Bioprospecção de antimicrobianos produzidos por fungos do solo amazônico com ação frente as principais bactérias multiresistentes

Abstract

In recent years, the increase in the number of bacteria resistant to multiple drugs has become a worldwide problem, increasing the need to discover and develop new antimicrobials. Among the major bacteria characterized as multiresistant, we can highlight Staphylococcus aureus that is resistant to methicillin-oxacillin (MRSA), Enterococcus spp. vancomycin resistant (VRE), extended spectrum β-lactamase Enterobacteriaceae (ESβL) and carbapemic resistant (ERC), Pseudomonas aeruginosa and Acinetobacter baumannii multi-drug resistant (MDR). In view of this context, ten fungal lineages belonging to the collection of medical interest of the Institute of Amazonian Research (INPA) were used in the present study to carry out the bioprospection of antimicrobials produced by fungi of Amazonian soil, considering the great biotechnological potential of such microorganisms. In order to investigate the antimicrobial activity, bioprocesses were carried out to produce the fungal culture filtrate and the agar diffusion method was performed. The determination of Minimal Inhibitory Concentration (MIC), thin layer chromatography, bioautography and retention factor (Rf) were performed for the filtrate culture of the fungi that showed antimicrobial activity. For the chemical characterization of the fraction with the highest antimicrobial activity, chromatographic fractionation techniques (comparative thin-layer chromatography, liquid-liquid extraction and open-column chromatography), nuclear magnetic resonance (NMR) and mass spectrometry (MS) were used. The culture filtrate of Aspergillus (H63) and Paecilomyces (H59) showed antimicrobial activity by the agar diffusion method, well variant. The Aspergillus (H63) filtrate concentrate had a MIC of 1600 μg / mL for S. aureus (MRSA) and S. aureus (wild). Paecilomyces (H59) had MIC of 800 μg / mL for S. aureus (MRSA), S. aureus (wild), Klebsiella pneumoniae (ESβL), K. pneumoniae (KPC) and Escherichia coli (wild); and 400 μg / mL for A. baumannii (OXA-23). The ethyl acetate / methanol (1: 1 - v / v) elution system revealed the presence of three zones at UV 365 nm and bioautography determined an area with antimicrobial activity. The ethyl acetate phase presented antimicrobial activity by agar diffusion method against S. aureus (MRSA). The dichloromethane-ethyl acetate system (1: 9) obtained the best selections, which were separated according to the similarity, generating the fractions 3-4, 5-7 and 8. The fraction 5-7, presented antimicrobial activity by the agar diffusion method against S. aureus (MRSA) and A. baumannii (OXA-23). Finally, NMR and MS revealed a substance with antimicrobial activity, requiring further studies to elucidate its chemical structure and evaluation of its antimicrobial activity isolated from the other fractions. Our results indicate that the bioprospection of substances with antimicrobial activity produced by Paecilomyces (H59) is an alternative for the research of new antimicrobials against MDR bacteria.