In vitro Antimicrobial Activity of Commercially Available Melaleuca alternifolia (Tea Tree) Oil on Some Selected Clinical Pathogens

Aim: To evaluate the In vitro antimicrobial activity of Melaleuca alternifolia oil (tea tree oil), (TTO) on selected clinical isolates of fungi and bacteria, including some multidrug resistant strains commonly associated with nosocomial infection. Study Design: Laboratory experimental study. Place and Duration of Study: Public Health England (PHE), Microbiology laboratory, Southampton University Hospital, England, May 2014. Methodology: Three different concentrations (1%, 5% and 10%) of commercially available TTO were prepared (%v/v). Using an improvised disc diffusion antibiotic susceptibility testing method, the activity of TTO was tested against pure reference strains of Staphylococcus aureus ATCC 25923, Escherichia coli ATCC 25922, clinical isolates of Candida albicans, Pseudomonas aeruginosa, Streptococcus pyogenes, Bacteroides fragilis, methicillin- resistant Staphylococcus aureus (MRSA), extended spectrum beta lactamase Escherichia coli (ESBL) vancomycin-resistant Enterococcus faecium (VRE), and Carbapenemase-producing Klebsiella pneumoniae (CRKP). The zones of inhibition were measure for each organism at the various concentrations of TTO. Results: All the organisms tested showed susceptibility to TTO at concentration range of 5% - 10%, except Pseudomonas aeruginosa. Staphylococcus aureus ATCC 25923, MRSA, and VRE did not show any susceptibility at TTO concentration of 1%. The zones of inhibition for the susceptible organisms ranged between 10mm-19mm at 5% concentration and 15 mm- 36 mm at 10% concentration of TTO. Conclusion: TTO has a broad spectrum of In vitro activity against clinical pathogens. The essential oil or its active ingredient could be of potential benefit in the treatment of fungal, common bacterial and multidrug-resistant bacteria usually associated with hospital-acquired infections as well as mixed bacterial infections involving anaerobic bacteria.