‘Paradigm shift': Australian researchers discover key to treatment of bacterial vaginosis

The Guardian

05-03-2025

Like almost one in three women, Hanae has developed bacterial vaginosis (BV) – a condition when the normal healthy bacteria in the vagina are replaced by an overgrowth of other mixed bacteria.
When she got it for first time in 2021, she took the standard treatment of antibiotics, only for the condition to come back weeks later. 'It came back time and time again, no matter how many times I got antibiotic treatment,' said Hanae, who lives in Melbourne.
'I thought there was something wrong with me.'
The BV came back roughly every three months, affecting her confidence and the relationship she was in at the time, 'creating a barrier between us'.
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Hanae and her current partner were part of a new study, which has found BV is sexually transmitted between partners – despite not being classified as a sexually transmitted disease.
The study, published in the New England Journal of Medicine alongside an editorial, showed there is more than double the rate of women being cured of BV if their male partner is treated at the same time.
Researchers had thought BV was an STI years ago, but a number of trials in the 80s and 90s did not find treating a man alongside his female partner was effective.
Prof Catriona Bradshaw, of Monash University's Melbourne Sexual Health Centre said those studies were taken 'as very conclusive evidence that bacterial vaginosis wasn't sexually transmitted'.
'The key thing is that all previous trials had only tried oral antibiotics, and oral antibiotics should work quite well for BV bugs inside the urethra, but no one had tried a topical antibiotic on the skin to also get rid of the bugs on the skin of the penis.
'This was our hypothesis.'
Bradshaw together with her colleagues at Monash University and Alfred Health studied 164 monogamous heterosexual couples where the pre-menopausal woman had BV. The trial ran from April 2019 through November 2023 across two sexual health services and three family-planning services in three states.
The couples were randomly assigned to two groups – one where both the male and female partner were treated, and one control group where only the female partner received treatment.
The researchers ensured there was equal representation in each group of women using an intrauterine device (IUD) and uncircumcised males – both of which have been linked with an increased risk of BV.
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Women in each group received the same treatment of oral antibiotics, while men in the partner treatment group received oral antibiotics taken twice daily for seven days, and an anti-bacterial cream over that period.
Researchers then followed up with the couples regularly for 12 weeks to establish how effective their intervention was in curing BV.
BV recurred in 24 of 69 women (35%) in the partner-treatment group, and in 43 of 68 women (63%) in the control group.
Bradshaw said the results of the study are 'a big paradigm shift. It's proven sexual transmission of BV.'
Bradshaw acknowledges that while reinfection with BV bacteria from male partners may be responsible for recurrence in many women, there were some women who weren't cured.
Antibiotics might not have worked for women with a dense biofilm – the biological tissue of the vaginal microbiome – or with an IUD, which the bacteria coats, making it harder for antibiotics to clear, Bradshaw said.
Further strategies need to be developed for these women, such as a longer courses of antibiotics, she said.
The editorial also noted that 14% of the men in the intervention group reported taking less than 70% of their prescribed doses of medication, 'an early signal that male partner buy-in could be challenging in some situations'.
Bradshaw said that the cure rates in women whose male partners were 100% adherent to the tablets and the cream were far higher.
The authors acknowledged a limitation of the study was that the participants largely included people attending sexual health centres, which may reflect a higher-risk population.
Prof Rebecca Guy from the Kirby Institute's Sexual Health Program said this was the 'first study to show sustained and substantial benefit for a common and debilitating vaginal infection'.
'It also provides evidence for sexual transmission of the bacteria that causes bacterial vaginosis.'
Guy said the findings will inform clinical guidelines and new clinical protocols on treatment of the condition. 'Success will rely on strategies to ensure high treatment cooperation rates among male partners, as achieved in the trial.'