Treating Bacterial Vaginosis as an STI Could Improve Outcomes
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Research suggests that anywhere from roughly a quarter to more than a third of people with a vagina will contract bacterial vaginosis, or BV, at least once in their lifetimes. It involves an imbalance in the microbes that grow in the vagina, with pathogenic strains beating out healthier bacteria. It's not usually a serious condition, but it can put people at higher risk for contracting HIV and other sexually transmitted infections.

Now, some researchers are arguing that BV itself should be treated like an STI. Those researchers are my guests today. Linke Voestertil is a senior research fellow at Monash University's Melbourne Sexual Health Center. Katrina Bradshaw is a professor of sexual health medicine at Monash University and Alfred Hospital. Before we dive into our conversation, it's important to note that while we'll be discussing treating BV as an STI, people can be diagnosed with BV even if they've never had sex.

It's an imbalance of vaginal bacteria and one we don't really understand very well at that, so there are probably multiple ways it can come about. The point of this new research wasn't to figure out how people acquire BV, but rather to understand whether transmission between partners can make treatment more difficult. Now that that's out of the way, let's talk about Lenka and Kat's new study.

Thank you both so much for coming on to chat today. I'm really looking forward to it. So I should start by saying I'm personally a big sexual health nerd. And when I saw the news release for your study, I was like, this is a huge deal. But I recognize that not all of our listeners spend as much time thinking about this stuff as I do. So here's a basic question maybe for you, Kat. What is BV? Yeah, so bacterial vaginosis is

really has been considered a microbiome disorder or a dysbiosis. So we see a shift in that optimal vaginal microbiome. So in women, an optimal vaginal microbiome actually is characterized by these bacteria called lactobacilli that secrete lactic acid, and we have a low bacterial diversity and a really acidic pH. So it's actually the opposite of the gut.

But in BV, we see these healthy bacteria just vanish. They just disappear and they're replaced by a range of mixed bacteria that we refer to as BV bacteria. And these bacteria secrete chemicals called amines that produce this smell that

And they actually form a biofilm. So they create a little sort of scaffold that they all live in to protect themselves from host responses and antibiotics.

And so this creates also this characteristic vaginal discharge. And the problem with BV is that we still haven't found a single infectious cause that is only present in women with BV and absent in women without. So it's really what we call a polymicrobial infection. That isn't to say that there isn't a single infectious cause. We just haven't found it yet.

So really, that is what characterizes BV in the symptoms and what we see under the microscope. But it's common. It affects really one in four women globally. And so your new studies suggest that BV could be considered a sexually transmitted infection. Could you unpack what you did to determine that?

So the acquisition of BV is associated with exposure to new sexual partners in a lot of studies. It's associated with lack of condom use. And in fact, it has the incubation period that's quite typical of a bacterial STI. So looking like it's about three to four days old.

And conversely, what one sees is that when a woman is treated, her rate of treatment failure or recurrence is actually really high, astonishingly high. If you follow women for three, six months, 12 months, you see more than 50% get their baby back again. And in fact, this is even higher if a woman has a regular sexual partner, it's 60 to 80%.

So it really speaks to a woman being reinfected. Because if you had chlamydia and you are in a monogamous relationship and you do not treat that regular partner, your rate of recurrence is really high. So this profile was really evident

to me for many years as a clinician, but then evident to us when we did our studies. And every single treatment strategy we tried that is directed solely at women, which is globally what is recommended, just treat women, really failed to improve cure. And then when Lenka did all the detailed analyses of our trials,

This one factor just kept popping out each time. Regular partner was very much driving treatment failure.

So this finally got to a point where we felt we needed to do a treatment trial. So, Linka, could you tell me a little bit about the study design and how you were able to show in the first place that BV had this profile that resembled an STI? Yeah, sure. So we've conducted many studies over multiple years to acquire this body of evidence that Kat has just told you about.

So we thought it was time to revisit partner treatment. And there were partner treatment trials that had been conducted before, predominantly in the 80s and 90s.

And all of these partner treatment trials, very few of them improved cure for women. But in around 2012, there was a great review written by Supriya Mehta, and that really highlighted that the failure of these trials was likely due to the limitations of the trials and shouldn't be taken as evidence that sexual transmission isn't occurring. Mm-hmm.

And another big thing in these trials and another one since then that was well designed was that they all used an oral antibiotic in the male partners of women with BV. But since these trials are being conducted, there was a big body of molecular evidence showing, and this is where they use genetic sequencing, DNA sequencing. And what researchers, including us, have found is that the

the bacteria that are associated with BV are located in two sites on the male penis as well. So inside the urethra, which is the tube men pee through, and also on the penile skin around the outside of the penis. So

We decided that we needed to try two different antibiotics to target the two different sites of carriage of these BV organisms. So in our trial, and we ran a couple of pilot studies before we did the main trial, we used this dual therapy approach for men. And we recruited women with BV that were in monogamous relationships with a male partner.

And we use this concurrent dual therapy approach for couples and treated them for a week at the same time.

And in our pilot trials, we found that this had an effect on the BV bacteria in men and women. Then we had to conduct a randomised control trial to further strengthen the evidence that we were seeing. And this is where we randomised couples to either getting partner treatment or to the current standard practice, which is female-only treatment. We aimed to recruit 342 couples to this trial.

And we followed couples for over 12 weeks to see if the partner treatment strategy had a beneficial effect or not. But in fact, after we had 150 couples recruited, the data were viewed by an independent data safety monitoring board. And what they told us is that we could stop the trial because one of the two groups was what we call inferior or superior to the other group.

And in fact, we then analyzed the data and showed that the partner treatment group was significantly improved cure for women. Yeah. So I know that sometimes labeling something as an STI can be kind of controversial. There's so much stigma around them. I mean, back when we had our big MPOX outbreak here in the U.S.,

It was mostly spreading via sex between men. And there were a lot of think pieces about whether it would be harmful or helpful to start talking about it and labeling it as an STI. Have you faced any of that same kind of pushback? What I would say as a clinician is

And from also, our group has conducted quite a lot of qualitative studies, is that bacterial vaginosis is not an insignificant condition. It is a condition that is associated with considerable distress for women. It has very significant impacts on women's quality of life, including their relationships.

And it is associated with a very broad range of complications. It increases women's risk of catching sexually transmitted diseases, HIV, of transmitting HIV, preterm birth, miscarriage. So far, women are told that this is just an imbalance of their bacteria and they are given cycle after cycle of antibiotics.

It's resulted for many women in a lot of distress and frustration with the healthcare profession. And so I think when we talk about is it stigmatising to call bacterial vaginosis or to actually identify that sexual transmission is key to the development and recurrence of BV, my answer is simply no.

It is a balance and it is doing women an enormous disservice to withhold that information. It is doing their partners an enormous disservice to withhold that information. And so it is important to actually call out transmission of BV to be brave enough to do it. And I use the word brave because there is pushback about this.

We are not saying that for women in a situation with highly recurrent BV that sexual transmission is solely responsible for their ongoing bacterial vaginosis. We know that for some women, once they've acquired it through a transmission event, that they actually fail to clear it. And this is probably related to factors like dense biofilm and inflammation

into uterine devices, so foreign bodies that help bacteria persist. So our messaging is really that this trial has proven that sexual transmission of BV occurs.

It has confirmed what we have known for years, that it has the epidemiological profile of an STI. It has also confirmed the results from studies and meta-analyses that condoms are protective against BV, which is a very helpful, empowering message for women and their partners in terms of prevention.

But it is important to deliver that information in a sensitive way. So what we do with couples is we talk about exchanging and sharing bacteria. So we talk about exchanging good bugs and exchanging bad bugs. And we often start with analogies like sharing a glass of water or a drink bottle,

Shaking hands, kissing and having sex all results in exchange of good and bad bugs between humans. This is a dynamic process that happens all the time. And BV bacteria are some of the less optimal bacteria that can get exchanged during sex.

Men can carry these bacteria in the absence of obvious symptoms and there is no test for men. So how would a man know that they had those bacteria? So we try and pull out all the blame and talk about this being a shared responsibility to bring everyone on that journey so that we really try to remove the stigma of the

This is an STI. You gave me this. I didn't have this until you came along. It's complicated, but then all things in life are actually complicated or important things like this are complex. And I, on balance, I think it is far worse to withhold this information from women and their partners than to deliver it in a sensitive and thoughtful manner. Absolutely. Absolutely.

What else are we still looking to understand about BV? What questions remain to answer? Yeah, so Kat just alluded to this. We still don't know what the actual cause of BV is. So whether there is one kind of founder or first organism that has to be present before other organisms can come in and that becomes the polymicrobial or multi-organism infection that we see with BV.

And getting a better treatment for that persistent biofilm or dense infection is something that we also need to develop. When we find that out, we can improve the diagnostic for BV and also make the treatment more specific to the bug that we can then attribute to BV rather than using sort of what we call broad spectrum or broad antibiotics.

Another thing that we still would like to uncover, is there something that is transferred between couples that is driving that recurrent infection? So is there a specific organism that's sexually exchanged or sexually transmitted?

And also, if there is something that we can find in men that's sexually transmitted, could we develop a test for that organism or group of organisms so that then we can bring men into preventative strategies for BV? And one other thing is we've just focused this study on women who have sex with men.

But we know from, again, the body of literature and also from our past studies that women and other gender diverse individuals with a vagina can share these same BV-causing bacteria. In fact, when there's a couple where both have a vagina, there's...

their vaginal microbiome is highly concordant. So we recognise that partner treatment in this group, it is sort of integrated into clinical guidelines where if someone has a female partner, they're encouraged to go and get tested and treated. But we're also conducting studies to try and inform guidelines in this space as well.

So this isn't an exclusive treatment strategy for couples where it's a penis and a vagina. It's also a strategy that could include all monogamous couples. I think just in terms of our messaging, this is a very big change to clinical practice. So we have built a website at Melbourne Sexual Health Centre called

that provides all the information that consumers and health professionals need to actually understand, have that discussion as a couple, as a doctor and a patient, as a pharmacist dispensing. We've got animations of how to use the medication for men. We've got downloadable treatment instructions and programs

put it up for everybody to be able to access for free globally and to adapt it to their own needs, for their own populations, their own clinical services. We just want to make this as simple and accessible as possible for people so that they can access it wherever they are.

Yeah, we'll definitely link to those resources in our show notes. I think it's incredible that you've made that available. Thank you both so much for coming on to talk us through this. It's been really interesting and hopefully helpful for some of our listeners. Yes, thank you so much for having us. Thank you. We've really enjoyed that opportunity to talk with you.

That's all for today's episode. We'll be back on Friday with a fascinating story about how certain prenatal tests can inadvertently detect cancer in pregnant people. Science Quickly is produced by me, Rachel Feltman, along with Fonda Mwangi, Kelso Harper, Naima Marci, and Jeff DelVecchio. This episode was edited by Alex Sagiara. Shaina Posis and Aaron Shattuck fact-check our show. Our theme music was composed by Dominic Smith. Subscribe to Scientific American for more up-to-date and in-depth science news.

For Scientific American, this is Rachel Feltman. See you next time.