PERSISTENT vaginal bacteria may help explain why bacterial vaginosis (BV) returns in some women despite simultaneous treatment of their male partners, according to a pooled analysis of four Australian studies.1
The findings suggest that preventing reinfection addresses only part of the problem. For some women, bacteria associated with BV appear to survive initial treatment, highlighting the need to investigate approaches that also tackle persistence.
Researchers analysed 188 couples from two pilot studies, the male-partner treatment arm of the StepUp randomised controlled trial, and an open-label extension. All couples received concurrent treatment, allowing investigators to examine factors associated with a repeat diagnosis after both partners had been treated.
At 4 weeks, 39 women had repeat BV, a cumulative incidence of 20.7%. The investigators also assessed vaginal microbiota shortly after treatment using the Nugent score, a laboratory measure of bacterial composition.
Among 176 women with day 8 results, 63% had scores of 0–3, indicating no BV, while 30% had intermediate scores and 7% had scores consistent with BV.
Women with a day 8 Nugent score of 4–10 had a higher likelihood of repeat BV at 4 weeks than those with scores of 0–3. After adjustment for study group and intrauterine device use, the risk ratio was 2.82, with a 95% confidence interval of 1.57–5.07.
The researchers interpret the findings as evidence that repeat diagnoses can involve both reinfection and bacterial persistence. Their accompanying institutional report explains that persistent BV-associated bacteria can remain after antibiotics, before couples resume sex.
This distinction matters when interpreting a repeat diagnosis: it may reflect incomplete bacterial clearance rather than a new episode acquired after treatment.
The Monash University and Melbourne Sexual Health Centre team is investigating longer antibiotic courses and different antibiotic combinations to target persistent bacteria. These approaches aim to complement partner treatment and improve the prospect of lasting cure.
However, this pooled analysis did not test whether intensifying treatment in response to an early Nugent score improves outcomes. Its findings identify a potential marker of repeat BV, rather than establish a new treatment protocol.
For clinicians, the study supports further investigation of early microbiological response alongside partner treatment. Prospective trials will be needed to establish whether acting on that information can improve sustained cure without unnecessary antibiotic exposure.
References
Vodstrcil LA et al. Determinants of repeat bacterial vaginosis in concurrently treated couples: a post-hoc pooled cohort study. The Lancet Obstetrics, Gynaecology, & Women’s Health. 2026. doi:10.1016/S3050-5038(26)00259-1.
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