The Antimicrobial and Toxicity Analysis of Essential Oils Used for Vaginal Infections

Abstract

The increasing resistance of bacterial and fungal pathogens to conventional treatments for vaginal infections, alongside the disruption of protective Lactobacilli by many antimicrobials, highlights the urgent need for alternative strategies. Essential oils, long used in traditional medicine and increasingly marketed in over-the-counter formulations, have been cited for their antimicrobial activity and potential microbiota-sparing properties. This study evaluated the antimicrobial efficacy, toxicity, microbiota impact, and biofilm inhibition of essential oils, both individually and in combination. Forty-six essential oils were investigated. These were assessed in terms of antimicrobial activity using broth microdilution, toxicity with the brine shrimp lethality assay, the impact on microbiota determined through Lactobacillus broth microdilution assays, and biofilm inhibition. A total of 602 combinations were tested for synergistic interactions. Citrus aurantifolia and Origanum vulgare showed broad-spectrum antimicrobial activity with non-toxic profiles and minimal inhibition of Lactobacilli. Of the 602 combinations, 101 demonstrated bacterial synergy and 48 yeast synergy; 69% were non-toxic, but only 6% spared Lactobacilli. The most promising combinations were Cinnamomum camphora with Melaleuca cajuputi, C. camphora with Ocimum sanctum, and Salvia officinalis with O. sanctum. Notably, C. camphora with M. cajuputi inhibited Candida albicans and Candida glabrata biofilms by 82% and 72%, respectively, outperforming the individual oils. These findings suggest that selected essential oils and combinations demonstrate promising in vitro antimicrobial, microbiota-sparing, and antibiofilm properties. Further preclinical evaluation is warranted to explore their role in developing microbiota- preserving therapies for vaginal infections.