Evaluation of Topical Gel Bases Formulated with Various Essential Oils for Antibacterial Activity against Methicillin-Resistant Staphylococcus Aureus

Purpose: To formulate topical gels containing various essential oils and evaluate their antibacterial activity against methicillin-resistant Staphylococcus Aureus (MRSA) skin infections. Methods: The four essential oils namely, lemon grass, rosemary, thyme and basil were steam-distilled and then evaluated for their antibacterial activity against MRSA. Lemon grass and thyme oils were chosen for further studies, including analysis of their composition by gas chromatography-mass spectrometry (GC/MS). Gels were formulated using carbopol 940, hydroxypropylmethyl cellulose, sodium carboxymethy cellulose with lemon grass oil and evaluated for their physical appearance, pH, spreadability rheological properties, antibacterial activity against MRSA and skin irritation in human volunteers. The selected gels were prepared with thyme oil alone or in combination with lemon grass oil and compared with that containing lemon grass oil alone. Results: The minimum inhibitory concentration (MIC) of lemon grass and thyme oils were 30 and 4 mu l/ml, respectively. Carbopol 940 gel (0.75 %) containing lemon grass oil showed good physical characteristics, including spreadability and rheological properties; it also showed the strongest antibacterial activity of the gels tested. No significant difference (p <= 0.05), were observed between the characteristics of the gels containing thyme oil alone and in combination with lemon grass oil. The antibacterial activity of the gel containing the two oils was approximately the sum of those containing the individual oils. No signs or symptoms of lesions, redness or itching were found when the gels were applied to the skin. Conclusion: The carbopol 940 gel containing lemon grass and thyme oils possess good antibacterial activity against MRSA when applied to human skin, and exhibit no skin irritation.