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
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.
RAS ID
42643
Document Type
Journal Article
Date of Publication
9-15-2022
Volume
75
Issue
3
Funding Information
Conquer Cystic Fibrosis Research Grant
PubMed ID
34687564
School
School of Medical and Health Sciences
Copyright
subscription content
Publisher
Wiley
Recommended Citation
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. DOI: https://doi.org/10.1111/lam.13589
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