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Open Access Highly Accessed Research

Synergistic antimicrobial activity between pentacyclic triterpenoids and antibiotics against Staphylococcus aureus strains

Pooi Yin Chung1, Parasakthi Navaratnam1* and Lip Yong Chung2

Author Affiliations

1 School of Medicine and Health Sciences, Monash University, Sunway Campus, Malaysia

2 Department of Pharmacy, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia

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Annals of Clinical Microbiology and Antimicrobials 2011, 10:25  doi:10.1186/1476-0711-10-25

Published: 9 June 2011

Abstract

Background

There has been considerable effort to discover plant-derived antibacterials against methicillin-resistant strains of Staphylococcus aureus (MRSA) which have developed resistance to most existing antibiotics, including the last line of defence, vancomycin. Pentacyclic triterpenoid, a biologically diverse plant-derived natural product, has been reported to show anti-staphylococcal activities. The objective of this study is to evaluate the interaction between three pentacyclic triterpenoid and standard antibiotics (methicillin and vancomycin) against reference strains of Staphylococcus aureus.

Methods and Results

The activity of the standard antibiotics and compounds on reference methicillin-sensitive and resistant strains of S. aureus were determined using the macrodilution broth method. The minimum inhibitory concentration (MIC) of the compounds was compared with that of the standard antibiotics. The interaction between any two antimicrobial agents was estimated by calculating the fractional inhibitory concentration (FIC index) of the combination. The various combinations of antibiotics and compounds reduced the MIC to a range of 0.05 to 50%.

Conclusion

Pentacyclic triterpenoids have shown anti-staphylococcal activities and although individually weaker than common antibiotics produced from bacteria and fungi, synergistically these compounds may use different mechanism of action or pathways to exert their antimicrobial effects, as implicated in the lowered MICs. Therefore, the use of current antibiotics could be maintained in their combination with plant-derived antibacterial agents as a therapeutic option in the treatment of S. aureus infections.