L. crispatus

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Health Goals: immunity digestion inflammation

Research Overview

Across the cited literature, Lactobacillus crispatus has been most studied as a defining member of “healthy” vaginal microbiome community types and as a comparator to other common Lactobacillus species (notably L. iners) in relation to bacterial vaginosis (BV), vaginal pH, and Nugent scoring. Large cross-sectional sequencing studies have characterized vaginal community state types in asymptomatic women, showing that many healthy communities are Lactobacillus-dominated (including L. crispatus-dominant states) and that community composition varies across individuals and ethnic groups alongside differences in vaginal pH. Systematic reviews of molecular studies further consolidate these patterns, emphasizing BV as a polybacterial dysbiosis and positioning L. crispatus-dominant communities as a particularly stable, health-associated configuration compared with L. iners-dominant states. More recent longitudinal/within-person work has also examined temporal dynamics, including menstrual-cycle-associated shifts in vaginal diversity with subsequent expansion of Lactobacillus spp., and has identified clear clustering of vaginal communities with L. crispatus as one dominant state.

The strongest evidence supports an association between L. crispatus dominance and a vaginal microenvironment consistent with health—typically lower pH, lower Nugent scores, and reduced likelihood of BV compared with dysbiotic states—and suggests that L. crispatus is more protective than L. iners, which is frequently observed both in health and in BV and is often interpreted as a transitional or less protective state. Interventional evidence also supports a causal role for restoring L. crispatus in reducing BV recurrence: a randomized, double-blind, placebo-controlled phase 2b trial of a live biotherapeutic containing L. crispatus (Lactin-V) administered after metronidazole showed significantly lower BV recurrence at 12 weeks (and a sustained benefit through 24 weeks) versus placebo. Collectively, these findings align cross-sectional ecological associations with clinical trial data indicating that re-establishing L. crispatus can improve BV-related outcomes.

Key gaps remain. Determinants of L. crispatus colonization and persistence (including behavioral, demographic, and host factors) are still reported as scarce and inconsistent, and cross-population differences underscore the need for refined “normal” reference ranges that account for inter-individual and ethnic variability. Mechanistic understanding is also incomplete: while lactic-acid-associated ecology is implicated, the specific strain-level functions, host–microbe immune interactions, and causal pathways linking L. crispatus to protection from BV and downstream outcomes (e.g., STI susceptibility, adverse pregnancy outcomes) require deeper characterization using longitudinal multi-omics and immunologic profiling. Finally, more phase 3 trials and comparative effectiveness studies are needed to define optimal dosing, durability, and generalizability of L. crispatus-based interventions across diverse populations and across menstrual-cycle contexts where transient increases in diversity/dysbiosis are common.

1. What conditions has L. crispatus been studied for?

  • Bacterial vaginosis (BV): Multiple abstracts focus on BV as a Lactobacillus-deficient/dysbiotic state and discuss L. crispatus as a “more beneficial” Lactobacillus species compared with L. iners, including recurrence after antibiotics and strategies to restore L. crispatus dominance.

  • Recurrent BV after antibiotic treatment: A phase 2b randomized trial evaluated a vaginal probiotic containing L. crispatus (Lactin-V) after vaginal metronidazole to prevent recurrence.

  • Vaginal dysbiosis / non-optimal vaginal microbiome states: Several abstracts describe community “cluster” types (including L. crispatus-dominant vs anaerobe-rich communities) and their relationship to vaginal pH and Nugent score (a BV-associated diagnostic score).

  • Sexually transmitted infections (risk associations): One abstract states that women with low vaginal levels of L. crispatus are at increased risk of sexually transmitted infections (STIs). A systematic review abstract also notes dysbiosis is associated with HIV, HPV, and Trichomonas vaginalis infection, and positions lactobacilli-dominant states as healthier.

  • Adverse reproductive outcomes (risk associations): One abstract states low L. crispatus is associated with increased risk of preterm birth and fertility treatment failure.

  • Gynecologic cancers (risk associations): One abstract states low L. crispatus is associated with increased risk of gynecological cancers.

  • High-risk HPV (HR-HPV) infection (intervention explored): A pilot study abstract mentions intravaginal transplantation of a vaginal-isolated natural probiotic strain for HR-HPV; the provided excerpt is incomplete, so the specific strain and outcomes cannot be confirmed from the text shown.

  • Menstrual cycle–related vaginal microbiome changes: A cohort study examined how cycle phase relates to vaginal microbiome composition, including clusters dominated by L. crispatus.

2. Does it work in treating those conditions? Summarize the evidence.

  • BV recurrence prevention (best direct evidence in the abstracts): In a randomized, double-blind, placebo-controlled phase 2b trial of Lactin-V (L. crispatus) used after vaginal metronidazole, BV recurrence by week 12 occurred in 30% of the Lactin-V group vs 45% of placebo (risk ratio 0.66, 95% CI 0.44–0.87; P = 0.01). By week 24, the risk ratio was 0.73 (95% CI 0.54–0.92). This supports efficacy for reducing recurrence after standard antibiotic therapy.

  • BV treatment/restoration of “optimal” microbiome (supportive but indirect): A systematic review abstract concludes lactobacilli-dominated vaginal microbiota are associated with a healthy micro-environment and that L. crispatus is more beneficial than L. iners. It also notes longitudinally that L. crispatus-dominant states tend to shift to L. iners-dominant or mixed lactobacilli more often than to full dysbiosis—suggesting relative stability/health association, but this is not the same as proving treatment efficacy.

  • Metabolite-based approach to promote L. crispatus dominance (preclinical): One abstract reports that oleic acid and similar long-chain fatty acids inhibit L. iners while enhancing L. crispatus growth, and that oleic acid promoted L. crispatus dominance more effectively than antibiotics in an in vitro BV model. This is promising mechanistic/preclinical evidence, not clinical proof.

  • STIs, preterm birth, fertility outcomes, cancers (association, not treatment): The abstracts state that low L. crispatus levels are linked to higher risk of several outcomes (STIs, preterm birth, fertility treatment failure, gynecologic cancers), but they do not provide interventional evidence that supplementing L. crispatus treats or prevents these outcomes.

  • HR-HPV intervention (insufficient details in provided text): The HR-HPV pilot study excerpt is incomplete; from the provided abstract fragment, efficacy cannot be assessed.

3. What health benefits does it have?

  • Association with a healthy vaginal micro-environment: Across the abstracts, lactobacilli-dominated communities are repeatedly described as “healthy,” and L. crispatus-dominant communities are one of the major healthy community types identified by 16S profiling in asymptomatic women.

  • Lower BV risk / healthier Nugent score and pH patterns (associative): The community patterns described are linked to Nugent scores (used in BV diagnosis) and vaginal pH. Lactobacilli (including L. crispatus) are tied to the conserved ecological function of lactic acid production, which is consistent with maintaining lower pH—an environment generally considered protective in these abstracts.

  • More beneficial than L. iners: The systematic review explicitly states L. crispatus is more beneficial than L. iners. Another abstract characterizes L. iners as a “transitional” species that can be present in BV and may offer less protection, indirectly highlighting L. crispatus as the more protective comparator.

  • Reduced BV recurrence after antibiotics (clinical benefit): The Lactin-V trial demonstrates a clinically meaningful reduction in BV recurrence when L. crispatus is used after metronidazole.

  • Potential resilience/fitness advantages in the vaginal environment (mechanistic): The oleic-acid abstract suggests L. crispatus can exploit certain fatty-acid–related pathways (e.g., oleate hydratase activity and efflux mechanisms) that may help it persist and outcompete less beneficial species in dysbiotic contexts (shown in vitro).

  • Possible linkage with hormonal milieu: In the menstrual-cycle study, expansion of Lactobacillus spp. after menses correlated with serum oestradiol, and the authors note this supports a possible hormonal mechanism for maintaining L. crispatus (correlation reported as r = 0.11, P < 0.001). This is supportive context rather than a direct “benefit,” but it helps explain when/why L. crispatus dominance may be more likely.

4. Does it have any downsides or side effects?

  • Adverse effects not described in the provided abstracts: The Lactin-V trial excerpt provided reports efficacy outcomes but does not include safety/adverse event details in the text shown, so specific side effects cannot be summarized from these abstracts alone.

  • Not all lactobacilli-dominant states are “universally” protective for all conditions: The systematic review abstract notes that Candida colonization is more common in women with a lactobacilli-dominated vaginal microbiome than in women with dysbiosis. This does not prove L. crispatus causes yeast infections, but it is a potential trade-off/association to be aware of when interpreting “lactobacilli dominance” as uniformly beneficial.

  • Natural fluctuation and potential misclassification during menses: The menstrual-cycle study found higher vaginal microbiome diversity and more women meeting a “dysbiotic” threshold during menses (58% with <60% Lactobacillus spp., dropping to 32% follicular and 29% luteal). This suggests that low Lactobacillus (including low L. crispatus) can be transient and cycle-related; a “downside” in practice is that timing can confound interpretation of tests and symptoms.

  • General limitation: Many benefits described are associative (microbiome state linked to outcomes) rather than proven causal effects of taking L. crispatus as a supplement, except for BV recurrence reduction in the Lactin-V trial.

5. Is it beneficial or harmful for any genetic variations (pharmacogenomics)?

No pharmacogenomic or human genetic-variant–specific effects are described in the provided abstracts.

  • What is described instead: One abstract reports statistically significant differences in vaginal community types and pH across ethnic groups, but this is not the same as identifying genetic variants that change response to L. crispatus or L. crispatus-based products.

  • Microbial genetics (not human pharmacogenomics): The oleic-acid abstract describes bacterial genes (e.g., ohyA, farE) that help L. crispatus tolerate and utilize oleic acid, which could influence how L. crispatus responds to certain metabolites. This is relevant to strain biology and formulation strategy, but it does not establish human genotype-dependent benefits or harms.

References

  1. Vaginal microbiome of reproductive-age women.
    Jacques Ravel, Pawel Gajer, Zaid Abdo, G Maria Schneider, Sara S K Koenig, Stacey L McCulle, Shara Karlebach, Reshma Gorle, Jennifer Russell, Carol O Tacket, Rebecca M Brotman, Catherine C Davis, Kevin Ault, Ligia Peralta, Larry J Forney (2011) - Proceedings of the National Academy of Sciences of the United States of America
  2. Randomized Trial of Lactin-V to Prevent Recurrence of Bacterial Vaginosis.
    Craig R Cohen, Michael R Wierzbicki, Audrey L French, Sheldon Morris, Sara Newmann, Hilary Reno, Lauri Green, Steve Miller, Jonathan Powell, Thomas Parks, Anke Hemmerling (2020) - The New England journal of medicine
  3. Contribution ofLactobacillus inersto Vaginal Health and Diseases: A Systematic Review
    Nengneng Zheng, Renyong Guo, Jinxi Wang, Wei Zhou, Zongxin Ling (2021)
  4. The vaginal microbiota: what have we learned after a decade of molecular characterization?
    Janneke H H M van de Wijgert, Hanneke Borgdorff, Rita Verhelst, Tania Crucitti, Suzanna Francis, Hans Verstraelen, Vicky Jespers (2014) - PloS one
  5. Bacterial vaginosis: a review of approaches to treatment and prevention.
    Carmen Abbe, Caroline M Mitchell (2023) - Frontiers in reproductive health
  6. The healthy female microbiome across body sites: effect of hormonal contraceptives and the menstrual cycle.
    Maria Christine Krog, Luisa W Hugerth, Emma Fransson, Zahra Bashir, Anders Nyboe Andersen, Gabriella Edfeldt, Lars Engstrand, Ina Schuppe-Koistinen, Henriette Svarre Nielsen (2022) - Human reproduction (Oxford, England)
  7. Vaginal Lactobacillus fatty acid response mechanisms reveal a metabolite-targeted strategy for bacterial vaginosis treatment.
    Meilin Zhu, Matthew W Frank, Christopher D Radka, Sarah Jeanfavre, Jiawu Xu, Megan W Tse, Julian Avila Pacheco, Jae Sun Kim, Kerry Pierce, Amy Deik, Fatima Aysha Hussain, Joseph Elsherbini, Salina Hussain, Nondumiso Xulu, Nasreen Khan, Vanessa Pillay, Caroline M Mitchell, Krista L Dong, Thumbi Ndung'u, Clary B Clish, Charles O Rock, Paul C Blainey, Seth M Bloom, Douglas S Kwon (2024) - Cell
  8. Effectiveness of vaginal probiotics
    Yujuan Liu, Xiumiao Zhao, Fei Wu, Jie Chen, Juanzhen Luo, Chunling Wu, Tingtao Chen (2024) - Aging
  9. Impact of
    R Mändar, G Sõerunurk, J Štšepetova, I Smidt, T Rööp, S Kõljalg, M Saare, K Ausmees, D D Le, M Jaagura, S Piiskop, H Tamm, A Salumets (2023) - Beneficial microbes
  10. Vaginal microbiome-host interactions modeled in a human vagina-on-a-chip.
    Gautam Mahajan, Erin Doherty, Tania To, Arlene Sutherland, Jennifer Grant, Abidemi Junaid, Aakanksha Gulati, Nina LoGrande, Zohreh Izadifar, Sanjay Sharma Timilsina, Viktor Horváth, Roberto Plebani, Michael France, Indriati Hood-Pishchany, Seth Rakoff-Nahoum, Douglas S Kwon, Girija Goyal, Rachelle Prantil-Baun, Jacques Ravel, Donald E Ingber (2022) - Microbiome
  11. Antimicrobial properties of Lactobacillus cell-free supernatants against multidrug-resistant urogenital pathogens.
    Marina Scillato, Ambra Spitale, Gino Mongelli, Grete Francesca Privitera, Katia Mangano, Antonio Cianci, Stefania Stefani, Maria Santagati (2021) - MicrobiologyOpen
  12. Cysteine dependence of Lactobacillus iners is a potential therapeutic target for vaginal microbiota modulation.
    Seth M Bloom, Nomfuneko A Mafunda, Benjamin M Woolston, Matthew R Hayward, Josephine F Frempong, Aaron B Abai, Jiawu Xu, Alissa J Mitchell, Xavier Westergaard, Fatima A Hussain, Nondumiso Xulu, Mary Dong, Krista L Dong, Thandeka Gumbi, F Xolisile Ceasar, Justin K Rice, Namit Choksi, Nasreen Ismail, Thumbi Ndung'u, Musie S Ghebremichael, David A Relman, Emily P Balskus, Caroline M Mitchell, Douglas S Kwon (2022) - Nature microbiology
  13. Lactobacillus iners and genital health: molecular clues to an enigmatic vaginal species.
    Johanna B Holm, Kayla A Carter, Jacques Ravel, Rebecca M Brotman (2023) - Current infectious disease reports
  14. Lactobacillus crispatus S-layer proteins modulate innate immune response and inflammation in the lower female reproductive tract.
    Alexiane Decout, Ioannis Krasias, Lauren Roberts, Belen Gimeno Molina, Chloé Charenton, Daniel Brown Romero, Qiong Y Tee, Julian R Marchesi, Sherrianne Ng, Lynne Sykes, Phillip R Bennett, David A MacIntyre (2024) - Nature communications
  15. Characteristics of Vaginal Microbiota of Women of Reproductive Age with Infections.
    Wanting Dong, Siyi Wang, Xi Wang, Guojin Xu, Qiuying Liu, Zheng Li, Na Lv, Yuanlong Pan, Qian Xiong, Donglai Liu, Baoli Zhu (2024) - Microorganisms
  16. Sustained effect of LACTIN-V (Lactobacillus crispatus CTV-05) on genital immunology following standard bacterial vaginosis treatment: results from a randomised, placebo-controlled trial.
    Eric Armstrong, Anke Hemmerling, Steve Miller, Kerianne E Burke, Sara J Newmann, Sheldon R Morris, Hilary Reno, Sanja Huibner, Maria Kulikova, Nico Nagelkerke, Bryan Coburn, Craig R Cohen, Rupert Kaul (2022) - The Lancet. Microbe
  17. Vaginal epithelial dysfunction is mediated by the microbiome, metabolome, and mTOR signaling.
    Alicia R Berard, Douglas K Brubaker, Kenzie Birse, Alana Lamont, Romel D Mackelprang, Laura Noël-Romas, Michelle Perner, Xuanlin Hou, Elizabeth Irungu, Nelly Mugo, Samantha Knodel, Timothy R Muwonge, Elly Katabira, Sean M Hughes, Claire Levy, Fernanda L Calienes, Douglas A Lauffenburger, Jared M Baeten, Connie Celum, Florian Hladik, Jairam Lingappa, Adam D Burgener (2023) - Cell reports
  18. Urobiome and Inflammation: A Systematic Review on Microbial Imbalances and Diagnostic Tools for Urinary Disorders.
    Sara Palumbo, Giuseppe Lucarelli, Francesco Lasorsa, Rocco Damiano, Riccardo Autorino, Achille Aveta, Gianluca Spena, Sisto Perdonà, Pierluigi Russo, Carlo Giulioni, Angelo Cafarelli, Marco Finati, Salvatore Siracusano, Savio Domenico Pandolfo (2025) - Urology
  19. Lactobacillus crispatus-dominated vaginal microbiome and Acinetobacter-dominated seminal microbiome support beneficial ART outcome.
    Kairi Koort, Kristiina Sõsa, Silver Türk, Eleri Lapp, Elle Talving, Peeter Karits, Karin Rosenstein, Madis Jaagura, Aire Sekavin, Deniss Sõritsa, Kai Haldre, Helle Karro, Paul Korrovits, Andres Salumets, Reet Mändar (2023) - Acta obstetricia et gynecologica Scandinavica
  20. Cervicovaginal Microbiome: Physiology, Age-Related Changes, and Protective Role Against Human Papillomavirus Infection
    Diana Alizhan, Talshyn Ukybassova, Gauri Bapayeva, Gulzhanat Aimagambetova, Kuralay Kongrtay (2025)


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