The vaginal microbiota is one of the most specific and best-characterized human microbiomes. Its composition directly influences intimate comfort, protection against infections, and reproductive health. Science now classifies it into several distinct types (CST—Community State Types), each with a different risk of dysbiosis. Explore our range of products for vaginal health and intimate comfort.
What Are the Types of Vaginal Microbiome (CST)?
The CST (Community State Types) classification identifies five major types of vaginal microbiome—a major breakthrough in vaginal microbiome research.
- CST I: Dominance of Lactobacillus crispatus —the most protective type, very acidic pH (3.5–4.0), lower risk of bacterial vaginosis and infections
- CST II: dominated by Lactobacillus gasseri —intermediate protection
- CST III: Dominance of Lactobacillus iners —the most unstable type, which can rapidly shift toward bacterial vaginosis
- CST IV: Diverse microbiome without lactobacilli dominance—the type most strongly associated with bacterial vaginosis, infections, and increased risk of STI transmission
- CST V: Dominance of Lactobacillus jensenii — protection similar to CST I
- CST composition varies by ethnicity, hormones, sexual behavior, and diet
L. crispatus vs. L. iners: What’s the difference?
The two dominant Lactobacillus species have very different protective properties.
- L. crispatus: produces two types of lactic acid (D and L) + hydrogen peroxide — optimal chemical barrier against Candida, anaerobic bacteria associated with vaginosis, and E. coli associated with cystitis
- L. iners: produces only L-lactic acid, no H₂O₂ — less effective protection, likely to disappear quickly during disruptions (sexual intercourse, antibiotics, menstruation)
- A microbiome dominated by L. crispatus (CST I) is the target of probiotic interventions for vaginal health
- Probiotics containing L. rhamnosus GR-1 + L. reuteri RC-14 have demonstrated the ability to restore L. crispatus when taken orally
Vaginal microbiota and reproductive health?
The composition of the vaginal microbiome directly influences reproductive health—a link that is increasingly well-documented.
- Fertility: A microbiome dominated by L. crispatus is associated with higher success rates in IVF (in vitro fertilization)—couples undergoing assisted reproductive technology (ART) benefit from a vaginal microbiome assessment
- Pregnancy: Untreated bacterial vaginosis is associated with an increased risk of premature rupture of membranes and preterm birth—screening and treatment are essential
- Neonatal transmission: the vaginal microbiome (ideal CST I) seeds the infant’s gut microbiome during vaginal delivery
- STIs (sexually transmitted infections): CST IV (without lactobacilli dominance) increases susceptibility to HPV, HIV, and Chlamydia
Diagnostic tests for the vaginal microbiota?
Diagnostic tools can objectively assess the composition of the vaginal microbiome and guide interventions.
- Vaginal pH: the most accessible test—pH strips available at pharmacies; pH < 4,5 : microbiome lactobacillaire sain ; pH > 4.5: suspected bacterial vaginosis
- Amines test (Whiff test): addition of KOH to secretions—fishy odor = confirmed bacterial vaginosis
- Metagenomic analysis of vaginal secretions: species mapping, CST classification—available in a laboratory by prescription or as a direct-to-consumer kit
- Pap smear: may reveal the presence of Gardnerella vaginalis (an indicator of vaginosis)—as part of routine gynecological follow-up
- Results should always be interpreted with a gynecologist or primary care physician
Probiotics and support for the vaginal microbiota?
Probiotic approaches for the vaginal microbiota follow two complementary pathways.
- Oral route (L. rhamnosus GR-1 + L. reuteri RC-14): vaginal colonization via the intestinal–perineal route — documented in several RCTs; systemic effect on the entire urogenital tract
- Local vaginal route (ovules, capsules): direct action at the site, rapid restoration of pH—see vaginal gels
- After antibiotic therapy: period of highest risk of imbalance— lactic acid bacteria starting on the first day, 1-month course
- During menopause: intimate care and local probiotics support the mucosa in the absence of estrogen
- See also our urinary comfort line—documented link between the vaginal microbiome and cystitis prevention
