SUMMARY The methanolic root extract of tissue cultured Pluchea indica (L.) Less. was tested for itsantibacterial potentiality against 102 different strains of bacteria belonging to both Gram positiveand Gram negative groups. The bacteria could be arranged according to their decreasing order ofsensitivity as follows: Staphylococcus aureus, Vibrio cholerae, Bacillus spp. Vibrio parahaemolyticus,shigellae, Salmonella spp., and Escherichia coli. The extract was found to be bacteriostatic in natureagainst Salmonella typhimurium NCTC 74. When administered to Swiss strain of white mice at thedoses of 0.5 and 1.0 mg/kg body weight, the extract could significantly protect the animalschallenged with 50 MLD of S. typhimurium NCTC 74. According to the chi-square test, the in vivodata is highly significant (P < 0.001).Key words: Tissue cultured; Pluchea indica; Root; Antibacterial; Salmonella typhimurium NCTC 74 INTRODUCTION One of the major achievements of medical sciencehas been the control and management of infectiousdiseases. For a long period of time, plants havebeen a valuable source of natural products formaintaining human health, especially in the lastdecade, with more intensive studies for naturaltherapies. Thus plants should be thoroughlyinvestigated to better understand their properties,safety and efficiency. Again plant tissue cultureresearch is multi-dimensional and activities oftissue-cultured plants, if proven would no doubtrevolutionize medicinal plant research. The mainobjective of this study is to evaluate the in vitro andin vivo antibacterial activities of tissue culturedPluchea indica root extract against different bacterialvirulent stains including Salmonella typhimuriumNCTC 74. The plant Pluchea indica (L.) Less. (Family:Asteraceae) is an evergreen large shrub foundabundantly in salt marshes and mangrove swampsin Sunderbans (India), Bangladesh, Myanmar,China, Philippines, Malaysia, Tropical Asia andAustralia. In Indo-China the roots in decoctionprescribed in fevers as a diaphoretic and aninfusion of the leaves is given internally inlumbago (Kirtikar and Basu, 1999). The root andleaves are used in some area as astringent andantipyretics (Kirtikar and Basu, 1999). The plant isalso known to be used in rheumatoid arthritis(Chatterjee, 1996). Root extract has also beenevaluated for (Sen et al., 1991), antiulcer (Sen et al.,1993), and neuropharmacological (Thongpraditchote