Vaginal formulations selectively target Lactobacillus iners and Candida spp. while preserving Lactobacillus crispatus

Vaginal eubiosis is associated with low bacterial diversity and Lactobacillus crispatus dominance, whereas Lactobacillus iners often persists after antibiotics. We evaluated complementary approaches to inhibit L. iners and Candida spp. while preserving L. crispatus. Carbohydrate screening of five strains per Lactobacillus species showed insufficient selectivity. Oleic acid showed the widest susceptibility differential: minimum inhibitory and bactericidal concentrations were 0.4/0.8 mM for L. iners versus 1.6 to > 6.4 mM for L. crispatus. After 24 h, a mixture of 0.25% oligomeric proanthocyanidins, 0.05% ethylenediaminetetraacetic acid and 6.4 mM oleic acid yielded counts 4.8 log₁₀ CFU/mL lower for L. iners and 1.4–2.5 log₁₀ CFU/mL lower for four Candida species than controls, while preserving three L. crispatus strains. HeLa cell cytotoxicity increased at 25–100% of the undiluted mixture. Purified monacolin KA showed broader antifungal activity than monacolin K, with a 4.3-log₁₀ reduction in C. albicans counts versus vehicle controls at 50 µg/mL while maintaining high L. crispatus viability. In one patient receiving concomitant M247 supplementation and other treatments, an oil-based prototype was temporally associated with recovery of L. crispatus dominance (96.9%; community state type I). These findings support development of selective vaginal formulations; clinical efficacy and effective, cytocompatible exposures remain to be established.