Abstract

Emergence of multidrug resistant bacterial strains urged the investigation for alternative medicines. The present study was designed to evaluate the mode of action of the crude methanolic extract of Hemidesmus indicus root againstSalmonella typhimurium both in vivo and in vitro. Pounded root was soaked in methanol for 7 days in room temperature with three solvent changes. The extract was pooled together, distilled and concentrated. An insoluble fraction comprising terpenoides, steroids and fatty acids, abbreviated as ME1 (methanol extract 1) was isolated from the crude methanol extract of H. indicus root (MHI with tannins and glycosides as the major constituents) during extraction. This study deals with the effect of these crude extracts (ME1 and MHI) against S. typhimurium-induced pathogenesis. In vivo ileal loop model in rat, in vitro organ culture and in vivo multiplication of S. typhimurium were used in mouse model (n=6). Both ME1 and MHI treated bacteria had 3 - 4 foldless initial attachment to murine intestinal epithelium in comparison to the wild type bacteria. The in vivo multiplication rate of wild S. typhimurium in the liver and spleen of mice was 100 fold higher, which was considerably less for MHI treated bacteria and negligible for ME1 treated S. typhimurium. The rat ileum infected with wild bacteria was severely inflamed; whereas the ileum infected with ME1 treated S. typhimuriumwas almost normal in appearance. The rats pre administered with MHI and then infected with wild type bacteria had normal villi, which proved its protective role. The in vivo activity of the extracts was further confirmed in vitro by using various simulating growth conditions, which mimic host environment. The type III secretory proteins (TTSPs) were isolated from wild as well as extract treated S. typhimurium and compared. Both the extracts inhibited the secretory proteins encoded by SPI-1 (involved in invasion and enteritis) as well as SPI-2 (involved in intracellular survival and multiplication) considerably. Differential activity of different constituents was observed to protect rat intestine as MHI had prophylactic and ME1 had therapeutic activity.

Key words: Hemidesmus indicus root, ME1, MHI, SPI-1, SPI-2, Salmonellatyphimurium, type III secretory proteins (TTSPs).