Anais do Congresso Paranaense de Microbiologia
IV Congress of Microbiology in Paraná

Introduction: Chromoblastomycosis (CBM) is a subcutaneous infection caused by a group of black fungi such as Fonsecaea pedrosoi. Its characteristics range from the initial injury to extensive polymorphic lesions with chronic inflammation. Brazil is the second country with more cases in the world. The majority of patients are adult farmers, often of low income, and do not use protective equipments. Amphotericin B (AmB) is the gold standard medication for systemic mycosis, but its use in the treatment of CBM has been discouraged due to its several adverse effects and limited effectiveness against these pathogens. Therefore, it has been proposed its use in combination with other substances. Pilocarpine (PILO) is a compound extracted from Pilocarpus microphylus which has in its structure an imidazole ring similar to imidazole antifungals. This raises the hypothesis that PILO has antifungal activity. The present study aims to investigate the activity of PILO alone and in association with AmB, against CBM agents through in vitro assays. Materials and Methods: The fungal samples used in the experiments belong to the collection of the Group of Advanced Studies on Medical Mycology (GEAMICOL) and included representatives of the genera Fonsecaea, Cladophialophora, Phialophora, Rhinocladiella and Exophiala. Susceptibility tests were performed in triplicate following the broth dilution method proposed by the M38-A2 document of the Clinical and Laboratory Standards Institute. The assessment of the combinations was done according to the checkerboard technique described by Cuenca-Estrella (2004) to calculate the Fractional Inhibitory Concentration Index (FICI). Results: PILO alone was not able to inhibit any of the strains at the concentrations tested. AmB was able to inhibit the growth of all tested fungi in a range of concentrations between 1 and 8 μg/ml. The association between the two compounds demonstrated synergism to 5 strains (FICI = 0.3 - 0.5) and was indifferent to 9 (FICI = 1 - 4). This synergism may result from one substance increasing the bioavailability of the other. Conclusions: The results show that PILO does not present antifungal activity against the tested CBM agents at the concentrations assessed. The AmB activity tests in combination with PILO showed interesting results, as there was synergy mainly in the genera Cladophialophora, Phialophora and Rhinocladiella, but also in some samples of Fonsecaea pedrosoi. This ability to enhance the medicine’s action can be of great value in prolonged CBM treatments.