Exploring Vaginal Microbiome CSTs: A Guide

While each vaginal microbiome is distinctive, recent studies have categorised them into five general groups, often referred to as Community State Types (CSTs)¹.

As research in this area progresses, understanding these vaginal microbiome CSTs can provide valuable insights into your vaginal microbiome’s composition, potential symptoms, and the risk of infections such as bacterial vaginosis (BV) or aerobic vaginitis (AV).

The primary distinguishing factor among these vaginal microbiome community state types is the type and quantity of Lactobacillus bacteria, a pivotal component for many in maintaining vaginal microbiome health². Lactobacilli contribute to vaginal health in various ways³:

Regulating pH Levels: They produce lactic acid, a substance that helps maintain an optimal and healthy vaginal pH (ideally between 3.8 and 4.5)^2,3.
Occupying Space: Lactobacilli live on cells in the vagina, impeding the growth of harmful pathogens⁴.
Natural Antibiotics: They produce bacteriocins, which act as natural antibiotics⁴.
Reducing Inflammation: Lactobacilli help in reducing inflammation in the genital tract⁴.

Here’s a closer look at the five vaginal microbiome community state types:

Type 1 – L. crispatus

Type 1 is considered the healthiest⁵ as it has demonstrated the highest success in preventing infections such as BV, STIs⁶, and UTIs⁷. It also carries the lowest risk of other health complications like infertility⁸, preterm birth⁹, and toxic shock syndrome (TSS)¹⁰.

Lactobacillus crispatus is the key bacterium in Type 1, known to produce both L- and D-lactic acid, maintaining an acidic environment that prevents pathogen proliferation^11–13.

Type 1 includes two subtypes: Type 1-A and Type 1-B, differing mainly in the percentage of L. crispatus.

Type 2 – L. gasseri

This type is also considered healthy and is dominated by Lactobacillus gasseri. Like L. crispatus, L. gasseri produces D-lactic acid, although in slightly lower quantities^12,14.

Despite this, Type 2 exhibits robust protection against pathogens¹³ and a reduced risk of infections like BV¹³, UTIs¹⁵, and STIs¹⁶. It is also associated with a lower risk of health conditions such as infertility¹⁷, pelvic inflammatory disease¹⁸, neonatal issues¹⁹, and TSS²⁰.

Type 3 – L. iners

Dominated by Lactobacillus iners, Type 3 is characterised by versatility. While lactobacilli dominance is generally desired, L. iners can coexist many types of bacteria, making the microbiome more prone to shifting in and out of a healthy state.

When found alongside disruptive bacteria, it can cause symptoms like itching and abnormal discharge. However, in combination with protective lactobacilli, it appears to act neutrally or protectively. Type 3 offers some protection by occupying cells on the vaginal wall and producing L-lactic acid, which helps limit pathogen growth.

However, it is less effective at maintaining an acidic environment compared to other vaginal lactic acids, necessitating a higher number of L. iners to maintain a healthy pH balance.

Research also suggests that L. iners is less protective against STIs and pregnancy complications than other Lactobacillus species. Type 3 has two subtypes: 3-A and 3-B, with no clear distinction in protective capabilities between them.

Type 4 – non-lactobacilli

Characterised by a low presence of lactobacilli and a high diversity of other bacteria, Type 4 may indicate vaginal dysbiosis and an unstable vaginal environment, potentially leading to recurrent infections.

Studies have indicated that a high microbial diversity may elevate the risk of adverse health outcomes such as pregnancy complications, STIs, and pelvic inflammatory disease.

However, having a Type 4 result is not necessarily a cause for concern, as the vaginal microbiome is dynamic and can be influenced by various factors, including medications, supplements, and lifestyle choices.

Notably, not all Type 4 communities are harmful; some women with Type 4 microbiomes may also host protective bacteria like Bifidobacterium.

Furthermore, Type 4 has been subdivided into three subtypes based on the presence of specific bacteria proportions, each potentially associated with various health implications.

Type 5 – L. jensenii

This is considered a healthy vaginal community state type, characterized by domination by Lactobacillus jensenii. L. jensenii contributes to a protective and stable environment by occupying space on the vaginal wall and producing antimicrobial bacteriocins.

Similar to L. crispatus, L. jensenii produces D-lactic acid. Although relatively rare, it is one of the healthiest dominant strains, offering substantial protection against infections like BV, STIs, and UTIs.

Consequently, Type 5 is linked to a very low risk of related health problems (infertility, pelvic inflammatory disease, toxic shock syndrome, and others).

The significance of understanding vaginal microbiome types lies in their dynamic nature. Unlike static genetic results, vaginal microbiomes constantly change due to factors such as birth control, medications, supplements, sexual partners, and lifestyle choices. These changes can occur throughout life, from the very first period to pregnancy, postpartum, and post menopause.

Knowledge about your vaginal microbiome type empowers you to detect potential imbalances early, enabling proactive measures to promote protective bacteria and prevent disruptive ones from taking hold. To discover your classification and complete microbial composition, get an at-home comprehensive vaginal microbiome test.

References

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