Adhesion of Histoplasma capsulatum to pneumocytes and biofilm formation on an abiotic surface.

The pathogenic fungus, Histoplasma capsulatum, causes the respiratory and systemic disease 'histoplasmosis'. This disease is primarily acquired via inhalation of aerosolized microconidia or hyphal fragments of H. capsulatum. Evolution of this respiratory disease depends on the ability of H. capsulatum yeasts to survive and replicate within alveolar macrophages. It is known that adhesion to host cells is the first step in colonization and biofilm formation. Some microorganisms become attached to biological and non-biological surfaces due to the formation of biofilms. Based on the importance of biofilms and their persistence on host tissues and cell surfaces, the present study was designed to investigate biofilm formation by H. capsulatum yeasts, as well as their ability to adhere to pneumocyte cells. H. capsulatum biofilm assays were performed in vitro using two different clinical strains of the fungus and biofilms were characterized using scanning electron microscopy. The biofilms were measured using a 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium-hydroxide (XTT) reduction assay. The results showed that both the H. capsulatum strains tested were very efficient at adhering to host cells and forming biofilm. Therefore, this is a possible survival strategy adopted by this fungus.

Comparative study of disk diffusion and microdilution methods for evaluation of antifungal activity of natural compounds against medical yeasts Candida spp and Cryptococcus sp / Estudo comparativo entre os métodos de difusão em disco e de microdiluição para avaliação de atividade antifúngica de produtos naturais contra as leveduras de interesse médico Candida spp e Cryptococcus sp

Antifungal activity of natural products has been tested by adapting methods designed for synthetic drugs. Inthis study, two methods for the determination of antifungal activity of natural products, agar diffusionand broth microdilution, the CLSI reference methods for synthetic drugs, are compared and discussed. Themicrodilution method was more sensitive. The minimal inhibitory concentrations (MIC) of crude extracts,fractions and pure substances from different species of the plant families Piperaceae, Rubiaceae, Clusiaceae, Fabaceae and Lauraceae, from the Biota project, were determined. Antifungal activities against Candida albicans, C.krusei, C.parapsilosis and Cryptococcus neoformans were produced by several samples

Atividade antifúngica de produtos naturais foi determinada após algumas adaptações de métodos preconizados para fármacos sintéticos. Neste estudo foram comparados e discutidos os métodos para determinação de atividade antifúngica de produtos naturais por duas metodologias, difusão em ágar e microdiluição em caldo, segundo método preconizado pelo CLSI para fármacos sintéticos. A concentração mínima inibitória foi determinada de extratos brutos, frações e de substâncias puras de diferentes espécies de plantas das famílias Piperaceae, Rubiaceae, Clusiaceae, Fabaceae and Lauraceae do projeto Biota. Vários apresentaram atividade antifúngica para as levedurasCandida albicans, C.krusei, C.parapsilosis and Cryptococcus neoformans.