Vitamin C Enhances the Antibacterial Activity of Honey against Planktonic and Biofilm-Embedded Bacteria.

Juraj Majtan,Viktor Majtan,Marcela Bucekova,Martin Sojka,Helena Palenikova

doi:10.3390/molecules25040992

Abstract

Multifactorial antibacterial action is an important feature of honey; however, its bactericidal efficacy against biofilm-embedded bacteria is limited. The aim of this study was to investigate the impact of vitamin C (Vit C) on the antibacterial activity of natural honeys against planktonic as well as biofilm-embedded bacterial pathogens. The antibacterial activity of four honey samples supplemented with Vit C was expressed as the minimum inhibitory concentration (MIC). At sub-MICs, Vit C significantly increased the antibacterial activity of the tested honeys against Pseudomonas aeruginosa in planktonic cultures. However, after supplementation, honeydew honey, the most active honey, was ineffective against Staphylococcus aureus. On the other hand, when 100% honeydew honey was supplemented with Vit C (100 mg/g of honey) in a multispecies wound biofilm model, complete eradication of almost all bacterial isolates, including S. aureus, was observed. Furthermore, a mixture of honey and Vit C was partially effective against Enterococcus faecalis, whereas honey alone exhibited no antibacterial activity against this bacterium. Vit C counteracted hydrogen peroxide in honey solution and, thus, eliminated the major antibacterial compound present in honey. It is likely that a combination of honey with Vit C may trigger the intracellular production of reactive oxygen species in bacterial cells, but the exact cellular mechanisms warrant further investigations.

Highlights

Honey has been successfully used as a topical wound care product, with pronounced antibacterial, antibiofilm, and anti-inflammatory properties
Honeydew honey exhibited even higher inhibitory activity, with minimum inhibitory concentration (MIC) values ranging from 6% to 8% depending on the bacterial species, in comparison to its activity against P. aeruginosa (Figure 2)
We showed that supplementation of different types of honey with sub-MICs of vitamin C (Vit C) resulted in a significant enhancement of the antibacterial activity against

Summary

Introduction

Honey has been successfully used as a topical wound care product, with pronounced antibacterial, antibiofilm, and anti-inflammatory properties. A meta-analysis investigating the efficacy of honey in different types of wounds indicated that the relative effect of honey on wounds was unclear because the trials performed so far have been small, clinically heterogeneous, short, and highly biased [1,2,3,4,5]. Some systematic reviews and meta-analyses have indicated that honey dressings are superior in the treatment of diabetic foot ulcers or burns when compared to conventional dressings [6,7,8]. Further clinical trials using honey as a topical wound care product are highly needed to clarify this ambiguity.

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