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A dose of healthy bacteria could give women the upper hand in ridding themselves of a common but annoying vaginal infection, a new clinical trial reports.

Women treated with Lactin-V – an experimental vaginal suppository containing live bacteria – were much more likely to end their recurring bouts of bacterial vaginosis than women treated with a placebo, the researchers said.

“What we’re doing essentially is knocking down the bad bacteria and then replacing the good bacteria, allowing them to grow and keep at bay the bad bacteria as part of an optimal balance,” explained lead researcher Dr Craig Cohen, a professor of obstetrics, gynaecology and reproductive sciences at the University of California, San Francisco.

Bacterial vaginosis (BV) is the most common vaginal condition in women aged 15 to 44, affecting nearly 30% of women of reproductive age in the United States, researchers said in background notes.

Antibiotic therapy

Every vagina is colonised with different strains of bacteria, Cohen said. Vaginosis occurs when “bad” bacteria overwhelm the normal “good” bacteria.

Symptoms include a thin white or grey vaginal discharge, itching or burning of the vagina, and a strong fishlike odour, according to the US Centers for Disease Control and Prevention.

The condition also increases the risk of premature birth or low birth weight among newborns, as well as upping a woman’s risk of contracting HIV and other sexually transmitted diseases, the CDC says.

Standard therapy is to treat the infection with a six-month course of a topical antibiotic gel called metronidazole, said Dr Taraneh Shirazian, director of global women’s health at New York University’s School of Global Public Health.

As Cohen and his team see it, there’s a problem with that standard therapy. Once the antibiotic therapy is done, there’s nothing to prevent the bad bacteria from overwhelming the vaginal microbiome again.

Because of that, as many as 75% of women have their infection recur within three months of treatment, researchers said.

“They’re doing what their provider recommends, they’re taking antibiotics, and even though they’re doing that, it’s coming back,” Cohen said.

Recurrent infections

In the study, 228 women who were diagnosed with bacterial vaginosis were treated with a five-day course of metronidazole gel. Two-thirds of those women were then assigned to receive Lactin-V for 11 weeks.

Lactin-V is a powder that women self-administer with a vaginal applicator. It contains Lactobacillus crispatus, a strain of bacteria that naturally occurs in the vagina. This bacteria produces lactic acid, which inhibits the growth of bad bacteria.

By the end of the initial three months, 30% of women in the Lactin-V group had experienced recurrence of their infection, compared with 45% of women in the placebo group, results showed.

“Essentially, it’s associated with a 34% reduced risk of recurrence during that 12-week time period,” Cohen said.

The women were tracked out for six months total, and those who received Lactin-V continued to do better, Cohen said.

“We also found approximately 80% of women who were in the Lactin-V arm were successfully colonized with Lactobacillus crispatus, the actual strain we tested,” Cohen said.

The findings were published on 14 May in the New England Journal of Medicine.

Shorter therapy

Shirazian said this new treatment looks promising, given that it took three months as opposed to the standard treatment of six months. Currently, women apply antibiotic gel for seven days, then twice weekly for six months to treat recurring bacterial vaginosis.

“That’s a lot shorter, which is advantageous,” said Shirazian, who wasn’t part of the study. “It’s hard to continue a therapy for six months. It’s hard to maintain it.”

However, Shirazian said future trials of Lactin-V would produce stronger results if they compare the new treatment against the current standard therapy as well as placebo.

Researchers are discussing proceeding to stage three clinical trials with the maker of Lactin-V, California-based Osel, Inc., Cohen said. There’s currently no timeline for getting the new treatment to market.

“I know there are a lot of women suffering from BV, and this product is not available now. It’s a long timeline to go through the drug approval process with the [US Food and Drug Administration],” Cohen said.

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