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The effects of extracts of some indigenous South African plants on in vitro cultures of Brucella abortus
Polar and non-polar crude extracts of medicinal plants including Dicerocaryum eriocarpum (Pedaliaceae), Pterocarpus angolensis (Fabaceae), Schkuhria pinnata (Laminaceae) and Ziziphus mucronata (Rhamnaceae) used by small-scale farmers in South Africa for treatment of reproductive and postpartum ailments were tested for their antibacterial activities in the perceived Brucella abortus infection in cattle. The microplate method for minimum inhibitory concentration (MIC) determination  was used on in vitro cultures of Brucella abortus bacteria. The MIC results were determined and subsequent Total Activities (TA) were calculated. S. pinnata was the most effective with all the six extracts being active at a concentration equals or lower than 63mg/ml followed by D. eriocarpum with four active extracts. S. pinnata had also the highest Total Activity averaging 94.7. However, cattle suffering from bovine brucellosis are not generally treated because Brucella spp. may undergo L-transformation when exposed to certain antibiotics such as Penicillins and Oxytetracyclines . Decoctions and infusions used by farmers being less effective than these antibiotics on Brucella spp., it is therefore suspected that they would induce L-forms. For instance, the MIC for the positive control (Neomycin) was 0.3–2.4µg/ml as compared to S. pinnata extracts with their lowest effective MIC values at 31mg/ml. L-forms grow indefinitely with or without cell wall. The effects of such wall deficient forms on serological detection should be investigated in cattle herds because humoral immune response is principally directed against the O-PS moiety of the smooth lipopolysaccharide (S-LPS) or outer membrane proteins.
Acknowledgements: ARC – Onderstepoort Veterinary Institute, South Africa
References: 1. Eloff, J.N. (1998) Planta Medica 64:711–713.
2. Godfroid, J. et al. (2004) Bovine brucellosis. In: Infectious Diseases of Livestock, J.A. Coetzer & R.C. Tustin (Eds.), Oxford University Press.