Study Reveals Sexual Transmission of Bacterial Vaginosis

Key questions remain after the publication of a landmark study in The New England Journal of Medicine that found bacterial vaginosis (BV), which affects nearly a third of

women worldwide, can be transmitted sexually.

The study findings could shift the treatment focus to both men and women instead of women only.

But experts contacted by Medscape Medical News added information about how BV develops and call for further research on the condition that can cause infertility, premature births, and newborn deaths.

Findings of the Study

The study, published on March 5, was led by Lenka A. Vodstrcil, PhD, with the Melbourne Sexual Health Centre, School of Translational Medicine, at Monash University in Carlton Australia, and colleagues.

Vodstrcil’s team found that in the trial of 164 couples in which each woman had BV and was in a monogamous relationship with a male partner, treating BV as a sexually transmitted infection (STI), with both sexual partners treated simultaneously, led to significantly higher cure rates than the current practice of treating only women.

“This successful intervention is relatively cheap and short and has the potential for the first time to not only improve BV cure for women but opens up exciting new opportunities for BV prevention,” coauthor Catriona S. Bradshaw, PhD, also with the Melbourne Sexual Health Centre at Monash University, said in a press release.

In the randomized, open-label, controlled trial, the women received first-line recommended antimicrobial agents and the male partners received oral and topical antimicrobial treatment (400 mg metronidazole tablets and 2% clindamycin cream applied to penile skin, both twice daily for 7 days) in the partner-treatment group.

In the control group, women received first-line treatment and the male partners were not treated. The primary outcome was the recurrence of BV within 12 weeks. Historically, more than half of women with BV experience a recurrence within 3 months after taking a weeklong course of oral antibiotics, the researchers noted.

In the modified intention-to-treat population, BV recurred in 35% of women in the partner-treatment group and in 63% of women in the control group, which corresponded to an absolute risk difference of −2.6 recurrences per person-year (95% CI, −4.0 to −1.2; P < .001). The trial was stopped early “because treatment of the woman only was inferior to treatment of both the woman and her male partner,” the authors wrote.

Other Factors May Affect BV Development

Some experts, however, point to unanswered questions that beg further research.

Mykhaylo Usyk, PhD, MPH, MSci, a research assistant professor in the Departments of Microbiology and Immunology, Department of Pediatrics at the Albert Einstein College of Medicine in the Bronx, New York, said while he thinks BV “absolutely can be transmitted sexually, more research needs to be done to see exactly which types are transmissible,” especially because the trial was not completed for ethical reasons. The sample size was modest, and recurrence was not stopped for all who underwent the intervention.

“I don’t know that I would say BV itself is an STI,” said Usyk, who published a study on the effect of BV on recurrence of chlamydia infection. “BV is also an indicator like a fever. It’s a symptom of some other disease.”

It’s clear, he said, that men are acting as a reservoir. “There are some underlying bugs which the men are harboring, and unless you treat them the BV is going to come back.” 

Usyk said before giving men and women antibiotics routinely to treat and prevent BV, he would like to see more research on which subtype of BV is transmissible.

Smoking, Douching May Contribute 

Rebecca Brotman, PhD, MPH, who studies the human vaginal microbiome and BV at the Center for Advanced Microbiome Research and Innovation at the University of Maryland School of Medicine, Baltimore said, “Other contributing factors, such as smoking or intravaginal practices like douching and using lubricants may also disrupt the vaginal microbiome and contribute to the development of BV.” 

She said the trial provides compelling evidence supporting the longstanding hypothesis that BV-associated bacteria can be sexually transmitted, and she agreed these trial results will transform how clinicians treat and deliver care for BV. “Prior to the trial’s publication, evidence was limited that men could transmit BV,” she noted.

However, she said, “While the trial represents a significant achievement for BV treatment, further work is needed to validate the findings in other populations. For example, 80% of the men in the trial were uncircumcised, and one third of the women were using intrauterine devices, both of which can affect the presence of BV-associated bacteria.”

She points to a wealth of evidence supporting sexual transmission of BV in research: Frequent co-occurrence of BV with STIs; a higher prevalence among women with multiple or new sexual partners; an increased incidence among women whose male partners have multiple recent partners; and high concordance in lesbian couples.

“Condom use also appears to help lower BV risk,” she said, “with studies indicating a reduced risk in women who abstain from sex or consistently use condoms, whereas unprotected sex is linked to higher treatment failure rates.”

‘A Huge Win for Women’

Caroline M. Mitchell, MD, MPH, director of the Vulvovaginal Disorders Program at Massachusetts General Hospital in Boston, told Medscape Medical News it’s important to remember that BV is a syndrome — “and so it may be different bacteria present person to person or episode to episode.”

“Clinically, I definitely see patients for whom BV seems very sexually facilitated — occurs only with one partner, resolves when they are not with that person. However, for others, this is not at all the case. So I don’t think this is universal. I definitely see patients who have tried abstinence and still have recurrence. I don’t think that getting BV means that one’s partner is being unfaithful in the way I would for chlamydia. However, BV does seem to be sexually facilitated, and the results of this study suggest that microbes on the penis likely play a role in at least some cases.”

She added, “For people with highly recurrent BV, I do think that there may be some passing back and forth of BV-associated bacteria between sexual partners, and that treating both people — as [recommended] in this paper — will be necessary to clear those organisms.”

She said the study offers an important move forward for helping prevent recurrence of BV in some patients. “Since treatment options in the field haven’t substantively changed since 1982, this is a huge win for women,” she said.

Findings Should Change Counseling

In an accompanying editorial, Christina A. Muzny, MD, MSPH,with the Division of Infectious Diseases at The University of Alabama at Birmingham, and Jack D. Sobel, MD,with the Division of Infectious Diseases, Wayne State University in Detroit wrote that the findings should change counseling of women.

The findings also signify the need for a major change to the treatment approach for women with bacterial vaginosis “with respect to how women should be counseled regarding the origin of their infection and to the need to engage their male partners in sharing responsibility for transmission and treatment,” the editorialists wrote. “To date, there have been no effective strategies to prevent sexual transmission of bacterial vaginosis–associated bacteria, apart from consistent use of condoms.”

This study was funded by the National Health and Medical Research Council of Australia and StepUp Australian New Zealand Clinical Trials Registry. Full author and editorialists’ disclosures are available with the full text of the papers. Usyk declared no relevant financial relationships. Brotman declared no relevant financial relationships. Mitchell is on the scientific advisory boards for Concerto Bio and Ancilia Bio and received stock options for this. She received royalties from Up to Date.

Marcia Frellick is an independent healthcare journalist based in Chicago.