The synergistic effect of Alocasia longiloba Miq. Fruit’s Extract with Ampicillin and Tetracycline against bacteria

The inappropriate usage of antibiotic is one of the factor of the emergence of the antibiotic resistance bacteria that will limit the effectiveness of the current antibiotic and lead to the treatment failure. In recent years, there has been growing interest to evaluate plant possessing antibacterial activity for various disease. The combination of plant extract with antibiotic approach may lead to the new ways in the treatment of the infectious diseases and this combination may reduce of bacterial resistance toward antibiotics. The objectives of this study was to determine the synergistic effect of Alocasia longiloba Miq. fruit extract with ampicillin and tetracycline against Staphylococcus aureus and Escherichia coli. The synergistic effect of Alocasia longiloba Miq. fruit extract and antibiotics was determined by using agar well diffusion and minimal inhibitory concentration (MIC) Resazurin 96-well microdilution methods. The fruit extract of Alocasia longiloba Miq. showed no inhibition against both gram positive and gram negative bacteria. The results of this study showed the increasing in the inhibition zone when the plant extract was combined with ampicillin against E. coli. The other combination showed no increasing in the inhibition zone and some of it will reduce the inhibition zone compared to the individual effect of the antibiotic. The value of MIC only showed by ampicillin on E. coli which was 12.5 µg/ml, and the combination of plant extract and ampicillin (2000+12.5 µg/ml). The fractional inhibitory concentration (FIC) index cannot be determined due to the lacked of MIC value. These results indicated that the fruit extract of Alocasia longiloba Miq. showed low antibacterial activity against E. coli and S. aureus and this plant extract may show the inhibition if the concentration is increase and test against the different microorganisms.