Entry 15
Probiotic science page
Adheres to vaginal epithelial cells to displace pathogenic bacteria and reduce recurrent bacterial vaginosis, with RCT evidence.
Overview
Lactobacillus crispatus CTV-05 (strain IP174178) is the active ingredient in LACTIN-V. This is the first vaginal live biotherapeutic product (LBP) to complete phase 2b clinical trials. It aims to prevent recurrent bacterial vaginosis (BV) [1,7]. L. crispatus is the bacterial species most strongly linked to a healthy vaginal microbiome. When it disappears, that is a hallmark of BV imbalance [7]. LACTIN-V comes as a vaginal suppository. It contains freeze-dried L. crispatus CTV-05 at 2×10^8 CFU (colony-forming units, a live bacteria count) or more per dose. It is designed to repopulate the vagina with protective lactobacilli after antibiotic treatment [4,7]. Multiple randomized controlled trials have shown it reduces BV recurrence. It has also been studied for preventing HIV infection and supporting IVF outcomes [1–4]. L. crispatus stayed in the emended genus Lactobacillus (sensu stricto) after the 2020 reclassification [7].
Mechanism
LACTIN-V works by direct ecological replacement. After antibiotics clear away the BV-linked imbalance, the added L. crispatus CTV-05 settles on the vaginal lining. It produces lactic acid and bacteriocins (bacteria-killing compounds). These keep the pH low and block harmful bacteria from coming back [7]. A multi-omics analysis of the phase 2b trial showed that an L. crispatus-dominant microbiome was achieved in 30% of LBP recipients. Only 9% of placebo recipients reached this state. This means a benefit ratio of 3.31 (P<0.005) by week 12. The effect came mainly from CTV-05 colonization [1]. Inflammatory cytokines dropped in both groups after metronidazole treatment. But they bounced back to baseline in the placebo group. The LBP group kept them suppressed [1].
Colonization success depends on the state after antibiotics. LACTIN-V reduced BV recurrence at 12 weeks only in women who reached clinical cure after metronidazole. The risk ratio was 0.56 (95% CI 0.35–0.77). It did not work for those without post-antibiotic cure [4]. There are three colonization types: sustained, transient, and colonization-resistant. Each is linked to distinct genital immune profiles. Women who resist colonization have higher pre-treatment vaginal microbiota diversity and signs of epithelial disruption [5]. In a South African phase 2 trial, LACTIN-V changed the vaginal microbiota and reduced genital tract inflammation in women at high risk of HIV infection [3].
Health Benefits
Phase 2b RCT (recurrent BV): LACTIN-V reduced BV recurrence at 12 weeks compared to placebo. It worked best in women who had initial clinical cure after metronidazole [1,4]. (Evidence level: human RCT)
RCT (IVF): A randomized, double-blind, placebo-controlled multicentre trial found that clindamycin plus LACTIN-V improved vaginal imbalance in IVF patients [2]. (Evidence level: human RCT)
Phase 2 RCT (HIV risk): LACTIN-V reduced genital tract inflammation and changed the vaginal microbiota in South African women at high risk of HIV infection [3]. (Evidence level: human RCT)
Colonization and immune impact: CTV-05 colonization (at 10^6 CFU/mL or more) was reached by 72% of participants during treatment. Sustained colonization was linked to distinct immune profiles [5]. (Evidence level: human observational, nested in RCT)
Safety in pregnancy: LACTIN-V was safe, tolerable, and acceptable in pregnant women at high risk of preterm birth [6]. (Evidence level: human safety study)
Biology
Strain identity: L. crispatus CTV-05, first isolated from the vaginal microbiome of a healthy woman [7].
Colonization dynamics: Three colonization types: sustained (31%), transient (41%), and resistant (28%). These are defined by whether CTV-05 persists after stopping the product [5].
Ecological mechanism: CTV-05 competes with BV-linked bacteria for spots to stick to on the vaginal lining. Native L. crispatus strains also help rebuild the post-treatment microbiome [1].
Taxonomy: L. crispatus belongs to the L. acidophilus group within the narrowed genus Lactobacillus (sensu stricto). It was not moved to a new genus in the 2020 reclassification [7].
Bibliography
[1] Bloom SM, et al. (2026). “Vaginal microbiota impacts of a Lactobacillus crispatus live biotherapeutic and predictors of colonization in randomized controlled trial.” Cell Host Microbe. 34(4):734–750.e10. PMID: 41903526
[2] Haahr T, et al. (2025). “Efficacy of clindamycin and LACTIN-V for in vitro fertilization patients with vaginal dysbiosis: a randomised double-blind, placebo-controlled multicentre trial.” Nat Commun. 16(1):5166. PMID: 40467561
[3] Hemmerling A, et al. (2025). “Effect of the vaginal live biotherapeutic LACTIN-V (Lactobacillus crispatus CTV-05) on vaginal microbiota and genital tract inflammation among women at high risk of HIV acquisition in South Africa: a phase 2, randomised, placebo-controlled trial.” Lancet Microbe. 6(6):101037. PMID: 40194532
[4] Hemmerling A, Wierzbicki MR, Armstrong E, Cohen CR. (2024). “Response to Antibiotic Treatment of Bacterial Vaginosis Predicts the Effectiveness of LACTIN-V (Lactobacillus crispatus CTV-05) in the Prevention of Recurrent Disease.” Sex Transm Dis. 51(6):437–440. PMID: 38733973
[5] Armstrong E, et al. (2024). “Vaginal Lactobacillus crispatus persistence following application of a live biotherapeutic product: colonization phenotypes and genital immune impact.” Microbiome. 12(1):110. PMID: 38907268
[6] Bayar E, et al. (2023). “Safety, tolerability, and acceptability of Lactobacillus crispatus CTV-05 (LACTIN-V) in pregnant women at high-risk of preterm birth.” Benef Microbes. 14(1):45–56. PMID: 36815494
[7] Lagenaur LA, et al. (2021). “Connecting the Dots: Translating the Vaginal Microbiome Into a Drug.” J Infect Dis. 223(12 Suppl 2):S296–S306. PMID: 33330916
Available Products
LACTIN-V (Osel, Inc.): Vaginal suppository with freeze-dried L. crispatus CTV-05. Reviewed by the FDA as a live biotherapeutic product. Available through clinical trial programs and advancing toward market approval.
Strain IP174178 is available from culture collections for research.