Defeating biofilm: the role of essential oils in the battle against extensively drug resistant Pseudomonas aeruginosa
Mr Robbie Haines1, Dr Papanin Putsathit2, Dr Anna Tai3,4,5, Dr Katherine Hammer1
1School of Biomedical Sciences, University Of Western Australia, NEDLANDS, Australia
2School of Medical and Health Sciences, Edith Cowan University, JOONDALUP, Australia
3Department of Respiratory Medicine, Sir Charles Gairdner Hospital, NEDLANDS, Australia
4Institute for Respiratory Health, NEDLANDS, Australia
5Medical School, The University of Western Australia, CRAWLEY, Australia
Background: Cystic fibrosis-associated Pseudomonas aeruginosa (CFPA) is a source of significant morbidity and mortality in CF patients. Multidrug resistance (MDR), the capacity to form biofilms, and immune evasion mechanisms are key features of CFPA that enable the successful colonisation of lungs. Current treatments for MDR CFPA are inadequate, and novel approaches are required. In this study, we evaluated the interaction of essential oils and commonly nebulised/inhaled antibiotics when used against MDR CFPA.
Methods: Minimum inhibitory concentrations (MICs) and fractional inhibitory concentration indices (FICIs) of tea tree oil (TTO), tobramycin, colistin, and aztreonam were determined for clinical CFPA isolates (n=20) using a modified broth microdilution assay. The minimum biofilm eradication concentration (MBEC) and fractional biofilm eradication concentration index (FBECI) were also determined using a similar method, with biofilms formed on a purpose-built device (MBEC assay®).
Results: TTO was effective at lower concentrations against MDR CFPA isolates (n=3) that were in a biofilm than they were in a planktonic state (MBEC 8-16 times lower than MIC). CFPA within biofilm was less susceptible to aztreonam and colistin compared to planktonic cells (MBEC 4-16 times higher than MIC) but not tobramycin (MBEC 1-4 times MIC). When tested against CFPA isolates (n=3) in biofilm, TTO/aztreonam and TTO/colistin had indifferent relationships (FBECI 0.58-1.13, 0.46-0.69 respectively), whereas TTO/tobramycin had a synergistic relationship (FBECI 0.43-0.47).
Conclusion: The anti-biofilm properties of TTO and the synergistic relationship seen between TTO and tobramycin against CFPA in vitro make inhaled TTO a promising candidate as a potential therapeutic agent.
Biography:
Former critical care nurse and recent Master of Infectious Diseases graduate with research interests in AMR, bacterial HAIs, and with a particular focus on biofilm forming organisms.