<i>In vitro</i> study of essential oils encapsulated in chitosan microparticles against <i>Histoplasma capsulatum</i> and their pathogenicity in <i>Caenorhabditis elegans</i>

Histoplasmosis, caused by <i>Histoplasma capsulatum</i>, poses risks for immunocompromised individuals. With limited therapeutic options, this study explores microparticles as antimicrobial delivery systems for <i>Cymbopogon flexuosus</i> and <i>Pelargonium graveolens</i> essential oils against <i>H. capsulatum</i>. The broth microdilution assay showed MICs of 32 to 128 µg/mL in filamentous phase and 8 to 64 µg/mL in yeast phase. Combining microparticles with antifungal drugs demonstrated synergistic effects in both filamentous and yeast-like forms with amphotericin B or itraconazole. Chitosan microparticles reduced <i>H. capsulatum</i> biofilm biomass and metabolic activity by about 60% at 512 µg/mL. <i>In vivo</i> evaluation with <i>Caenorhabditis elegans</i> showed <i>H. capsulatum</i> caused over 90% mortality. These findings highlight the potential use of chitosan microparticles as a delivery system for essential oils against <i>H. capsulatum</i>, especially in combination with other compounds.