One of the remarkable aspects of the vaginal microbiome is just how varied it can be from one person to the next. Clinically, we know what bacteria and organisms tend to be linked to infections or imbalance. But a healthy vaginal microbiome can present in several different ways. To make sense of this variety, researchers created broad categories of microbiome types. That way, once you take a vaginal microbiome test, you can take a look to see where you land and what that might mean for your health.
What Are Vaginal Microbiome Community State Types (CSTs)
Back in 2011, a study looked at the vaginal microbiome of 396 symptom-free North American women from four ethnic groups (white, black, Hispanic and Asian). Researchers sorted these vaginal microbiomes into five groups or vaginal community state types (CSTs). They even broke some into subgroups — just to keep things interesting.
Here’s a snapshot of those groups:
| Community State Type (CST) | Dominant Species | Other NOtes |
| CST I | Lactobacillus crispatus | Most healthy and stable |
| CST II | Lactobacillus gasseri | Healthy, stable |
| CST III | Lactobacillus iners | Healthy, less stable |
| CST IV | Diverse bacteria with low Lactobacillus | May be linked with BV |
| CST V | Lactobacillus jensenii | Healthy, stable |
Meet Vaginal CSTs, II, and V: The Stable Types
These microbiomes are more stable because their main bacteria — Lactobacillus — is protective. Around 80 percent of Asian and 90% of white women in the study had one of these types. They were also found in Hispanic and Black women but less frequently (60%). Even though these CSTs are considered “healthy,” that doesn’t rule out the possible imbalances or the need for treatment — especially if you have symptoms.
Vaginal CST III: Healthy, But Less Stable
Type III is dominated by L. iners which make L- lactic acid. This acid is not quite as good at warding off harmful bacteria as D- lactic acid (produced by other lactobacilli species). This CST is a little less protective against bacterial vaginosis (BV) and is considered a “transitional state” between a healthy vaginal microbiome and one with conditions like BV.
One last note about this state type: type III is further divided into two additional categories; III-A and III-B. III-A has a higher amount of L. iners, whereas III-B has less L. iners, and more diverse bacteria. How is this helpful? III-A is considered to be more stable and III-B has a higher risk of developing BV.
Vaginal CST IV: The Complicated One
Type IV is by far the trickiest to define. It’s made up of a mix of bacteria rather than being dominated by any one species. Interestingly, this type can be perfectly healthy, especially in the absence of any symptoms.
CST Type IV microbiomes tend to have higher levels of certain anaerobic bacteria (which grow without oxygen) including Prevotella, Dialister, Atopobium and others.
Type IV community state types are divided into further subcategories depending on the predominant type of bacteria present.
| CST IV subgroup | General Features |
| IV-A | High to moderate abundance of BVAB1 and G. vaginalis |
| IV-B | High to moderate abundance of G. vaginalis and A. vaginae |
| IV-C0 | Dominated by Prevotella spp. |
| IV-C1 | Dominated by Streptococcus spp. |
| IV-C2 | Dominated by Enterococcus spp. |
| IV-C3 | Dominated by Bifidobacterium spp. |
| IV-C4 | Dominated by Staphylococcus spp. |
About 25 percent of women have this type of microbiome, and many have no symptoms! They do often have a higher pH than women with other community state types. However, their vaginal microbiomes are not necessarily in or on their way to becoming an unbalanced state associated with, say BV.
Can Your CST Change?
Yes! Your community state type isn’t set in stone. Hormonal factors, your period, sexual activity and antibiotics can shift the balance. For example, L. iners (associated with CST IV) might dominate during your period, temporarily replacing a more protective type like L. crispatus (CST I). Antibiotics can also wipe out all bacteria in the vagina — good and bad — sometimes leading to yeast infections.
Using Vaginal Microbiome CSTs to Guide Your Health Care Choices
The vaginal microbiome is a complex ecosystem. While Lactobacillus-dominated communities are associated with good vaginal health, the diversity of other types — especially CST IV — shows there’s no one “perfect” pattern.
Further research is needed to fully understand the significance of these diverse communities and their potential impact on vaginal health. But knowing your current community state type can give insight into your current vaginal health, help explain certain symptoms or recurring infections, and guide discussions with your healthcare provider.
Sources
Ravel, J., Gajer, P., Abdo, Z., Schneider, G. M., Koenig, S. S., McCulle, S. L., Karlebach, S., Gorle, R., Russell, J., Tacket, C. O., Brotman, R. M., Davis, C. C., Ault, K., Peralta, L., & Forney, L. J. (2011). Vaginal microbiome of reproductive-age women. Proceedings of the National Academy of Sciences of the United States of America, 108 Suppl 1(Suppl 1), 4680–4687.
De Seta, F., Campisciano, G., Zanotta, N., Ricci, G.I say , & Comar, M. (2019). The Vaginal Community State Types Microbiome-Immune Network as Key Factor for Bacterial Vaginosis and Aerobic Vaginitis. Frontiers in microbiology, 10, 2451.
Brooks, J. P., Buck, G. A., Chen, G., Diao, L., Edwards, D. J., Fettweis, J. M., Huzurbazar, S., Rakitin, A., Satten, G. A., Smirnova, E., Waks, Z., Wright, M. L., Yanover, C., & Zhou, Y. H. (2017). Changes in vaginal community state types reflect major shifts in the microbiome. Microbial ecology in health and disease, 28(1), 1303265.
