Abstract

     Five plant species (Balanites maughamii, Breonadia salicina, Dombeya rotundifolia, Hyperacanthus amoenus and Piliostigma thonningii) were extracted with acetone. Antibacterial activity of the leaf extracts of B. maughamii and D. rotundifolia, P. thonningii and bark extracts of B. salicina and H. amoenus were determined using serial dilution assay. The plant species were selected based on information provided by small scale farmers on the use of these plant species against various diseases in the domestic livestock. The crude extracts were tested for antibacterial activity against four selected bacterial strains, one gram positive (Bacillus cereus ATCC 14579) and three gram negative (Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922 and Enterococcus faecalis ATCC 29212). All plant extracts were active against the selected tested bacterial. Of the five plant species, leaf extracts of B. maughamii and P. thonningii had the best antibacterial activity against E. faecalis and P. aeruginosa (MIC value of 0.195 mg/ml). However, addition of polyethylene glycol (PEG) to the plant extracts resulted in reduction of antibacterial activity in all crude extracts, with PEG being more effective than polyvinyl polypyrrolidone (PVPP). The highest percentage reduction (97.8%) was observed in extract of B. maughamii against E. faecalis. Bioautography assay was used to determine the number of antibacterial compounds in the extracts. No active compounds were observed in plant extract of P. thonningii with good antibacterial against microorganisms indicating possible synergism between separated metabolites. Based on our findings, selected plant species could be used by small scale farmers in ethnoveterinary medicine to combat bacterial infections in livestock.

Key words: Antibacterial activity, minimum inhibitory concentration, bioautography assay, ethnoveterinary medicine