Manuka honey inhibits siderophore production in Pseudomonas aeruginosa

Aims: The aim of this study was to determine whether manuka honey affected siderophore production by three strains of Pseudomonas aeruginosa. Methods and results: The minimum inhibitory concentration (MIC) of manuka honey against each of the test bacteria was determined. The effect of manuka honey on siderophore production by three strains of Ps. aeruginosa was investigated using the Chrome azurol S assay (CAS) and CAS-agar plates. Manuka honey at 1/2 and 1/4 of the MIC for each strain led to reduced production of siderophores (1·3-2·2-fold less) which was found to be statistically significant when compared to the untreated control. Conclusions: Manuka honey effectively inhibited siderophore production by all three strains of Ps. aeruginosa used in this study. This suggests that manuka honey may impact on bacterial iron homoeostasis and identified a new target for manuka honey in Ps. aeruginosa. Significance and impact of study: Pseudomonas aeruginosa is an opportunistic human pathogen that can cause acute, life-threatening or persistent wound infections. Part of the virulence repertoire of this micro-organism includes the ability to sequester iron from the host during infection by the synthesis and secretion of siderophores. Manuka honey may limit wound infection by Ps. aeruginosa by limiting its ability to capture iron. This is the first time this mechanism has been investigated.