Efeito do farnesol sobre o fenótipo de resistência e a produção de fosfolipase e protease em cepas de Candida spp

• Autor(a) principal: Teixeira, Carlos Eduardo Cordeiro
• Data de Publicação: 2011
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Ceará (UFC)
• Texto Completo: http://www.repositorio.ufc.br/handle/riufc/4789
• topic: Cândida; Fenótipo; Combinação de Medicamentos; Antifúngicos

There are several reports of in vitro resistance to antifungal drugs, especially azole derivatives, in strains of Candida spp. For this reason, the pursuit for new compounds that present antifungal properties is necessary. Thus, this study aimed at evaluating the antifungal activity of farnesol and its interaction with classical antifungal drugs against Candida spp., as well as evaluating its effect on the production of phospholipase and protease, which are important virulence factors for Candida species. Fourty-five strains of Candida spp. (23 C. albicans, 16 C. parapsilosis and 6 C. tropicalis) were tested through broth microdilution as described by the Clinical Laboratory Standards Institute (CLSI), document M27A2, and the minimum inhibitory concentrations (MICs) for amphotericin B (AMB), fluconazole (FLC), itraconazole (ITC), caspofungin (CAS) and farnesol (FAR) were individually determined. In addition, the effect of FAR on phospholipase activity was assessed by growing the strains on 2% Sabouraud agar, supplemented with egg yolk, and protease activity was determined through spectrophotometry. Then, 13 strains were randomly chosen, pre-incubated at three sub-inhibitory concentrations of FAR for 24 hours and re-submitted to microdilution assay. For the 45 evaluated Candida spp. strains the MIC values for FAR varied from 9.37 to 150 µM. For the classical antifungal drugs, MICs ranged from 0.0625 to 4 µg/mL for AMB, with 19 resistant strains (MIC>1 µg/mL); from 0.0125 to >64 for FLC, with 18 resistant strains (MIC> 64 µg/mL); from 0.03125 to >16 µg/mL for ITC, with 35 resistant strains (MIC ≥1 µg/mL), and from 0.0625 to 2 µg/mL for CAS, with six resistant strains (MIC≥2 µg/mL). All resistant strains were tested against the combination of FAR with the drug to which they presented resistance. The combination of AMB and FAR was synergistic against 94.7% (18/19) of the Candida spp. isolates, as shown through the obtention of FICI≤0.5. FAR and FLC interacted synergistically against all tested strains (n=18), exhibiting FICI values of ≤0.5. The combination of FAR and ITC presented synergistic interactions (FICI≤0.5) against 94.4% of the tested isolates (33/35). Finally, FAR and CAS showed to interact synergistically (FICI≤0.5) against all tested strains. Concerning virulence factors, it was observed that 17/45 isolates produced phospholipase, with a mean Pz of 0.71. After incubating these strains at three different concentrations of FAR the mean Pz values of 0.71, 0.61 and 0.54 were obtained, after incubation at the lowest, the intermediate and the highest concentrations of FAR, respectively. In addition, it was observed that the 14 randomly chosen strains that were screened for protease activity produced low concentrations of these enzymes, varying from 0.002 to 0.02 U/mL and that FAR presented no effect on enzymatic production. Finally, it was observed that pre-incubating strains at the highest sub-inhibitory concentration of FAR reduced the MIC range of the tested antifungal drugs. These results especially show the effects of FAR on the susceptibility of Candida species to classical antifungal drugs, providing perspectives for the development of researches on the mechanisms of this compound on fungal cell metabolism