Efeito antifúngico do geraniol sobre células planctônicas e biofilmes do complexo de espécies Candida parapsilosis

Abstract

Candida parapsilosis species complex represents an emerging threat to the nosocomial environment due to their ability to produce biofilms adherent to medical devices. Faced with a global rise in strains resistant to common antifungal treatments, geraniol, a terpene isolated from different essential oils, presented itself as a promising therapeutic alternative due to its antimicrobial activity and antifungal potential. Based on this evidence, this study evaluated the in vitro effects of geraniol against species of the C. parapsilosis complex, in planktonic and biofilm forms, and its interaction with other antifungals. 18 isolates were subjected to broth microdilution assay, using geraniol (4 - 1024 μg ml-1

), fluconazole (0.125 - 64 μg ml-1 ),

itraconazole (0.0313 - 16 μg ml-1

), amphotericin b (0.0313 - 16 μg ml-1

) and caspofungin

(0.01625 - 8 μg ml-1

) to determine the minimum inhibitory concentration (MIC). In addition, a cell count was performed to determine the minimum fungicide concentration. The drugs were tested in mature biofilms, using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium (MTT) reduction assay to determine metabolic activity and the biomass quantification by crystal violet staining assay. The interaction test between geraniol and antifungals was carried out using the checkerboard method, using the compounds: geraniol with amphotericin b, fluconazole and caspofungin. The MIC for geraniol was between the ranges 256-512 μg ml-1, while for antifungal drugs they were: amphotericin b <0.031 - 1 μg ml-1, fluconazole 0.25 – 4 μg ml-1, itraconazole <0.031 - 0 .25 μg ml-1 and caspofungin 0.125 – 1 μg ml-1. 2 strains of Candida metapsilosis were dose-dependently sensitive (MIC50 4 μg ml-1) to fluconazole and 1 strain of Candida orthopsilosis was dose-dependently sensitive to fluconazole and itraconazole (respectively MIC50, 4 μg ml-1 and 0.25 μg ml -1 - 1), while 7 strains had reduced sensitivity to amphotericin b (MIC 1 μg ml-1). Geraniol showed antibiofilm activity, with an average reduction in metabolic activity of 38.33% (±20.90%) and 30.69% (±17.37%) in the total biomass of mature biofilms, at MIC concentrations (p < 0.05). C. orthopsilosis biofilms proved to be more resistant to reduced metabolic activity at the MIC concentration, compared to other strains in the complex. Geraniol showed synergism with amphotericin b and caspofungin. The results obtained demonstrate the effectiveness of geraniol's antifungal activity against strains of the Candida parapsilosis complex, in its planktonic form and mature biofilms, in addition to a potential combination with amphotericin b and caspofungin to be explored.