Microbiome and Antiaging Medicine: Vaginal Microbiome and Antiaging

The ideal vaginal environment is a state where the vaginal microbiome, i.e., the bacterial flora in the vagina, is predominantly composed of lactic acid bacteria, mainly of the Lactobacillus genus. The vagina maintains its self-cleaning function under the presence of lactic acid bacteria, and a correlation with health benefits such as reduced risk of gynecological diseases has been shown. The Lactobacillus genus is classified as the largest genus among lactic acid bacteria and is widely distributed in nature, and is also included in fermented foods. Lactobacilli are primarily classified into five communities (community-state type; CST) in molecular studies based on the cluster state of the bacterial species [1]. CST I is Lactobacillus crispatus, CST II is Lactobacillus gasseri, CST III is Lactobacillus iners, CST V is Lactobacillus jensenii, and the diverse group with fewer lactobacilli is classified as CST IV (subtypes A, B). CST I is the most common species in the Lactobacillus genus, with a pH of 4.4 or less. CST IV lacks lactic acid bacteria and is dominated by diverse anaerobic bacteria, with a pH of 5.3 or higher [1]. CST IV is a state with many bacterial vaginosis-related organisms in the vaginal microbiome, and it has been shown to increase the risk of sexually transmitted diseases and human papillomavirus (HPV) infection, decrease fertility, promote inflammation, affect immune regulation, and increase the risk of gynecological cancer [2–5]. Also, the proportion of each CST varies by race. In a cohort study targeting sexually mature women, the overall prevalence of lactic acid bacteria-dominated CST I, II, III, and V was 73% on average for all races, 80% for Asians, and when viewed by CST, the most common CST for Asians was CST III at 41%. The prevalence of the diverse group CST IV was 27% on average for all races and 19% for Asians [1].