Antimicrobial efficacy of liposome-encapsulated silver ions and tea tree oil against Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans
Version of Record online: 3 MAY 2013
© 2013 The Society for Applied Microbiology
Letters in Applied Microbiology
Volume 57, Issue 1, pages 33–39, July 2013
How to Cite
Low, W.L., Martin, C., Hill, D.J. and Kenward, M.A. (2013), Antimicrobial efficacy of liposome-encapsulated silver ions and tea tree oil against Pseudomonas aeruginosa, Staphylococcus aureus and Candida albicans. Letters in Applied Microbiology, 57: 33–39. doi: 10.1111/lam.12082
- Issue online: 12 JUN 2013
- Version of Record online: 3 MAY 2013
- Accepted manuscript online: 12 APR 2013 09:32AM EST
- Manuscript Accepted: 13 MAR 2013
- Manuscript Revised: 3 MAR 2013
- Manuscript Received: 14 DEC 2012
- silver ions;
- tea tree oil
The activity of alternative antimicrobial agents such as tea tree oil (TTO) and silver ions (Ag+) with multiple target sites impedes the development of antibacterial resistance and might be useful in improving the current treatment strategies for various chronic wound infections. In this study, liposome-encapsulated TTO, Ag+ and TTO plus Ag+ were added to suspension cultures of Pseudomonas aeruginosa (Ps. aeruginosa), Staphylococcus aureus (Staph. aureus) and Candida albicans (C. albicans). Treatment of these cultures using the agents in combination at subminimal lethal concentrations resulted in an enhanced loss of viability compared to treatment with individual agents. The effective concentration, elimination time (to the limit of detection, LOD) and fractional lethal concentration index (FLCI) of liposomal agents in combination were as follows:
Candida albicans: 0·05% v/v TTO:PVA30-70 kDa: 8·9 × 10−5% w/v Ag+:PVA30–70 kDa: 2·0 h, FLCI = 0·73 (indifferent),
Staphylococcus aureus: 0·05% v/v TTO:PVA30–70 kDa: 6·0 × 10−4% w/v Ag+:PVA30–70 kDa: 1·5 h, FLCI = 0·38 (synergistic),
Pseudomonas aeruginosa: 0·25% v/v TTO:PVA30–70 kDa: 3·2 × 10−4% w/v Ag+:PVA30–70 kDa: 30 min, FLCI = 0·33 (synergistic).
These results show the potential for improving antimicrobial efficacy by delivering lower effective concentrations of alternative agents, via controlled release systems. NB All values denoted as %w/vAg+ refer to the concentration of silver ions.
Significance and Impact of the Study
In this study, we have shown that encapsulating silver (as the ion Ag+) and tea tree oil (singly and in combination) in a controlled release liposomal carrier system can improve their antimicrobial efficacy as well as reduce the effective concentration required. These findings may impact on the problems of agent toxicity caused by the need for high effective doses or microbial resistance where long term application is required.