In-vitro antimicrobial efficacy of Sri Lankan bee honey against microorganisms causing chronic wounds

Abstract

Objectives: To evaluate the in-vitro efficacy of Sri Lankan bee honey as an antimicrobial agent against
pathogens causing chronic wounds.
Methods: Standard strains of 4 bacterial and 4 fungal species and fourteen bacterial isolates from
chronic wounds were tested against twelve honey types belonging to seven Agro Ecological Regions
(AERs). Antibacterial activity was determined by agar well diffusion, phenol equivalent methods and
Minimum Inhibitory Concentration (MIC) by agar dilution.
Results: 6/12, 5/12, 11/12 and 11/12 honeys gave inhibitory zones ranging 12.5-19.5 mm for
Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922), Pseudomonas aeruginosa
(ATCC-27853) and Klebsiella pneumoniae (ATCC-700603) respectively. All ATCC strains had MIC
of 10-20%. Out of six selected honeys, four gave therapeutic level activity for all tested clinical isolates
except for Pseudomonas aeruginosa. Phenol equivalence values ranged 12-18% and 14-28% (w/v) for
tested gram negative and positive bacterial species respectively. Honey originated from low country
regions reported phenol equivalence of 11-20% and superior activity against multidrug resistant
bacteria. Commercially available honey reported lowest antibacterial activity with 5-10% phenol
equivalence against 11/14 isolates. No inhibitory zones were observed for fungal species and MIC was
>40% for all types of honey.
Conclusions: Sri Lankan bee honey exhibits significant antibacterial activity against both gram positive
and negative bacteria including multidrug resistant organisms in-vitro. Antibacterial potency varies in
different types of honey from different AERs. Low country honey was superior to others while
antibacterial activity of commercially available honey was negligible. None of the honeys had
antifungal activity against Candida species.