Planta Med 2007; 73 - P_186
DOI: 10.1055/s-2007-986967

Bovine tuberculosis: a zoonotic target for medicinal plants

LJ McGaw 1, N Lall 2, T Hlokwe 3, A Michel 3, JJM Meyer 2, JN Eloff 1
  • 1Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Private Bag X04 Onderstepoort 0110, South Africa
  • 2Department of Botany, University of Pretoria, Hatfield Pretoria 0002, South Africa
  • 3Tuberculosis Laboratory, ARC-Onderstepoort Veterinary Institute, Private Bag X5 Onderstepoort 0110, South Africa

Bovine tuberculosis (TB), caused by Mycobacterium bovis, is an important zoonotic disease that can spread to humans, especially immunocompromised individuals, through infected livestock products including unpasteurised milk. In southern Africa, medicinal plants are employed to relieve TB-related symptoms such as chest complaints and coughing, for example root preparations of Euclea undulata and E. natalensis. These plants, and compounds isolated from them, are known to have activity against M. tuberculosis. The objective of this study was to determine firstly the activity of E. undulata and E. natalensis species against infective M. bovis, and secondly the extent to which the non-pathogenic vaccine strain, M. bovis BCG, can be used as a model for detection of activity against slow-growing pathogenic Mycobacterium species. Activity against two fast-growing saprophytic species, M. smegmatis and M. fortuitum, was also evaluated. Extracts of E. undulata and E. natalensis roots were tested for antimycobacterial activity against M. bovis ATCC 19210, M. bovis BCG, M. smegmatis and M. fortuitum using a twofold serial dilution assay in microtitre plates. A compound with known antimycobacterial activity present in both Euclea species, diospyrin, was included in the assays. The anti-TB drug isoniazid was used as a positive control. After incubation, MIC values were detected using a tetrazolium salt indicator. MICs of the plant extracts and diospyrin were similar against the M. bovis slow-growing strains, with MICs ranging between 5.70 and 16.28µg/ml. Against the fast-growers, the MIC for the extracts was approximately 300µg/ml and for diospyrin 15.63–62.50µg/ml. In conclusion, it was shown in this instance that M. bovis BCG is a better model for antimycobacterial activity against M. bovis than M. smegmatis or M. fortuitum although it has the disadvantage of a slower growth rate.

Acknowledgements: Claude Leon Foundation, National Research Foundation (South Africa).