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.