Objectives: The current study was performed to show the antibacterial effect of red betel (Piper crocatum Ruiz and Pav.) in combination with vancomycin against Staphylococcus aureus. The reduction of S. aureus susceptibility to vancomycin was reported in 1997. The combination of isolated antibacterial compounds from plant with antibacterial drug were expected to increase antibacterial activity resulted in the reduction of resistance. Methods: The antibacterial effect of red betel extract and vancomycin separately and the combination of both materials were evaluated based on the zone of inhibition diameter using agar diffusion method. The interaction effect of extract and antibiotic combination was performed using microdilution checkerboard method. Results: There was an antibacterial effect of red betel extract started at the concentration of 150 mg/ml. The combination of red betel extract with vancomycin showed significantly greater inhibition growth of S. aureus compared to those of red betel or vancomycin alone. The addition of red betel extract to vancomycin reduced Minimum Inhibitory Concentration (MIC) vancomycin to be a-4 fold reduction against S. aureus. Moreover, the Fractional Inhibitory Concentration Index (FICI) of red betel extract and vancomycin combination was 0.3125. Conclusion: There was a synergistic effect of the red betel extract in combination with vancomycin against S. aureus. It is the potential result for the future research on the infectious treatment of S. aureus resistant to vancomycin.
Key words: Piper crocatum, Vancomycin, Synergistic antibacterial, Staphylococcus aureus.