Researchers explain why bacterial vaginosis keeps coming back
A Monash University and Melbourne Sexual Health Centre study found two separate pathways behind repeat infections — re-infection and bacteria that survive the first round of treatment.
Researchers at Monash University and the Melbourne Sexual Health Centre have identified two separate reasons why bacterial vaginosis keeps coming back in some women even when their male partner is treated for the infection at the same time.
Bacterial vaginosis (BV) is the most common vaginal condition among women of reproductive age. It is caused by a loss of healthy vaginal bacteria and an overgrowth of other bacteria that upsets the natural balance of the vaginal microbiome, the researchers said.
A 2025 study by the same two institutions, published in the New England Journal of Medicine, showed that treating male partners alongside women reduces BV recurrence by more than 60%. The discovery reshaped international thinking on the condition and won the 2026 Australian Infectious Diseases Research Centre Eureka Prize for Infectious Diseases Research.
Their latest study, published in The Lancet Obstetrics, Gynaecology & Women’s Health, builds on that finding to explain why some women still get a repeat diagnosis of BV even when their partner is treated at the same time. It identifies two distinct pathways to repeat infection: re-infection, and persistence of BV-bacteria that survive the initial treatment.
Dr Lenka Vodstrcil, a senior research fellow at Monash University and the Melbourne Sexual Health Centre who led the study, said the finding has allowed the team to work on tailoring treatments to improve cure rates for millions of women worldwide.
“While partner treatment improves cure for most women in a monogamous relationship, there are some women who have persistent BV-bacteria that survive initial therapy before couples resume sex after treatment,” Vodstrcil said. “By identifying this early, we can intervene with more intensive female-focused treatments before the infection takes hold again.”
Professor Catriona Bradshaw, the study’s senior author and head of research translation and mentorship at Monash University and the Melbourne Sexual Health Centre, said the team is trialling longer courses of antibiotics and new antibiotic combinations designed to eradicate persistent BV-bacteria.
“Using partner-treatment to mitigate re-infection and more intensive strategies that target persistence of BV-bacteria, we hope to create more effective treatment approaches that can be tailored to an individual and achieve higher levels of cure for all women,” Bradshaw said.