objectives: Prior studies of yogurt consumption predate shotgun sequencing and quantification of antimicrobial resistance (AMR) genes. Our objective was to determine how dairy yogurt intake impacts the gut microbiome, including AMR. We hypothesized that two servings of yogurt per day will increase lactic acid bacteria and suppress Gammaproteobacteria, a clade known to harbor AMR genes.

Methods: Healthy older adults (n=24, ages 50-75 yrs) completed the USDA Yogurt and GI Health Study in which participants completed a 2-wk baseline period without yogurt intake, a 3-wk intervention of two daily 6-oz servings of sweetened whole milk yogurt prepared with starter cultures L. acidophilus, L. bulgaricus, S. thermophilus, B. lactis, and a 2-wk follow-up period with no yogurt consumption. Stool samples were collected at baseline, after 1, 2, and 3 wks of intervention, and at follow-up. DNA was extracted from stool samples and sequenced deeply (35M reads/sample) using shotgun metagenomics. Microbiota composition was assessed using MetaPhlAn 4.2.2. AMR genes were detected by aligning merged paired end reads to the MEGARes v3.0 database. Linear mixed effects models controlling for repeated measures followed by post-hoc Tukey testing were used to assess changes in taxonomy and AMR gene abundance across stool collections.

Results: Relative abundance of all yogurt bacteria except L. acidophilus were significantly enriched during yogurt intervention compared to baseline and post-intervention periods (ANOVA, p=0.0004). Relative abundance of Gammaproteobacteria did not change. Microbial community composition during all intervention timepoints differed significantly from baseline and follow-up (PERMANOVA, Weighted UniFrac dissimilarity R²=0.017, p=0.005). Differential abundance analysis suggests this change in beta-diversity is driven by introduction of yogurt bacteria. Neither total nor AMR genes related to drug, metal, or multi-compound resistance changed across study period.

Conclusions: Yogurt associated bacteria are present and detectable in stool samples after 1 wk of yogurt intervention, and undetectable after a 2-wk washout period. Two, daily 6-oz servings of yogurt do not introduce AMR genes into the microbiome via introduction of yogurt associated bacteria or compositional shifts in the microbiota.

Funding Sources: California Dairy Research Foundation