Isolation And Characterization Of Compounds From Wood Decay Fungi (Wdf) With Activity Against Gram- Positive Bacteria

Abstract

For decades, fungi have been a source of anti-infective substances, especially after the discovery of penicillin. However, in recent years, the efforts of pharmaceutical companies have dwindled due to the redundancy in the discovery of anti-infective compounds. Antibiotic resistance is also on the increase worldwide, and this poses a serious clinical threat. This study explored metabolites from indigenous Ghanaian Wood Decay Fungi (WDF) by screening a library of 180 WDF. Extracts obtained from these fungi were tested against Gram-positive organisms, Methicillin- sensitive Staphylococcus aureus (MSSA) and Methicillin-Resistant Staphylococcus aureus (MRSA). Out of 180 WDF screened, 48% had antibacterial activity against both susceptible and resistant strains of S. aureus, with 23.45% showing selective activity against only the resistant strains of S. aureus. Techniques to optimize the fermentation of WDF were explored by varying the closing mechanism of fermentation vessels using filter paper capping, foam capping, loose capping and tight capping. Filter paper-covered vessels were the most suitable for the production of extracts with consistent activity. Six different media were tested for maximum production of bioactive compounds. Yeast, Peptone, Malt extract, and Dextrose (YPMD) broth aided the production of consistent antibacterial activity among the six media tested. Inhibitors of histone deacetylases (iHDACs) were used to modify broth in which two fungi were cultured. iHDACs increased the antibacterial activity of the two fungal extracts. Using a phenotypic array assay that employed synergy between standard antibiotics and phenotype modulating compounds, fungal isolates taken through activity-guided fractionation revealed five potential compounds with antibacterial activity. This study is a proof of concept that Wood Decay Fungi (WDF) have the potential of producing secondary metabolites with anti-Gram positive activity. The study also established an assay that provides a predictive power of WDF with potential novel antibacterial compounds, as well as techniques for optimizing fermentation of WDF to produce ant ibacterial compounds.