Atividade antifúngica do fluconazol em modelo experimental In vivo de Galleria mellonella: um estudo para padronização

Abstract

The incidence of fungal infections and the growing resistance to antifungals are current challenges in the health area and justify the performance of studies that prospect new therapies or adjuvant therapies. Systemic candidiasis occurs, especially, in a hospital environment, contributing to high mortality rates, between 58 to 81% of cases of nosocomial infections. The invertebrate Galleria mellonella has received increasing attention as an alternative model to the use of animals, but there is a high variability of parameters found in studies of infection by Candida species in this experimental model. This study aimed to standardize an experimental model for prospecting new anticandida drugs through the alternative animal model of G. mellonella larvae. An experimental study was carried out in vivo, with direct observation in the laboratory. Cultures of C. albicans strains, two standardized (ATCC 90028 and ATCC10231) and two isolated from the oral cavity (A1 and A2) were standardized in different inoculum densities to determine the levels of infection (non-lethal infection; lethal infection and super infection). Fluconazole toxicity tests were performed at different dosages. The infected larvae were submitted to different models of fluconazole treatment (different antifungal dosages and administration times). The data obtained from the viability analysis were plotted on Kaplan–Meier survival curves and analyzed by the log-rank test in GraphPad Prism 5.0 (p < 0.05). Fungal inocula at 2x104, 2x105 and 2x106 cél/mL density were determined as non-lethal infections; at 2x107 cél/mL density, only the clinical isolate A2 was able to cause lethal infection; the 2x108 cél/mL density was determined to cause super infection. Fluconazole showed low toxicity to G. mellonella larvae. Among the treatment models tested, therapies with a single dose of 20mg/kg and 80mg/kg of fluconazole were the ones that provided the best survival rate of G. mellonella larvae with lethal infection and super infection by C. albicans, respectively. The methodological parameters used in this study regarding the levels of infection, toxicity of the systemic antifungal fluconazole, as well as the treatment models with different doses of fluconazole, can be used as parameters in studies for the prospection of anticandida drugs in the experimental model G. mellonella.