Purpose:The purpose of the study is to evaluate the antimicrobial and antitumor activities of Stevia rebaudiana (Asteraceae) leaf extracts. Methods: Four solvent extracts (ethyl acetate, acetone, chloroform and water) of Stevia rebaudiana leaves were investigated against Staphylococcus aureus, Salmonella typhi, Escherichia coli, Bacillus subtilis, Aeromonas hydrophila and Vibrio cholerae by using agar well diffusion method. Candida albicans, Cryptococcus neoformans, Trichophyton mentagrophytes and Epidermophyton species were used to test anti-yeast and antifungal activity. The cytotoxic effects of the extracts on Vero and HEp2 cells were assayed using 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide [MTT]. Results: Among the four extracts tested, acetone extract had effective antibacterial potential, followed by ethyl acetate extract. The acetone extract showed greater activity against Gram-positive than against Gram-negative organisms. All the extracts were active against Epidermophyton species and Candida albicans. The 1:8 dilution of the acetone extract was non-toxic to normal cells and also had both anticancer and anti-proliferative activities against cancerous cells. Conclusion: The study confirms the antimicrobial and antitumor activities of Stevia rebaudiana leaves extracted using various solvents, and is therefore, a potential drug that requires further studies and development.

The present study was conducted to determine the virulence and cytotoxicity of Aeromonas hydrophila strains isolated from seafood samples collected from 5 major fish markets in Chennai, Tamil Nadu, India. Among 73 A. hydrophila strains isolated from fish and shrimp samples, 86.3% exhibited haemolysis, 78.1% produced slime, 98.63% produced protease and also demonstrated cytotoxicity on Vero cells. Cell shrinkage, detachment and rounding of Vero cells were recorded as cytotoxic changes. Only one strain did not show haemolysis, slime production, proteolytic activity and cytotoxicity on treatment with Vero cells. Positive correlation was observed between proteolytic activity and cytotoxicity irrespective of haemolytic activity of the strains. These results demonstrated the presence of wide spread, pathogenically characterized, cytotoxic seafood borne A. hydrophila in Chennai

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