Evaluation of antibacterial activity of some medicinal plants on common enteric food-borne pathogens

Enterobacteria are often responsible for various gastrointestinal foods borne infection in humans especially in the developing countries. Cassia occidentalis, Croton zambensicus and Newbouldia leavis known as 'Ewe ori esi', Ajekobale and Akoko respectively in Yoruba are three plants whose leaves are used in combination by boiling to treat gastrointestinal and diarrhea illnesses among indigenes of Akungba-Akoko, Ondo State, Nigeria. The leave extracts from these medicinal plants were screened in vitro in the laboratory for their antibacterial activity against two prominent enteric bacteria, that is, Escherichia coli and Salmonella typhimurium using the agar disc diffusion method. The tyndalized leave extract of C. zambesicus showing antibacterial inhibition zone of 4 and 2 mm against S. typhimurium and E. coli respectively exhibited highest activity during the study than the autoclaved samples and other plant sources tested independently or combined, showing that the combinations of the extract samples do not exhibit synergistic effects. C. zambesicus can however be optimized clinically for chemotherapeutic control of these food-borne enteric infections.