Comparison of methods to determine antibacterial activity of honeys against Staphylococcus aureus

- Different methods were compared to propose a honey's antimicrobial activity protocol.
- Agar dilution, broth dilution and agar well diffusion methods were compared.
- Agar well diffusion and broth dilution methods should be used one after the other.
- Antimicrobial activity of 56 honeys from Spain was studied against St. aureus.
- Honeys from Lavandula sp. showed the lowest antimicrobial activities.

Nowadays, researching potentially functional properties of honey such as antimicrobial activity is interesting due to the overwhelming problem of bacteria strains resistant to antibiotics, and the expected higher value for honey that consumers constantly demand. In this research, we compared three different methods (agar dilution, broth dilution, as well as agar well diffusion), to analyse honey's antimicrobial activity against Staphylococcus aureus, using 56 unpasteurized honeys from different botanical origins. Agar well diffusion method showed to be a rapid and low cost screening method, using less medium and material, to distinguish the samples with and without antibacterial activity. Agar dilution and broth dilution procedures gave similar values. However, the latter proved to be faster and much more informative, providing with minimal antimicrobial and bactericidal concentrations. Higher values of antimicrobial activities were found in honeydew honeys, polyfloral honeys, Calluna vulgaris and Erica spp. honeys. Conversely, Lavandula spp. samples showed lower antimicrobial activity against Staphylococcus aureus.