Your vagina teems with live microbes. They are as unique to you as skin or hair color. They are far more important though. These microbes are the map behind many facets of reproductive health.

Unfortunately, not much attention is paid until they cause trouble as in itching or oozing. Science is finding that certain mixes of microbes are linked with problems like vaginosis and sexually transmitted diseases. Pathogens are more likely to spread when specific microbes are present or absent.

So what is normal exactly? And is this “normal” considered healthy or optimum for women?

No itching, no discharge, no infections, in other words — no symptoms; this is the baseline for a “healthy” vaginal microbiota (VMB). The species that predominates in many healthy women — who are not pregnant — is Lactobacillus.

These species are thought to play key protective roles by:

  • Lowering pH through lactic acid production
  • Generating various compounds including hydrogen peroxide and bacteriocins
  • Competing with pathogens by building barriers to prevent their colonization and adherence

Lactic acid is the star in normal VMB. As the name states, it’s an acid, so if you can recall from high school chemistry class, pH drops down. Good microbes thrive.

A low (acidic) pH is not what pathogens like. The bad guys which induce vaginosis shrivel up and die.  Researchers believe that this acidic environment is also inhospitable to the scourge called human immunodeficiency virus (HIV) as well as sexually transmitted diseases—no picnic either– including gonorrhea, Chlamydia and herpes simplex.

Now this is where the characterization of “normal” gets really remarkable.

Different women, different microbes

No core VMB exists for all women. Race matters. Analysis of vaginal microbiota of white, black, Hispanic and Asian women reveals big differences.

Jacque Ravel and colleagues conducted interesting research with 396 asymptomatic North American women who represented four ethnic groups (white, black, Hispanic, and Asian) who were sampled and then species composition was identified by barcoded 16S rRNA genes. Vaginal microbiome of reproductive-age women appeared in Proceedings of National Academy of Sciences USA.  

The details:

The VMB are graded I, II, III, IV and V, according to which community groups dominate. For example, the researchers found:

  • Grade I is dominated by Lactobacillus crispatus (in 26% of sample)
  • Grade II: Lactobacillus gasseri (6%)
  • Grade III: Lactobacillus iners (34%)
  • Grade V: Lactobacillus jenseii (5%)

These four main groups were isolated primarily from White and Asian women.

What happened to Grade IV?

As you may surmise, that group was found mainly in Black and Hispanic women. Grade IV was not dominated by Lactobacillus. Instead organisms including Gardnerella, Pretovella, Corynebacterium, Atopobium, Megasphaera and Sneathia were found.

This distinction is striking, and important. Differences in microbial composition may radically influence how vaginal communities respond to infections or other imbalances.

“The inherent differences within and between women in different ethnic groups strongly argues for a more refined definition of the kinds of bacterial communities normally found in healthy women and the need to appreciate differences between individuals so they can be taken into account in risk assessment and disease diagnosis.”

Now what?

How this plays out when clinical practice begins to incorporate microbe manipulation to prevent and treat disease should be interesting. Meanwhile, respect your unique microbes and stay tuned.