An infection that affects one in three women and often comes back after treatment can be wiped out in many cases if their male partner is treated too.
That’s according to an Australian clinical trial which also found the condition, called bacterial vaginosis or BV, can be sexually transmitted — a controversial idea in sexual health circles.
The trial results make “the first inroads into improving cure for women through reducing [BV] reinfection and recurrence”, according to study co-author Catriona Bradshaw, a sexual health physician at Melbourne’s Alfred Health and researcher at Monash University.
The research was unveiled today in the New England Journal of Medicine.
The Burnet Institute’s Gilda Tachedjian, who has collaborated with Professor Bradshaw in the past but was not involved in the new research, called it a “landmark” study.
“It’s a really important proof of concept that BV recurrence is driven, in part, by transfer of bacteria from the male to the female,” Professor Tachedjian said.
“That is going to rewrite textbooks.“
But it will likely be some time, perhaps years, before the treatment regimen is available in clinics.
From anecdotal to scientific evidence
While some people with BV are asymptomatic, the most common signs of the condition are a thin, watery discharge and a fishy odour “which can cause enormous distress”, Professor Bradshaw said.
Most people do not go on to have serious complications, but BV can also increase someone’s risk of:
- catching and transmitting sexually transmitted infections
- pelvic inflammatory disease
- miscarriage
- premature birth
- low birth weight.
Unlike chlamydia and gonorrhoea, which are caused by specific bacteria species, BV occurs when the balance between different species of vagina-dwelling microbes is thrown out of whack.
For many people with BV, this “microbiome disorder” appears after sex with a new partner. Sometimes they can clear the condition on their own, while others are treated with a course of broad-spectrum antibiotics.
“But all antimicrobial therapy is solely directed at the woman with the infection to treat her infection,”
Professor Bradshaw said.
And BV often returns within a few months after treatment.
There were a few theories as to why it might recur. BV-causing bacteria are thought to hide under protective “biofilm” shields, away from the killing actions of antibiotics, only to re-emerge and reinfect down the track.
A person might increase their risk of BV relapse by using douches, or by having unprotected sex. Semen can change the vaginal environment, making it more hospitable to certain bacteria.
But according to medical orthodoxy in the early 2000s, BV-linked bacteria could not be directly passed from penis to vagina.
Professor Bradshaw, then working as a doctor at a sexual health centre in Melbourne, believed otherwise.
“There was a lot of evidence clinically and anecdotally that BV was being acquired from new partners, and recurrence was being driven by ongoing exposure to untreated partners,” Professor Bradshaw said.
So over the next couple of decades, she and others found people in Melbourne who tended to get recurrent BV weren’t traditionally considered “high risk” — from, for example, having lots of different sexual partners — but were in heterosexual monogamous relationships.
Another study found people who had penile-vaginal sex had “all the BV”, while those who had never had any kind of sex had no BV.
So it appeared to Professor Bradshaw that the penis, and its microbiome, played a role in at least some instances of BV.
This was bolstered by male circumcision trials in Central Africa which found female partners of circumcised men had less BV than those who had sex with uncircumcised men.
Compared to circumcised men, uncircumcised men usually have a more diverse penis microbiome, including the kinds of bacteria that take over the vagina in BV.
“I started to think about interventions that may address carriage of BV bugs in men under the foreskin as well as inside the urethra,”
Professor Bradshaw said.
And, she figured, wiping out those bugs with antibiotics could cut BV recurrence.
BV partner-treatment trial stopped early
Professor Bradshaw wasn’t the first to link penises with BV. Trials back in the 1980s treated BV-infected women and their male partners with oral antibiotics.
The idea was if he (and his penis) was responsible for reinfecting her, the tablets should clear everything up.
But it didn’t work. For many women in the trial, the condition returned, so scientists all but ruled out the role of penile bugs in BV recurrence.
So Professor Bradshaw and her colleagues designed a partner treatment trial to treat men with oral and topical antibiotics — to better target any bacteria lurking in the penis’s nooks and crannies — while their female partner was being treated with the usual recommended antibiotics.
Catriona Bradshaw (L) and Lenka Vodstrcil led the new study. (Supplied: Melbourne Sexual Health Centre)
They started enlisting heterosexual monogamous couples to the trial in 2019 and randomly assigned them to the intervention group, where both partners were treated, or the control group, where only the woman was treated.
They planned to recruit 350 couples, but stopped the trial after around 160. Not because the treatment wasn’t working, but because it worked incredibly well.
By 12 weeks after treatment, BV was back in 63 per cent of women in the control group.
For their counterparts in the partner-treatment group, though, recurrence rate was just 35 per cent.
Professor Bradshaw and her team are turning attention to why BV stubbornly persists in some people, even if their partner undergoes the full course of treatment too.
It may be partly due to the presence of an intrauterine device, or IUD. The strings that hang down into the vagina can harbour bacterial biofilms.
The makeup of the rest of the vaginal microbiome could also affect BV recurrence, as might how well a partner adhered to their treatment regime.
Will it change the way BV is treated?
Clare Keogh, a sexual health doctor at SHINE SA who was not involved in the study, called the trial “promising” but said it would not change clinical practice at this stage.
“We don’t have enough evidence to change guidelines currently, but also … with the ointment being used twice a day [plus oral antibiotics] for the partner with the penis, how long is that adherence or compliance likely to continue for?
“Further feeding into the compliance issue, if you’re not the person affected by the condition, you’re less likely to be compliant with the treatment regimen.“
Professor Bradshaw acknowledged these buy-in issues. Recruiting men for the study “was really difficult”, she said.
Of the men who did participate in the antibiotics intervention group, one in seven later reported they took less than 70 per cent of their medication during the trial.
To expand findings beyond monogamous heterosexual couples, the study should be repeated in other groups, including women who have sex with other women, and a range of cultural and ethnic groups, Professor Tachedjian added: “It will help change policy and practice as well, in particular contexts.”
Professor Bradshaw hopes national BV treatment guidelines do eventually change to incorporate partner treatment.
“You can’t change guidelines until you have rock-solid evidence with very, very strong effect sizes,” she said.
In the meantime, should “bacterial vaginosis” be renamed?
Professor Bradshaw thinks so: “It needs a new name and this is part of the problem, because — as one of our male partners eloquently said — [BV] is a shared responsibility.”