Validation of a traditional preparation against multi-drug resistant Salmonella Typhi and its protective efficacy in S. Typhimurium infected mice

Abstract Shorea robusta Gaertn has been used for skin and intestinal ailments in Indian Traditional medicine; while two tribal communities used its tender leaves in ‘Meyadi-bukhar’ or long-term fever. This prompted us to validate the aqueous and methanol extracts of Shorea robusta tender leaves against wild- and multidrug-resistant clinical isolates of Salmonella enterica Serovar Typhi ( S . Typhi), the causative agent of typhoid fever. The antibacterial activity, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and growth inhibition were determined using disc diffusion, agar-and-broth dilution, dose- and time-response assays, along with the safety and protective efficacy in Balb/C mice, infected with S . Typhimurium. The MIC of the extract was 256–450 μg/ml against S . Typhi isolates, and 700 μg/ml for mouse virulent S . Typhimurium, while MBC was ≤512–1024 μg/ml. The growth curve revealed that the extract was bactericidal at 4–6 h of exposure. Toxicity study showed that the extract was safe up to 3000 mg/kg (p.o.). Moreover, it significantly (p > 0.01) protect the challenged (1.4 × 10 8  cfu/ml) mice at 93.75 (i.p.) and 300 mg/kg (p.o.) dose, compared to the infection control (distilled water treatment group). Collectively, our results confirmed the antibacterial potential of the test extracts against MDR-isolates of S . Typhi.