In vitro anti-microbial activity of the essential oils and extracts in a plant-based skin cream

The investigational dermal cream (PID 02027030) is designed to soothe skin lesions of dogs, cats, and horses. The cream contains a mixture of plant extracts ( Arnica Montana L., Calendula officinalis L., Echinacea purpurea (L.) Moench, Hamamelis virginiana L.) and essential oils ( Lavandula officinalis Chaix ex Villars, Melaleuca quinquenervia (Cav.) S.T. Blake, Salvia lavendulifolia Vahl. and Thuja occidentalis L.) (8.25% v/w) in a non-natural excipient. The extracts and oils conform with the EU or French pharmacopeia (when available) and/or are standardized using marker compounds. In order to determine the anti-microbial activity of the cream, the mixture of plant-based oils and extracts (not in the excipients) was tested in vitro against 12 microorganisms ( Candida albicans (ATCC#90028), Epidermophytum floccosum , Malassezia pachydermatis , Microsporum canis , Psuedomonas aeruginosa (ATCC#27858), Saccharomyces cerevisiae (ATCC#2601), Trichophyton mentagrophytes , Trichophyton rubrum , Bacillus cereus (ATCC#11778), Escherichia coli (ATCC#25922), Helicobacter pylori and Staphylococcus aureus (ATCC#25923); Organisms without ATCC numbers were isolated from infected animals presented at the Cornell University Veterinary Clinics [1]). A modified National Committee for Clinical Laboratory Standards (NCCLS) method was used. To increase solubility of the oils, the growth media was prepared with 0.5% Tween 20 [2, 3]. Six mm diameter filter-paper discs were treated with 20µl of the mixture. Ethanol and chloramphenicol were used as controls. Plates of all bacteria were incubated for 24h at 37°C. Plates with fungi were incubated for 48h at 35°C. Microsporum canis was incubated for 72h at 35°C. The mixture was active against all test organisms at 20µl. It was more active against the fungi than the bacteria, with rings of growth inhibition ranging from irregular ( Malassezi pachydermatis ) to 1.5cm for the fungi and 0.8 for all of the bacteria. Based on these results, the dermal cream could be useful in preventing secondary infections in lesions. Acknowledgements : Novartis Animal Health Inc., Switzerland, Oystershell NV, Belgium References : 1. Timoney, J.F. et al. (eds) (1998), Hagan & Bruner's Microbiology and Infectious Diseases of Domestic Animals, 8th Ed. Comstock Publishing Association. Ithaca, NY. 2. Griffin, S.G. et al. (2000), J. Essent. Oil Res. 12: 249–255. 3. Jansen, A.M. et al. (1987), Planta Medica 53: 395–398.