ANTI-MRSA OF THE ETHYL ACETATE CRUDE EXTRACT FROM LASIODIPLODIA PSEUDOTHEOBROMAE IBRL OS-64, AN ENDOPHYTIC FUNGUS ISOLATED FROM LEAF OF OCIMUM SANCTUM LINN

摘要

Objective: To investigate the effects of ethyl acetate crude extract of an endophytic fungus, L. pseudotheobromae IBRL OS-64 which was isolated from leaf of Ocimum sanctum against the growth of methicillin-resistant Staphylococcus aureus (MRSA)., a common pathogenic bacteria to human. Methods: Minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) were determined. Time-kill assay was used to examine the effect of the extract on the MRSA growth profile. The effects of the extract on the ultrastructure of MRSA cells were analyzed by scanning electron microscopic (SEM) study. Results: The results obtained from this study showed the fungal ethyl acetate crude extract exhibited a strong bactericidal effect on MRSA where the ratio of MBC/MIC was 2 and less than 4. The MIC and MBC values were 125.0 and 250.0 μg/ml, respectively. The time-kill study revealed that the bacteriocidal activity of the extract was both concentration and time-dependent. After 12 h treatment, the interaction of extract with MRSA cells resulted in the formation of dents, cavity or small dimples on the cell surface, indicating disintegration of the cell wall and cell membrane that resulting in leakage of their cytoplasmic contents, and ultimately cell death. Conclusion: The ethyl acetate crude extract of L. pseudotheobromae IBRL OS-64 showed a significant anti-MRSA activity and principally affected the cell wall and the cell membrane of the growing MRSA cells. This is the first report on L. pseudotheobromae , an endophytic fungus isolated from medicinal herb, Ocimum sanctum Linn.