The disc diffusion method, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and gradient-plate techniques were implemented to evaluate the antibacterial activity of honey and propolis against Staphylococcus aureusand Escherichia coli. The growth of S. aureus was inhibited by application of propolis and honey at concentrations of 2.74 to 5.48 mg ml-1 and 375.0 at mg ml-1, respectively at both MIC and MBC. The greater inhibition zones (13.0 ± 0.09 to 15.0 ± 0.11 mm) were observed from propolis at concentrations of 2.74 to 5.48 mg ml-1 in the disc diffusion method which was closely correlated with the MIC, MBC and gradient-plate technique results. The combined results obtained from the disc diffusion test, MIC, MBC and gradient-plate techniques suggested that propolis at concentrations of 2.74 to 3.5 and 3.5 mg ml-1 was effective to inhibit S. aureus and E. coli, respectively. On the contrary, honey was effective to inhibit S. aureus at the concentration of 375.0 mg ml-1 but failed to inhibit E. coli growth at same concentration. The combined results from all methods indicated that both propolis and honey had antibacterial activity against S. aureus. Present findings also suggested that S. aureus is more susceptible to the effect of the propolis than its Gram-negative counterpart E. coli.
Key words: Antibacterial activity, honey, propolis, MIC, MBC, disc diffusion, Escherichia coli, Staphylococcus aureus
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