What is Lactobacillus crispatus?
Lactobacillus crispatus is a beneficial bacterial species that naturally dominates the healthy vaginal microbiota and serves as the primary defense mechanism against urogenital infections through production of lactic acid and antimicrobial compounds. 1
Primary Biological Role
L. crispatus is the most prevalent and protective Lactobacillus species in healthy cervicovaginal microbiota, producing copious amounts of lactic acid that functions as a potent broad-spectrum bactericide, virucide, and immunomodulator. 1 This species is considered an important microbial biomarker of vaginal health due to its professed beneficial implications. 2
Mechanism of Protection
The protective effects of L. crispatus operate through multiple pathways:
Direct antimicrobial activity: L. crispatus produces antimicrobial compounds including lactic acid and secreted S-layer proteins that demonstrate pH-dependent activity against common vaginal pathogens including Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, Streptococcus agalactiae, Enterococcus faecalis, and Candida albicans. 3
Competitive exclusion: Live L. crispatus cells strongly reduce adhesion of pathogenic strains, particularly Candida albicans, in adherence assays. 4
Immune modulation: The exopolysaccharide produced by L. crispatus induces higher expression of human defensin HBD-2 in vaginal cells, which correlates with pathogen growth inhibition. 4
Clinical Significance vs. Other Lactobacillus Species
L. crispatus is superior to L. iners for vaginal protection. Following standard metronidazole treatment for bacterial vaginosis, L. iners typically becomes the dominant species, which likely contributes to the high recurrence rates (50-80% within one year) seen with bacterial vaginosis. 5 The selection of L. crispatus over L. iners for probiotic development reflects the understanding that natural predominance does not equal protective capacity. 5
Therapeutic Applications
Vaginal suppositories containing L. crispatus CTV-05 showed the best efficacy in clinical trials for preventing recurrent urogenital infections. 6 In a high-quality RCT (1b evidence), high-level colonization with L. crispatus in the treatment group was associated with UTI risk reduction (RR 0.7, p <0.01). 7
Route of Administration Matters
Vaginal administration is more effective than oral: The use of cell-free supernatant (CFS) from L. crispatus may be more efficient than actively replicating bacteria, as oral administration of live L. crispatus may result in treatment failure. 3
Oral administration can colonize the vagina: Recent evidence shows that L. crispatus NTCVAG04 administered orally can colonize both the gut and vagina, with 75% of women showing positive rectal swabs and most also having positive vaginal swabs after two 14-day courses. 8
Strain-Specific Variability
Not all L. crispatus strains are equivalent. Even phylogenetically closely related L. crispatus strains possess unique features in terms of their antimicrobial activities and competitive abilities, suggesting they exert marked competition and evolutionary pressure within their specific environmental niche. 2 This highlights the importance of using clinically validated strains rather than generic "L. crispatus" products. 6
Common Pitfalls
Avoid generic products: Do not use generic "Lactobacillus" products without strain specification—the specific strain L. crispatus CTV-05 has the best evidence for vaginal health. 6
pH testing limitations: Vaginal pH testing alone cannot distinguish between protective L. crispatus-dominated and less protective L. iners-dominated communities, as both can maintain acidic pH. 5
Recognize production mechanisms: The antimicrobial activity of L. crispatus is mediated by both lactic acid production and secreted proteins, with the cell-free supernatant showing greater antimicrobial efficacy than live cells in some contexts. 3