The aim of this study was to determine in vitro anti-Salmonella activity of extracts of five selected Kenyan medicinal plants against Salmonella ser. Typhi and Salmonella ser. Typhimurium. The extracts from Tithonia diversifolia, Warburgia ugandesis, Croton megalocarpus, Carissa edulis and Launae cornuta plants traditionally used in treatment of typhoid fever were screened for anti-Salmonella activity using disc diffusion and microdilution techniques. The results from the present study have shown that out of thirty six extracts investigated, only nine extracts from T. diversifolia and W. ugendensis showed activity against Salmonella ser. Typhi and Salmonella ser. Typhimurium at 1000 mg/ml. The inhibition zone of ethyl acetate, hexane and methanol extracts of T. diversifolia leaves, ethyl acetate and hexane extracts of T. diversifolia flowers, ethyl acetate and hexane extracts of W. ugandensis stem barks, ethyl acetate and hexane extract of W. ugandensis roots ranged from 8 to 18.5 ± 0 mm. These results were comparable with those of ciprofloxacin (19.67 to 26 mm) and chloramphenicol (6.67 to 24.33 mm). The minimum inhibitory concentration (MIC) of the active extracts were in the range of 0.031 to 15.63 mg/ml which compared very well with ciprofloxacin (0.015 to 0.02) and chloramphenicol (0.022 to 0.03 mg/ml). Extracts with anti-Salmonella activity can be used to source antibiotic substances useful in the treatment of typhoid fever. The study provides the scientific basis for the traditional application against typhoid fever.
Key words: Anti-Salmonella activity, medicinal plant extracts, minimum inhibitory concentration, disc diffusion technique, microdilution technique, Salmonella strains, typhoid.
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