The antibacterial activities of the plants, Mitragyna inermis
, Morinda lucida
, Khaya senegalensis
and Nauclea latifolia
were investigated using an indicator-based microdilution technique. The extracts of the plants in water, methanol, chloroform and petroleum ether inhibited growth of bacteria in broth cultures. M. inermis
with the lowest minimal inhibitory concentration (MIC) of 0.03g/ml was the bacteriologically most active plant. The chi-square value (10.25) and F-statistic value (4.36) were significant at less than 0.05 level and implied that inhibition of bacterial growth was significantly associated with the type of plant investigated. The R value obtained on regressing bacterial inhibition on the independent variables - type of plant, plant part (leaf or stem bark) and extraction solvent used - was 0.57 (p < 0.01 level), and means that the independent variables put together influenced inhibition of bacterial growth . The findings of this study suggest the effectiveness of the microdilution technique in the phytochemical screening of plants for antibacterial activities.