Typhoid fever is a prolonged febrile illness caused by bacterium Salmonella typhi. It is acute generalized infection of reticuloendothelial system, intestinal lymphoid tissue and gall bladder. Salmonellosis can be experimentally induced in mice by Salmonella typhimurium. The pathogenesis of enteric fever has been studied using S. typhimurium infection in mouse as the animal model and for S. typhi in naturally infected humans and in volunteers. Typhoid fever is characterized with high fever with chills, diarrhoea, inflammatory response in the peyer’s patches, enterocolitis, headache, anorexia, weakness, dizziness, muscle pain, abdominal cramps, liver damage and change in the level of enzymes of oxidative stress. The treatment used against this disease was antibiotic and vaccination which has severe side effect. This lead us to explore natural plant products which is cheap, easily available and has no side effects.

         In the present study a number of plants extracts were screened out for their antisalmonellae activity in vitro against S. typhi and S. typhimurium. Six plants exhibit antisalmonella activity showing a very clear zone of inhibition. Extracts obtained from Emblica officinalis and Terminalia chebula exhibit potent antisalmonellae activity as indicated by their zone of inhibition. Minimum inhibitory concentration (MIC) of the above two plants extracts were then determined against S. typhimurium. The result encouraged to perform bactericidal kinetic assay by using the lyophilized juice of Emblica officinalis (EO) and water extract of Terminalia chebula (T) against S. typhimurium. EO at a concentration of 5 mg/ml exhibits no effect where as 10 mg/ml of it was bacteriostatic for 10 hour and then it retards the growth of bacteria. The same extract at a dose of 20 mg/ml was bactericidal. T at a dose of 10,12 and 15 mg/ml was bacteriostatic and above 15 mg/ml was highly bactericidal. The above in vitro study claimed the drugs to be used against S. typhimurium infection in vivo.

          Animals (mice) pretreated with lyophilized juice of Emblica officinalis at a dose of 500 mg/kg body wt (EO500) for 30 days exhibit full protection against 2x LD50 dose of S. typhimurium where as pretreatment with water extract of Terminalia chebula at a dose of 500 mg/kg body wt (T500) for 30 days exhibit full protection against 1x LD50 dose of S. typhimurium. Studying the clearance of bacteria from reticuloendothelial system and serum enzymes viz, SGPT and SGOT then supported this study.

          Animals pretreated with EO500 and T500 for a period of 30 days followed by challenge with sublethal dose of S. typhimurium exhibit an increase in the total leucocytes and lymphocyte count. Delayed type of hypersensitivity is considered as an in vivo manifestation of cell-mediated immune response, and development of a positive DTH reaction is correlated with protective cell-mediated immune response. Treatment with EO500 and T500 exhibit an increase in foot pad swelling significantly (p<0.01) as compared to saline treated control animals at 48 hour followed by a decrease in swelling at 72 hour.

          Both the above doses of drugs exhibit an increase in lymphocyte proliferation against S. typhimurium. Thus both plant exhibit immunomodulatory activity against experimentally induced salmonellosis.

          There is imbalance in the level of enzymes of oxidative stress viz lipid peroxidation, xanthine oxidase, catalase, glutathione content, glutathione peroxidase and glutathione reductase when the animals were infected with S. typhimurium. Animals pretreated with EO500 and T500 followed by challenge with S. typhimurium nullifies the effect produced on the enzymes of oxidative stress.

          Both EO and T exhibit pharmacological activity viz anti-inflammatory, antipyretic and analgesic activities.

          Thus the above plants extract exhibit antisalmonellae activity. Pretreatment of animals with the above drugs prevent the animals from salmonellosis by immunomodulation as well as balancing the level of enzymes of oxidative stress and through various pharmacological activities