Antifungal Activity of Essential Oils Against <i>Candida</i> Species Isolated from Clinical Samples

Abstract

We evaluated the in vitro antifungal activity of essential oils obtained from the aromatic plants <i>Laurus nobilis</i>, <i>Thymus vulgaris</i>, <i>Mentha piperita</i>, <i>Cymbopogon citratus</i> and <i>Lippia junelliana</i> against the following <i>Candida</i> species isolated from clinical samples: <i>C. krusei</i> (n = 10); <i>C. albicans</i> (n = 50); <i>C. glabrata</i> (n = 70) and <i>C. parapsilosis</i> (n = 80). The minimal inhibitory concentration (MIC) was determined according to EDef 7.3.1 document from EUCAST. Amphotericin B and fluconazole were the antifungal drugs used as inhibition control. The concentration ranges evaluated were 0.4–800 and 0.03–128 mg l⁻¹ for essential oils and antifungal drugs, respectively. MIC₅₀ and MIC₉₀, mode and ranges were calculated. All the <i>Candida</i> spp. evaluated were susceptible to amphotericin B (MIC ≤ 1 mg l⁻¹), while fluconazole was inactive for <i>C. krusei</i> (MIC ≥ 32 mg l⁻¹) and intermediate for <i>C. glabrata</i> (MIC ≤ 32 mg l⁻¹). The essential oils showed antifungal activity on <i>Candida</i> spp. tested with MIC₉₀ values ranging from 0.8 to 800 mg l⁻¹. In general, the most active essential oils were <i>L. nobilis</i> and <i>T. vulgaris</i> (MIC₉₀ 0.8–0.16 mg l⁻¹), and the least active was <i>C. officinalis</i> (MIC₉₀ 400–800 mg l⁻¹). <i>C. krusei</i> was inhibited by 5/6 of the essential oils evaluated, and <i>C. glabrata</i> was the least susceptible one. This in vitro study confirms the antifungal activity of these six essential oils assayed which could be a potential source of new molecules useful to control fungal infections caused by some <i>Candida</i> species, including those resistant to antifungal drugs.