Antimicrobial effects of Melaleuca alternifolia (tea tree) essential oil against biofilm-forming multidrug-resistant cystic fibrosis-associated Pseudomonas aeruginosa as a single agent and in combination with commonly nebulized antibiotics
Document Type
Journal Article
Publication Title
Letters in Applied Microbiology
Volume
75
Issue
3
First Page
578
Last Page
587
PubMed ID
34687564
Publisher
Wiley
School
School of Medical and Health Sciences
RAS ID
42643
Funders
Conquer Cystic Fibrosis Research Grant
Abstract
Broth microdilution assays were used to determine minimum inhibitory concentrations (MICs) and fractional inhibitory concentration indices (FICIs) of tea tree oil (TTO), tobramycin, colistin and aztreonam (ATM) against clinical cystic fibrosis-associated Pseudomonas aeruginosa (CFPA) isolates (n = 20). The minimum biofilm eradication concentration (MBEC) and fractional biofilm eradication concentration index (FBECI) were also determined using a similar microbroth dilution checkerboard assay, with biofilms formed using the MBEC device®. TTO was effective at lower concentrations against multidrug-resistant (MDR) CFPA isolates (n = 3) in a biofilm compared to in a planktonic state (MBEC 18·7-fold lower than MIC). CFPA within biofilm was less susceptible to ATM, colistin and tobramycin compared to planktonic cells (MBEC 6·3-fold, 9·3-fold, and 2·1-fold higher than MIC respectively). All combinations of essential oil and antibiotic showed indifferent relationships (FICI 0·52–1·72) when tested against planktonic MDR CFPA isolates (n = 5). Against CFPA isolates (n = 3) in biofilm, combinations of TTO/aztreonam and TTO/colistin showed indifferent relationships (mean FBECI 0·85 and 0·60 respectively), whereas TTO/tobramycin showed a synergistic relationship (mean FBECI 0·42). The antibiofilm 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.
DOI
10.1111/lam.13589
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Comments
Haines, R. R., Putsathit, P., Tai, A. S., & Hammer, K. A. (2022). Antimicrobial effects of Melaleuca alternifolia (tea tree) essential oil against biofilm‐forming multidrug‐resistant cystic fibrosis‐associated Pseudomonas aeruginosa as a single agent and in combination with commonly nebulized antibiotics. Letters in Applied Microbiology, 75(3), 578-587. https://doi.org/10.1111/lam.13589