Evaluation of synergistic and antibacterial activity of Xylaria curta against drug-resistant Staphylococcus aureus and Pseudomonas aeruginosa

Abstract

Drug resistance problems are increasing worldwide, and hence, there is a need to find novel sources of antimicrobial drugs. At present, natural products still remain the most important resources for discovering new drugs. The screening of natural bioactive compounds from macrofungi is a promising way to meet the increasing threat of drug-resistant strains of human pathogens. In this study, the macrofungus was collected during spring seasons from the soil in tropical evergreen forest of Courtallam, Western Ghats of South India. It was identified as Xylaria curta based on the morphological characteristics and confirmed by 18S ribosomal RNA (rRNA) sequence comparisons. Extracts of fruiting bodies of X. curta were obtained using hexane, ethyl acetate, and methanol solvents. Among them, the ethyl acetate extracts exhibited an effective antimicrobial activity against bacterial and fungal strains. The extracts were also analyzed for antibacterial activity against drug-resistant Staphylococcus aureus strains (1-10) and Pseudomonas aeruginosa strains (1-8). The extract showed a maximum inhibition zone of 23.2 mm, 22.4 mm, and 20.7 mm against P. aeruginosa strain 8, P. aeruginosa strain 1, and S. aureus strain 8, respectively. Further, the extract had an effective minimum inhibitory concentration (MIC) of 200 μg mL-1 against drug-resistant S. aureus strain 8. The fractional inhibitory concentration indices of fruiting body extract with vancomycin and ciprofloxacin were 0.22 and 0.46, respectively. These results indicate that the extract had significant synergistic action with vancomycin. Xylaria curta is a potential source for the development of new antibiotics. © 2012 Copyright 2012 Mycological Society of China.