Antimicrobial activity of Aspergillus sp. IBRL MP15 CCL, an endophytic fungus isolated from Swietenia macrophylla leaf against human pathogens

Aims: Endophytes are microorganisms residing in the living tissues of the host plant and may contribute to their host plant by producing a plethora of bioactive compounds that provide survival value to the plant. This study aimed to evaluate the antimicrobial activity of Aspergillus sp. IBRL MP15 CCL, an endophytic fungus isolated from Swietenia macrophylla leaf. Methodology and results: The antimicrobial activity was evaluated with disc diffusion and a colorimetric broth microdilution test against 15 organisms comprising of 4 Gram-positive bacteria and 4 Gram-negative bacteria, 4 fungi and 3 yeast. On disc diffusion assay, the fungal extract was shown to inhibit the growth of 7 test bacteria and 3 test yeast. The antibacterial activity was more pronounced with extract from fungal culture with host plant extract supplementation with significantly larger inhibition zones on all susceptible test microorganisms. The minimal inhibitory concentration of the extract ranged from 250 to 4000 mu g/mL indicating different level of susceptibility of the tested pathogens against the fungal extract. The killing kinetic study shows that antimicrobial activity of the fungal extract is concentration dependent and it can act as bactericidal at higher concentration. Conclusion, significance and impact of study: The findings of this study suggest that Aspergillus sp. IBRL MP15 CCL can be a promising source of antimicrobial agent to be further studied and developed.