Abstract

Antibacterial activity of four different extracts from the stem bark of Acacia mearnsii was measured against five Gram-positive and five Gram-negative bacterial strains: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Micrococcus kristinae, Streptococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Shigella flexneri, Klebsiella pneumonia and Serratia marcescens. The extracts assessed include hexane, ethyl acetate, dichloromethane and methanol. The hexane, ethyl acetate and methanol extracts showed some inhibitory effects on the selected bacteria. The hexane extract showed some activity against four Gram-positive and two Gram-negative bacterial strains, but was not active against one Gram-positive and three Gram-negative bacterial strains. The ethyl acetate extract was effective against all the bacterial strains used in this study. The methanolic extract was effective against all the Gram-positive bacterial strains but it was not active against the Gram-negative bacterial strains except Escherichia coli. The dichloromethane extract was not active at all against all the bacterial strains tested. 

Key words: Acacia mearnsii, antibacterial activity, bacteria species.