Anti-MRSA activity of ethyl acetate crude extract from endophytic fungus Ceratobasidium ramicola IBRLCM127 isolated from rhizome of Curcuma mangga Valeton & Zijp

Abstract

The study was conducted to investigate the effects of ethyl acetate crude extract of C. ramicola IBRLCM127, an endophytic fungus which was previously isolated from rhizome of C. mangga against a common human bacterial pathogen, methicillin-resistant Staphylococcus aureus (MRSA) in order to develop a new MRSA treatmet. The efficiency of antimicrobial compounds in inhibiting or killing the bacterial cells was evaluated by adopting minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC). The effect of ethyl acetate crude extract on the growth profile of MRSA was examined using timekill assay. Scanning electron microscope (SEM) observation was opted to investigate the ultrastructural effect of MRSA cells. The results revealed that fungal extract demonstrated a bactericidal effect on MRSA with the ratio of MBC/MIC was 1. Both MIC and MBC values of the extract were 0.5 mg/mL. The result obtained from the time-kill study disclosed that the bactericidal activity of fungal extract under investigation was both time and concentration dependent. After 12 hours of exposure to the extract, the formation of cavities and a few cell debris can be observed on the bacterial cells, indicating the failure of cell wall and cell membrane to maintain their rigid structure due to the rupture caused by the extract. Prolonged exposure to the extract for up to 48 hours caused the bacterial cell wall to lyse and release its cytoplasmic content into the surrounding which led to cell death. Based on the SEM observation, the fungal ethyl acetate extract of C. ramicola IBRLCM127 exhibited a prominent anti-MRSA activity particularly against cell membrane of MRSA cells. This report was the first report concerning the antimicrobial potential of endophytic fungus C. ramicola recovered from local medicinal plant, C. mangga.