## 4 Discussion  
In the present study, we demonstrated the beneficial effects of four GMNL _Lactobacillus_ strains in BV intervention through observations of the reduced Nugent score and other clinical symptoms, including vaginal itching and secretion, but not the reduction of vaginal pH. [PERSON] et al. showed that the mean vaginal pH in women with BV (pH 5.0) was higher than in those without BV (pH 4.6) [22]. [PERSON] et al. and [PERSON] et al. also demonstrated that vaginal pH (cutoff value: 4.5) was relatively sensitive but less specific for Nugent score-based BV detection [22; 23]. [PERSON] et al. showed that BV women who received probiotic capsules for 14 days had a lower incidence of BV recurrence at 2-month follow-up period, but a significantly reduced vaginal pH was observed at 11-month follow-up period [24]. Hence, we suggest that the reduction of vaginal pH under VGA-1/VGA-2 supplements might require a considerable time to achieve. In addition to BV, these four GMNL _Lactobacillus_ strains might be used for the intervention of vaginal candidiasis, based on their capabilities for exclusion or competition in the adherence-inhibition of _C. albicans_ to HeLa cells (Figure S7). The inhibitions of _C. albicans_ adhesion on HeLa cells by all four GMNL _Lactobacillus_ strains, using the exclusion method, were significantly stronger than that using GR-1 or RC-14 (Figure S7B), whereas all four GMNL _Lactobacillus_ strains displayed the ability for inhibition of the adherence of _C. albicans_ to HeLa cells, which is a comparable phenomenon to GR-1 or RC-14 in the displacement (Figure S7C) or competition (Figure S7D) method. The recurrence rates of BV among participants, after VGA-1 or VGA-2 consumption, showed reductions (Figure 5). Among the participants with BV history, the increased recurrent interval time of BV during follow-up was observed in the VGA-1 and VGA-2 groups (Supplementary Table S7; 75% (6/8) in VGA-1 group and 90% (9/10) in VGA-2 group). [PERSON] et al. suggested that the recurrence of BV after treatment might result from the high densities of BV-associated bacteria in the rectum [25], which was observed in a study of bacterial loads in the vagina and rectum among pregnant women [26]. The intestinal tract serves as the primary reservoir for group B _Streptococcus_ among women with group B _Streptococcus_ infection, during pregnancy [27]. In our study, the inhibitory activity to common bacterial pathogens of the female gut or the genital tract, such as _G. vaginalis_, group B _Streptococcus_, _E. coli_, or _S. aureus_, was observed (Table 1), which might help in the control of intestinal bacterial pathogens and lead to the reduction of BV recurrence. Although the physiological reduction of vaginal _Lactobacillus_ was found in menopausal women, it did not increase their BV risk [28]. [PERSON] et al. found no significant changes in BV risk for the first six days of the menstrual cycle as compared to Day 14, but a significant increase for day 7-14 among African participants with a stable and high frequency of BV history was observed [29]. This meant that the menstrual cycle could be a factor to influence the risk of BV. Our trial only excluded pregnancy, and we did not include menstrual cycle status or menopause as a factor for the analysis, due to the lack of menstrual cycle records and the small sample size. In our study, colonization of GMNL _Lactobacillus_ strains was found in two participants in the VGA-1 group (Figure 6). In these cases, both participants were enrolled with a high initial Nugent score (score = 6 for S017 and score = 7 for S025). Significant increases in _L. crispatus_ and _L. gasseri_ were found in these cases, with the colonization of GMNL _Lactobacillus_ strains in vagina (Supplementary Table S8, the fold changes of _L. acidophilus_, _L. crispatus_, or _L. rhamnus_ were 992.9/367.1/207.2 for S017 or 445.7/236.4/146.5 for S025, respectively) and their BV or intermediate vaginal flora shifting to normal flora after 4-week-comsuption of VGA-1.