Orally ingested Lactobacillus crispatus VPC177 enhances total vaginal Lactobacillus counts—a cross-over exploratory study

Introduction The vaginal microbiome plays a crucial role in vaginal health, and disturbances in the microbial balance can negatively affect female wellbeing. In recent years, there has been growing interest in the use of probiotics and prebiotics to support a healthy vaginal microbiota. However, effects are often strain-specific and should be clinically demonstrated to influence the vaginal microbiota. This study aimed at evaluating the ability of four different orally administered probiotic strains to affect the fecal, and more specifically, the vaginal microbiota in healthy women. Methods In this open-label, cross-over, exploratory study 35 women age 20–63 years consumed four different strains, Lactobacillus crispatus VPC111, Lactobacillus gasseri VPG44, L. crispatus VPC177 and Lactiplantibacillus plantarum HEAL9 ® for 14 days each with a washout period of 14 days between each intervention period. Levels of lactobacilli were assessed in fecal and vaginal samples following each intervention period. Results VPC111, VPC177, and HEAL9 all resulted in significant increases in fecal lactobacilli after 14 days intervention compared to baseline ( p p = 0.001), whereas VPC111, VPG44, and HEAL9 showed no significant vaginal effects. Post hoc characterization of L. crispatus VPC177 demonstrated that it produces both D- and L-lactate at high levels (9.31 and 4.58 g/L, respectively) and possesses genes associated with bacteriocin production, glycogen utilization, and mucosal adhesion, supporting its potential for antimicrobial activity, carbohydrate metabolism, and colonization of the vaginal environment. Discussion These findings demonstrate that probiotic effects on the vaginal microbiota are strain-specific, and that an increase in fecal lactobacilli does not necessarily translate into corresponding changes in the vaginal microbial community. Among the strains evaluated, VPC177 was the most promising candidate for supporting vaginal health through oral probiotic administration.