Evaluation of Efficacy of Canadian Honeys Against Wound-Infecting Bacteria in vitro
[Note: The results of this study were presented at the recent convention of the Ontario Beekeepers’ Association in Niagara Falls, Canada.]
Authors: Katrina Brudzynski, Robert Lanningan
Brock University, St. Catharines, Ontario, Canada, London Health Sciences Centre, London, Ontario, Canada
Honeys possessing antibacterial activity have been demonstrated to be useful as an adjunct topical treatment of infected wounds and burns. Canadian honeys have been shown to posses antibacterial activity against two standard bacterial species, Gram-negative Escherichia coli (ATCC 14948) and Gram-positive Bacillus subtilis (ATCC 6633), however their activity against wound-infecting bacteria have not been adequately investigated yet.
Purpose: To evaluate the susceptibility of seven clinical isolates from infected wounds to Canadian honeys in vitro.
Methodology: The isolates included four different strains of Methicillin Resistant Staphylococcus aureus (MRSA), two strains of Vancomycin resistant Enterococcus faecium and Escherichia coli. A broth microdilution method was employed to establish the MIC 90 for each isolate against seven honeys derived from different plant sources. Isolates were identified to genus and species and their susceptibility to antibiotics was confirmed using an automated system (Vitek R, Biomérieux R). The presence of the Mec A gene, Nuc gene and Van A and B genes were confirmed by polymerase chain reaction.
Results: The antibacterial assays showed that all bacterial isolates tested were susceptible to honey action. The most susceptible to honeys were two strains of MRSA (MRSA #3 and #5), the least susceptible was E. coli from wound. The antibacterial potency of honeys against clinical isolates depended on their plant origin, with the monofloral honeys (buckwheat and blueberry) reaching MIC90 values of 6.25 % (v/v) to 12.5% (v/v).
Conclusions: Canadian honeys showed efficacy against both the standard bacterial species as well as the antibiotic-resistant clinical isolates from wounds. Therefore, the mechanism of honey action did not discriminate against susceptible versus resistant bacterial species. Buckwheat and blueberry honeys were consistently the most active honeys suggesting that the phytochemical compound(s) might be responsible for the activity. These results strongly suggest that some monofloral Canadian honeys are promising antimicrobial agents in treatment of infected wounds including those infected with MRSA and VRE.