AV and CV: Why the Vaginal Microbiome Switches

Author: Jessica Lloyd
Senior Vulvovaginal Specialist Naturopath | BHSc(N) | ISSVD, ISSWSH, BSSM, ATMS

Last reviewed: July 30, 2026

There is a vaginal microbiome scenario with swift switches between aerobic vaginitis (AV) and cytolytic vaginosis (CV) related bacteria as dominant.^1,2

The vaginal microbiome goes from being dominated by AV-associated bacteria such as Escherichia coli and Enterococcus faecalis to a very high proportion of (usually) Lactobacillus crispatus, from 98 per cent or greater.

CV is very specific, and CV and AV may switch back and forth many times after various treatments.

Understanding CV – what it is and isn’t

If, for example, there was 98 per cent of L. iners, at My Vagina, we would not consider this the same sort of CV (read more about L. iners dominant flora). It is very specifically L. crispatus in this AV-CV scenario, possibly L. gasseri or L. jensenii, but they are much less common.

L. iners can cause inflammation and damage cells, but L. iners isn’t a good lactic acid producer, and the circumstances whereby AV and CV switch don’t apply to L. iners. It’s not the same cause.

Dominance of L. crispatus – do I have CV?

Vaginal dominance of L. crispatus by itself is not a diagnosis of CV and may be healthy in the absence of symptoms.³

If a comprehensive vaginal microbiome test or your doctor determines using microscopy that you have a high number of lactobacilli present, and you have CV symptoms, a diagnosis may be made.

Determining CV relies on the presence of matching symptoms, and a high amount on a test result alone is not definitive. Do not self-diagnose CV! It is a very specific condition.

Matching symptoms of AV and CV

In this switching of AV and CV, the symptoms often stay the same, which can be confusing. But both conditions cause inflammation and will tend to have a pH within the normal range (3.8-4.5). You may treat the AV with antibiotics, then find it’s switched to CV, but you feel more or less the same. This is common.⁴

Symptoms of CV

Burning
Irritation
Itching
Thick or stringy white discharge

Symptoms of AV

Burning
Irritation
Itching
Yellow-green discharge
Foul odour

Why does the microbiome switch between AV and CV?

The presentation of AV and then CV (and vice versa) is a symptom picture that gives us a lot of clues. The vaginal cells offer a safe harbour only to certain types of bacteria (L. crispatus, E. coli, E. faecalis), and that’s why they can switch back and forth in this very specific way.

While the bacteria are most likely causing your vaginal symptoms, they are not the underlying problem – they are just a symptom of a bigger systemic issue that needs addressing.

This underlying problem, not just the vaginal microbiome, must be corrected, or treatment will continue to fail. See a My Vagina practitioner, and if you haven’t already, get a comprehensive vaginal microbiome test.

Frequently asked questions

What is the difference between AV and CV?

Aerobic vaginitis (AV) is an overgrowth of aerobic bacteria like E. coli and E. faecalis, often with yellow-green discharge and odour. Cytolytic vaginosis (CV) is an overgrowth of lactobacilli (usually L. crispatus) that damages vaginal cells, with thick white discharge. Both cause burning, itching and irritation.

Why do AV and CV keep switching?

In some people the vaginal cells seem to shelter only a few specific bacteria – L. crispatus, E. coli and E. faecalis – so the microbiome can flip between an AV-dominant and a CV-dominant state, especially after treatment. The symptoms often stay similar, which is confusing.

How do I know if I have CV or AV?

You cannot reliably tell them apart by symptoms alone, and you should not self-diagnose CV. It needs matching symptoms plus testing – microscopy or a comprehensive microbiome test showing very high lactobacilli for CV, or aerobic bacteria for AV. Getting the right diagnosis matters, because the treatments differ.

Can too much lactobacillus be a bad thing?

Yes – that is essentially what cytolytic vaginosis is. While lactobacilli are usually protective, an extreme overgrowth of L. crispatus can over-acidify and damage vaginal cells, causing symptoms. More is not always better when it comes to the vaginal microbiome.

This article is general information, not medical advice. AV and CV are specific conditions that can look alike and can switch back and forth, so please do not self-diagnose – treating the wrong one (for example, taking antibiotics for CV) can make things worse. See a doctor or an experienced practitioner, ideally with a comprehensive microbiome test, and address any underlying issues rather than just the microbes.

Donders GGG, Bellen G, Grinceviciene S, Ruban K, Vieira-Baptista P. Aerobic vaginitis: no longer a stranger. Research in Microbiology. 2017;168(9-10):845–858.
Cibley LJ, Cibley LJ. Cytolytic vaginosis. American Journal of Obstetrics and Gynecology. 1991;165(4):1245–1249.
Bhat R, Suresh A, Rajesh A, Rai Y. Cytolytic vaginosis: A review. Indian Journal of Sexually Transmitted Diseases and AIDS. 2009;30(1):48.
Tempera G, Furneri PM. Management of Aerobic Vaginitis. Gynecologic and Obstetric Investigation. 2010;70(4):244–249.