Study highlights the interplay between vaginal microbiota and genital inflammation in response to treatment

30 September 2021

In a recent collaborative CAPRISA-led study, researchers concluded that metronidazole for the treatment of BV induced short-term shifts in the vaginal microbiota and mucosal cytokines, while treatment failures promoted persistent elevation of pro-inflammatory cytokine concentrations in the genital tract.

The study, Temporal changes in vaginal microbiota and genital tract cytokines among South African women treated for bacterial vaginosis, published recently in the journal Frontiers in Immunology, researchers investigated the effects of metronidazole treatment on the vaginal microbiota and genital cytokines among  56 symptomatic South African women with BV [defined as Nugent score (NS) ≥4] using 16S rRNA gene sequencing and multiplex bead arrays.  

Among 56 BV-positive women, researchers observed short-term BV clearance (NS <4) in a proportion of women six weeks after metronidazole treatment, with more than half of these experiencing recurrence by 12 weeks post-treatment. BV treatment temporarily reduced the relative abundance of BV-associated anaerobes and increased lactobacilli species (mainly L. iners), resulting in significantly altered mucosal immune milieu over time (Figure).

In a linear mixed model, the median concentrations of pro-inflammatory cytokines and chemokines were significantly reduced in women who cleared BV compared to pre-treatment. BV persistence and recurrence were strongly associated with mucosal cytokine profiles that may increase the risk of HIV acquisition. Concentrations of these cytokines were differentially regulated by changes in the relative abundance of BVAB1 and G. vaginalis.

“The data suggest the need to improve clinical management of BV to minimize BV related reproductive risk factors,” says lead author, Dr Andile Mtshali, at the CAPRISA Mucosal Immunology Laboratory. 

For further reading  see:
Mtshali A, et al. Temporal changes in vaginal microbiota and genital tract cytokines among South African women treated for bacterial vaginosis. Frontiers in Immunology 2021; 12:730986.

Figure: Relative abundance of the twenty most common taxa in cervicovaginal bacterial communities in women (n=56) before and aftertreatment with metronidazole with and without sexually transmitted infection (STI) treatment (A) at baseline; (B) at 6 weeks post-treatment, and (C) at 12 weeks post-treatment