Microorganismos do solo e de manguezais: fonte de produtos antimicrobianos.

Abstract

Systemic fungal infections are responsible for high morbidity and mortality especially in immune-sensitive patients. The treatment with the available antifungal substances is long and causes various collateral effects, which justifies the search for new antifungal agents. In Brazil, endemic diseases, such as Tuberculosis, Leishmaniasis and Chagas Disease, also need new drugs to increase the possibilities of their cure. The biodiversity of microorganisms found in the ecosystems provide excellent perspectives for the discovery of pharmacologically active molecules. In this study, microorganisms extracted from the soil and from the mangrove swamps of the Brazilian coast were analyzed with respect to their antifungal, antimycobacterial, leishmanicidal and trypanocidal actions. Eighty-three actinobacteria from the soil and fungi from the mangrove swamps were isolated and tested antagonistically in relation to the fungi Trichophyton rubrum, Candida albicans, Aspergillus fumigatus e Cryptococcus neoformans. Twenty-three of them inhibited the growth of the pathogens (producing circles ≥ 2mm of inhibition to growth) and were cultivated in a culture medium of Potato Dextrose for seven days. From the supernatant of the culture of the microorganisms, twenty-three organic extracts were obtained and analyzed taking in consideration their antimicrobial action through the determination of their minimum inhibitory concentrations (MICs). Five extracts presented MICs equal or less than 400 µg/mL over the pathogenic fungi and two presented significant action against the trypomastigote of Trypanosoma cruzi. For the promastigote of Leishmania amazonensis and of Mycobacterium tuberculosis H37Rv, the extracts were not effective. The five isolated producers of the extracts with promising antimicrobial action were fungi from the mangrove swamps and were taxonomically identified as to their genus. The purification of these five more effective extracts using high efficiency liquid chromatography for the separation of the active ingredient was not concluded but the chromatography data of the mass spectrometry indicate that the extracts are made of a small number of molecules. The results indicate that fungi from mangrove swamps present better microbial action than the actinobacteria tested and present promising perspectives for the research of new antimicrobial agents.