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Experts debate what makes a healthy vagina

News analysis New US findings suggest our accepted definition of a healthy vagina could be ethnically biased, say some researchers, but others caution against over-interpreting the data.

A new study published today in Science Translational Medicine found, what an accompanying commentary describes as, an "unexpected and astonishing" variability over time in the vaginal bacterial communities of apparently healthy women.

It is commonly accepted that a vagina with a high proportion of lactobacilli bacteria is healthy, and one with a low number is less healthy.

One common test diagnoses a condition called bacterial vaginosis (BV) on the basis of a low lactobacilli count.

But the new study questions this simple view. It examined vaginal bacteria twice a week over 16 weeks in 32 apparently healthy women of reproductive age.

It found that women differ greatly in their vaginal bacterial profiles over time. In some women the profile changes only during menstruation, while in others there was little or no change during menstruation. Still others had frequent changes that were independent of the reproductive cycle.

And the study found the vaginas of Caucasian women were more likely to be dominated by lactobacilli, than those of African-American women, some of whom could be diagnosed as having BV.

"This study ... signals the death knell of the still widely accepted statement that healthy vaginal communities must contain a high proportion of lactobacilli," write the authors of an accompanying commentary, Drs Steven Witkin and William Ledger of Weill Cornell Medical College.

"Because the earliest studies that attempted to characterise bacterial biotypes in the vagina were performed on white women, it is interesting to ponder whether the widespread acceptance of lactobacilli as being essential for a 'normal' vagina has an ethnic bias."

Caution urged

But an Australian expert in bacterial vaginosis warns against over-interpreting the findings of the new study.

Associate Professor Catriona Bradshaw, of the University of Melbourne and The Alfred Hospital, describes the study as "really important" because it shows the variability in vaginal bacterial communities in women over time and the influence of factors such as menses and sex.

But, says Bradshaw, there is a lot of data to show the acidic environment produced by lactobacilli is protective against BV. She says BV is linked to an increased risk of acquiring HIV and sexually transmissable infections, and having a premature baby and miscarriage.

Bradshaw says the new study is too short to say whether the women whose bacterial flora is less likely to be dominated by lactobacilli are also protected from these negative outcomes in the long term.

She says in the US, 1 in 3, mainly African-American and Hispanic, women are diagnosed with BV and this could reflect those groups' poor access to healthcare. By contrast, she says, the rate of diagnosis in Australia is 1 in 10.

Nevertheless, says Bradshaw, 50 per cent of women with a BV diagnosis don't have any symptoms of an abnormal discharge or odour, and it is fair to question whether all these women are indeed unhealthy.

What is 'normal'?

One of the authors of the new study, microbial ecologist Professor Larry Forney, of the University of Idaho agrees that socio-economic factors could explain the differences in ethnic groups.

He also agrees it's not clear what the health outcomes of the women with low lactobacilli numbers will be in the long term.

But, says Forney, the fact that women can make transitions between different bacterial profiles so often raises questions over what should be regarded as normal.

High proportions of lactobacilli may be associated with healthy vaginas, but Forney says it would be a "logical fallacy" to assume the absence of high levels of lactobacilli means a woman is unhealthy.

He says vaginal acidity can be preserved despite a changing bacterial profile because lactic acid is produced by species other than lactobacilli.

Talking vaginas

One thing everyone seems agreed on: vaginal bacterial flora is less stable and more varied that traditionally thought.

And we have to be very careful about drawing conclusions on the health of a woman's vagina by a test at a single point in time.

Forney and colleagues' research emphasises the complexity of the problem as researchers strive to understand what triggers fluctuations in the vagina's flora and what kind of fluctuations can lead to problematic BV.

And then there's the question of how to treat BV symptoms.

While antibiotics are used they often don't work and there is insufficient evidence to support the effectiveness of such things as probiotics and yoghurt douches, says Bradshaw.

The challenge for researchers is even greater, says Forney, because women are reluctant to talk about the issue - with each other, to their partners or even their doctors.

"People don't want to talk about vaginas," he says.