A Healthy Vaginal Microbiota Remains Stable during Oral Probiotic Supplementation: A Randomised Controlled Trial

Abstract

The primary objective of this randomised, placebo-controlled, triple-blind study was to assess whether orally consumed Lactobacillus acidophilus La-14 (La-14) and Lacticaseibacillus rhamnosus HN001 (HN001) colonise a healthy human vagina. Furthermore, potential effects on vaginal microbiota and immune markers were explored. Fifty women devoid of vaginal complaints (Nugent score 0-3 and vaginal pH ≤ 4.5) were randomised into a 2-week intervention with either La-14 and HN001 as the verum product or a comparable placebo. Vaginal swab samples were collected at baseline, after one and two weeks of intervention, and after a one-week follow-up, for assessing colonisation of the supplemented lactobacilli, vaginal microbiota, and six specific immune markers. Colonisation of L. acidophilus and L. rhamnosus was not observed above the assay detection limit (5.29 and 5.11 log 10 genomes/swab for L. acidophilus and L. rhamnosus, respectively). Vaginal microbiotas remained stable and predominated by lactobacilli throughout the intervention, and vaginal pH remained optimal (at least 90% of participants in both groups had pH 4.0 or 4.5 throughout the study). Immune markers elafin and human β-defensin 3 (HBD-3) were significantly decreased in the verum group (p = 0.022 and p = 0.028, respectively) but did not correlate with any microbiota changes. Adverse events raised no safety concerns, and no undesired changes in the vaginal microbiota or immune markers were detected.

Keywords: Lacticaseibacillus rhamnosus; Lactobacillus acidophilus; immune markers; lactobacilli; microbiota; probiotics; vaginal colonisation.

Figure 1

Schedule of events in the study. The screening visit (Visit 1) was held 3 to 42 days before randomisation (Visit 2) to allow for the study endpoints to be measured in between menses. Vaginal pH was measured, and vaginal swabs samples were collected for analysis of vaginal colonisation by the supplemented Lactobacillus acidophilus La-14 and Lacticaseibacillus rhamnosus HN001 and for assessment of the vaginal microbiota and immune markers at baseline (Visit 2) before investigational product (IP) consumption at weekly intervals during the intervention (Visit 3 and 4) and after a 1-week follow-up (Visit 5). Throughout the study, participants collected information on adverse events, concomitant medications, IP compliance, sexual behaviour, contraceptive method used, and menstrual bleeding days on a diary. A gynecological examination and vital signs’ measurement were performed on each visit as the physical examination. AE, adverse event; BMI, body mass index; CM, concomitant medication; HN001, Lacticaseibacillus rhamnsosus HN001; ICF, informed consent form; La-14, Lactobacillus acidophilus La-14; MH, medical history.

Figure 2

CONSORT flow diagram of the 21-day intervention study of triple-blind, randomised, and placebo-controlled design. Placebo: maltodextrin; Verum: 10¹⁰ CFU Lactobacillus acidophilus La-14 and Lacticaseibacillus rhamnosus HN001. CONSORT, consolidated standards of reporting trials; ITT, intention-to-treat.

Figure 3

Relative abundance of species in the vaginal microbiota for verum and placebo participants consuming 10¹⁰ CFU Lactobacillus acidophilus La-14 and Lacticaseibacillus rhamnosus HN001, or maltodextrin daily for two weeks between Visits 2 and 4. Visit 2, baseline visit; Visit 3, after one week of intervention; Visit 4, after two weeks of intervention; Visit 5, after a one-week follow-up.

Figure 4

β−diversity (weighted UniFrac metric) depicting sample clustering of the vaginal microbiota samples from study participants by intervention group and visit in a principal coordinate analysis (PCoA) plot. Ellipses represent 95% confidence interval. Visit 2, baseline visit; Visit 3, after one week of intervention; Visit 4, after two weeks of intervention; Visit 5, after a one-week follow-up.