Atividade antibacteriana de recursos naturais contra Staphylococcus aureus

Abstract

The most common resistant bacterium in the clinical area is Staphylococcus aureus, which although present naturally in the population, has become resistant to multiple drugs. The search for antibacterial molecules from natural products is fundamental economic and social importance, as it has great potential to obtain new antibiotics. Therefore, the objective of this work was to evaluate the antibacterial activity of Trichoderma spp. against S. aureus. Initially the fungi were evaluated by the gelose block method, combining the antibacterial-producing fungi according to the similarity of their results. In this way, a fungus of each group was selected, which were cultivated in different conditions of culture medium, pH and luminosity. After cultivation and filtration, these had their antibacterial activity evaluated and the six most promising filtrates were selected for the determination of their minimum inhibitory (MIC) and bactericidal (MBC) concentrations. Thin layer chromatography, bioautography and cytotoxicity testing were then performed. For the stage of liquid culture of Trichoderma spp., It was initially chosen to elaborate a culture medium using food residues, among them the banana peel. However, during the tests, it was found that the infusion of these peels had anti-Staphylococcus activity, so the second chapter of this work aimed to evaluate the antibacterial activity of peels and pulps of three banana varieties, ripe and unripe, against strains of S. aureus, select the most promising variety and test different forms of extraction to define the most effective method. The three best banana infusion samples were selected for MIC and MBC determination. Of the 98 fungi tested by the gelose block method, 58 inhibited one or more S. aureus strains. Thereafter, four cultures of Trichoderma spp. were grown under different conditions. It was observed that the culture conditions influenced the synthesis of the antibacterial compounds of the four lines. In addition there was not a single condition that could be considered the ideal for all the fungi. The MIC of the filtrates ranged from 0.16 to 7.5 mg/mL and MBC ranged from 0.31 to 7.5 mg/mL. When subjected to thin layer chromatography, the filtrates obtained from the same fungus presented similar chromatographic profiles, but it was not possible to compare the results obtained in the bioautography. In the cytotoxicity test, no toxicity was observed for VERO cells at the concentrations tested. In relation to banana, the three varieties inhibited the growth of the pathogens, and the bark of the silver banana inhibited a greater number of S. aureus, so it was submitted to different forms of extraction. The most efficient infusion samples were submitted to the MIC test, obtaining a minimum value of 0.62 mg/mL and a maximum of 5.0 mg/mL. CBM ranged from 0.62 to >5.0 mg/mL. In view of the presented results, it was evidenced that filtered of Trichoderma spp. and banana infusions are efficient in the inhibition of growth of S. aureus, being the banana peel Silver most suitable for the extraction of these compounds in comparison to fungi.