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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.

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Background Typhoid fever (enteric fever) is caused by Salmonella typhi which is solely a human pathogen with no known animal reservoir. S. typhi is a gram-negative, motile, rod-shaped and facultative anaerobic bacterium. 1 It is a non-spore forming and non-lactose fermenting bacterium. The bacterium is transmitted mainly through consumption of food and water that has been contaminated by faecal matter. 2 Clean water, good hygiene and sanitation are factors that prevent the spread of typhoid. 1,3,4 The incubation period is usually 1-2 weeks, and the duration of the illness is about 3-4 weeks. Symptoms include poor appetite, headaches, generalized aches and pains, fatigue, weakness, fever as high as 103 o to 104 o F (39°C to 40°C), lethargy, diarrhoea and rose coloured spot. 5,6 Salmonella typhi infection begins with colonization of the small intestine, which progresses to the invasion of the gastrointestinal mucosa. The infection then spreads to the liver, spleen, and bone marrow. 1,7 The severity of the infection depends on the initial infective dose, virulence and the host's immune response. 8-10 The greatest burden of disease is experienced by infants, children and adolescents (the World Health Organization [WHO] 11 and Crump and Mintz 12). In view of the above, the WHO recognizes this disease as a major public health problem and recommends immunization with Vi polysaccharide vaccine in high-risk areas. 13 Typhoid fever is an endemic disease in tropical and subtropical climates and has become a major public health problem in developing countries, with an estimated annual incidence of 540 cases per 100 000 people, and an estimated 17 million cases worldwide. 11,14 It is often encountered in tropical countries including Nigeria where it constitutes a serious source of morbidity and mortality. 15,16 This stems from poor hygienic environment and inadequate water supply systems which have become

One hundred and thirty-five water samples were collected from five fresh water bodies in three locations in Benue State, Nigeria and screened for the occurrence of Bdellovibrio spp. using the double layer agar technique. E. coli, S. typhi and Shigella spp. were used as prey bacteria. All water bodies sampled had average temperatures ranges of 26-27°C. pH values ranged between 7 and 8. Total hardness values ranged between 48 and 85 mg LG 1 , while TDO values were between 5.0 and 15.3 mg LG 1. A total of 53 Bdellovibrio PFUs occurred with the following frequencies on respective host prey; 42 (79.2%) on E. coli, 10 (18.86%) on S. typhi and 1 (1.88%) on Shigella spp. More research on Bdellovibrio occurrence in other niches in Nigeria is advocated to better understand the dynamics of these unique bacteria in a bid to harness its potential as control for Gram negative infections.