Journal of Microbial & Biochemical Technology

Abstract

The Effect of Selected Combretum Species from Zimbabwe on the Growth and Drug Efflux Systems of Mycobacterium aurum and Mycobacterium smegmatis

Ruvimbo Magwenzi, Colet Nyakunu and Stanley Mukanganyama

Treatment of tuberculosis has become a challenge due to the rapid increase of multidrug and extensive drug resistant Mycobacterium tuberculosis. Medicinal plants might represent a possible source for new potent antibacterials to which pathogen strains are not resistant. In this study, five Combretum plant species-Combretum imberbe, Combretum zeyheri, Combretum hereroense, Combretum elaeagnoides and Combretum platypetalum used in traditional medicine were exposed to susceptibility tests to determine the effects of drug accumulation in avirulent M. smegmatis and M. aurum. The MIC values of the potent plant species was then determined. Using the agar disc diffusion assay, it was found out that the only the ethanolic extract from Combretum imberbe was active on M. smegmatis and it had an MIC of 125 μg/ml in the broth microdilution assay. However, using Sabouraud dextrose broth, Combretum platypetalum was found to have antimycobacterial effects which were not detected when using the agar disc diffusion assay. MIC of 63 and 125 μg/ml and MBCs of 250 and 500 μg/ml were obtained for C. platypetalum for M. smegmatis and M. aurum respectively. C. imberbe extract gave an MIC of 125 μg/ml but did not produce MBCs suggesting that it is bacteriostatic and not bactericidal. Drug accumulation transport assays were performed on C. imberbe, C. hereroense and C. platypetalum and results show that extracts from two plants are efflux pump inhibitors. Determination of the IC50 for the transport process was as conducted on Combretum imberbe using CCCP as the standard inhibitor. Both plants extract in addition to C. hereroense maybe potential sources for leads for efflux pump inhibitor in mycobacteria.