Megaspheara species

Megasphaera bacteria (type 1 and type 2) are highly associated with bacterial vaginosis, and in one study using PCR testing, were found in higher concentrations (up to five times more) in those with BV than those without.

Megasphaera are gram-negative anaerobic bacteria, part of Clostridia genus.

Oxygen is toxic to these bacteria. Some notable other Clostridia species include those that produce serious toxins, including tetanus (C. tetani) and botulinum toxin (C. botulinum), used as a neuromodulator cosmetic injection (like Botox).

Megasphaera is an unculturable bacteria and can only be found using DNA/RNA (PCR) testing techniques. Megasphaera are lactic-acid producing bacteria, so may be considered part of a healthy environment by lowering the local pH to make it more acidic.

Some Megasphaera species may be unique to the vaginal environment and be an indicator, not necessarily a cause, of vaginal flora imbalances or infections.

Megasphaera species are also found in the mouth, and are not thought to be pathogens, but exist with other bacteria in a colony. These bacteria can adhere to cells, but virulence genes have not been identified.

In plain English, this means it survives where it can, but isn’t likely to be driving your BV by itself. Clostridia are a class of Firmicutes.

Firmicutes are so named because they have strong cell walls (firmus = strong, cutis = skin), with most Firmicutes having a gram-positive cell wall, but in the case of Megasphaera and a few others, the porous outer membrane causes them to stain gram-negative.


  • Marconi, Camila; Donders, Gilbert G; Parada, Cristina M G L; Giraldo, Paulo C da Silva, Marcia Guimarães.Do Atopobium vaginae, Megasphaera sp. and Leptotrichia sp. change the local innate immune response and sialidase activity in bacterial vaginosis?  Sexually Transmitted Infections; London Vol. 89, Iss. 2, (Mar 2013): 167.
  • Zozaya-Hinchliffe M, Martin DH, Ferris MJ. Prevalence and Abundance of Uncultivated Megasphaera-Like Bacteria in the Human Vaginal EnvironmentApplied and Environmental Microbiology. 2008;74(5):1656-1659. doi:10.1128/AEM.02127-07.

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Jessica Lloyd - Vulvovaginal Specialist Naturopathic Practitioner, BHSc(N)

Jessica is a degree-qualified naturopath (BHSc) specialising in vulvovaginal health and disease, based in Melbourne, Australia.

Jessica is the owner and lead naturopath of My Vagina, and is a member of the:

  • International Society for the Study of Vulvovaginal Disease (ISSVD)
  • International Society for the Study of Women's Sexual Health (ISSWSH)
  • National Vulvodynia Association (NVA) Australia
  • New Zealand Vulvovaginal Society (ANZVS)
  • Australian Traditional Medicine Society (ATMS)