Abstract
Infections caused by bacteria continue to be a major threat to public health. The impact of this is especially alarming in developing countries due to the relative shortages of medicines and the emergence of widespread drug resistance. This has led to the search for new antimicrobial agents mainly among plant extracts. As part of an ongoing research to isolate and purify antibacterial compounds from the extract of traditionally used medicinal plants from Kebbi State, Nigeria, some selected plants were screened for their antibacterial potentials. The preliminary phytochemical screening of the extracts was carried out using standard methods. The bioactivity (antibacterial) test was done using agar well diffusion method, while MIC and MBC were tested using broth dilution method. The results for the phytochemical screening showed the presence of flavonoids, tannins, saponins, glycosides, alkaloids and terpenoids in the selected plants extracts. The results for the antibacterial activity of the crude methanolic extracts of the
selected plants showed varying degree of antibacterial activities against selected bacterial isolates. However, the stem bark extract of Acacia nilotica showed relatively high zone of inhibition (mm), minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). The extract was found to inhibit the growth of most of the tested bacterial isolates comprising of both Gram-positive and Gram-negative organisms. These findings support previous reports on the antimicrobial activity of this plant. The result of the present study signifies the potential of Acacia nilotica stem bark as a source of therapeutic agents, which may provide leads in the ongoing search for antibacterial agents from plants.

Key words: plant extracts, methanol, phytochemicals, anti-bacterial activity, stem bark.