Aled E L Roberts, Sarah E Maddocks and Rose A Cooper
The presence of Pseudomonas aeruginosa in surface wounds is of clinical significance and can lead to persistent infections. Manuka honey has gained ground in clinical settings due to its effective therapeutic action and broad spectrum of antibacterial activity. In this study, the effect of manuka honey on P. aeruginosa was investigated using MIC, MBC, growth kinetics, confocal microscopy, atomic force microscopy and real-time PCR. A bactericidal mode of action for manuka honey against P. aeruginosa was deduced (12% w/v MIC; 16% w/v MBC) and confirmed by confocal and atomic for microscopy, which showed extensive cell lysis after 60 minutes exposure to inhibitory concentrations of manuka honey. The inability of honey treated cells to form micro-colonies was demonstrated and investigated using Q-PCR for three key micro-colony forming genes: algD, lasR, and oprF. algD expression increased 18-fold whereas oprF expression decreased 8-fold following honey treatment; lasR expression remained unaltered. These findings confirm that manuka honey is effective at inducing cell lysis and identifies two targets, at the genetic level, that might be involved in this process.