Thesis (Ph.D.) - Cairo University - Faculty of Pharmacy - Department of Microbiology and Immunology

Antibiotics are often prescribed in acne treatment. However, Propionibacterium acnes and Staphylococcus epidermidis, the two major acne-associated bacteria, had developed antibiotic resistance. Essential oils (EOs) present a natural, safe, efficacious and multifunctional alternative treatment. Therefore, this study aimed to assess the potential anti-acne activity of selected seven EOs used commonly in Mediterranean folk medicine. Essential oils used were oregano, thyme, tea tree, lemongrass, lavender, mentha, and chamomile. Initial screening of the EOs antimicrobial activity was done using the paper disc diffusion method. Oregano at 1.4% concentration exhibited the highest antibacterial activity among tested EOs with inhibition zones of 31.7 mm against P. acnes and 30.7 mm against S. epidermidis. While thyme, lemon grass and tea tree at 1.4% concentration of EOs inhibited the growth of P. acnes with inhibition zones 23.3, 19.7 and 17.7 mm respectively. Meanwhile these three EOs inhibited the growth of S. epidermidis with inhibition zones 21.7, 17.3 and 13.7 mm respectively. Broth microdilution method was used to determine the minimum inhibitory concentration (MIC) of the tested EOs. Oregano EO exhibited the strongest antimicrobial activity with MIC 0.34 and 0.67 mg/mL against P. acnes and S. epidermidis, respectively. Thyme, lemon grass and tea tree EOs displayed MICs at 0.65, 1.22, and 1.28 mg/mL against P. acnes and 1.3, 1.22, and 1.28 against S. epidermidis, respectively acnes and S. epidermidis, respectively

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