Evaluation of tea tree oil physicochemical features and its antimicrobial activity against Cutibacterium acnes (Propionibacterium acnes) ATCC®6919

Introduction: Tea tree oil is an essential oil, recognized for its antimicrobial properties. Objective: To evaluate the composition, feature, and antimicrobial effect at 2% v/v, and its Minimal Inhibitory Concentration (MIC) against Cutibacterium acnes (Propionibacterium acnes). Materials and methods: Three different batches of tea tree oil were evaluated, characterizing its chemotype by gas chromatography and its 2% v/v antimicrobial activity against C. acnes by agar diffusion assay (guide M11-A8 CLSI). The three batches of tea tree oil evaluated presented desired chemotypes according to the standard ISO 4730, indicating that it is a high-quality product. In addition, the batches presented 30-40% of Terpinen-4-ol, a compound that favors its antimicrobial activity. The antimicrobial activity of all batches against C. acnes had a concentration dependent effect with microbial growth inhibitory activity in all 2% v/v assays. The MIC obtained for all the batches against C. acnes was 0.25% v/v. The antimicrobial activity of tea tree oil against this microorganism, has been previously reported with a minimum inhibitory concentration between 0.05% and 1.25% v/v, a range that covers the minimum inhibitory concentration obtained in this study. Conclusion: These results show the high quality of this product and its capacity as an antibacterial agent against C. acnes. New studies should be carried out both with other isolates of this microorganism coming from patients and in vivo in patients with acne vulgaris, to confirm the activity of this product and each of its components.