Estudo da atividade antifúngica do óleo essencial de Cymbopogon winterianus Jowitt ex Bor, citronelal e geraniol sobre o gênero Candida de origem hospitalar

Abstract

Candidemia is a concern in the pediatric clinic and the search for new antifungal drugs presents itself as an important strategy to improve the therapeutic arsenal against this infection. The essential oil of Cymbopogon winterianus (OECw), as well as its major citronellal and geraniol phytochemicals have pharmacological properties, including antimicrobian activity. Thus, the objectives of this study were identify and establish the frequency of Candida species isolated from candidemia of patients admitted to a pediatric public hospital in Joao Pessoa, Brazil; analyze the antifungal susceptibility of the strains and to study the antifungal activity of OECw, citronellal and geraniol against these microorganisms. Identification was performed using the CHROMagar and VITEK®2 systems. The antifungal susceptibility test was determined using the VITEK®2 automated system; minimum inhibitory concentration (MIC) and minimum fungicidal concentration (CFM) were determined by the microdilution technique; the possible mechanism of action of the products on the wall (0.8 M sorbitol) and fungal cell membrane (binding of the products to ergosterol). The isolation frequency of Candida albicans was 60% and 40% of non-albicans, with 13% for C. tropicalis, C. parapsilosis and C. pelliculosa. All isolates were sensitive to fluconazole, voriconazole, amphotericin B, flucytosine, micafugin and caspofugin, with MICs ranging from 1-4, 0.12-2, 0.5-1, 1-1.0, 0.06-0.5 and 0.25-1 μg/mL, respectively. Only one C. albicans strain was intermediate to fluconazole and voriconazole (MIC 4 μg/mL). For C. albicans strains, the MIC50 value of OECw, citronellal and geraniol was, respectively, 64, 64 and 32 µg/mL. The CFM90 value of OECw, citronellal and geraniol was, in the sequence, 256, 128 and 64 µg/mL. For Candida non-albicans isolates, the MIC50 value of OECw, citronellal and geraniol was therefore 128, 128 and µg/mL. The MFC50 value of OECw, citronellal and geraniol was, respectively, 128, 128 and 64 µg/mL. Involvement with the cell wall and binding to ergosterol were excluded as possible mechanisms of the products. Therefore, it is concluded that Candida albicans was the predominant species and that the strains were not resistant to the main antifungal agents. This study is the first to present epidemiological data on candidemia in the pediatric population in João Pessoa, Paraíba, Brazil. In addition, the essential oil of Cymbopogon winterianus, citronellal and geraniol showed antifungal activity in vitro against Candida spp. isolates, and consequently can be considered as potential antifungal products.