Live bacteria were prepared by culturing cells in 25 mL liquid LB medium at 37°C for 18 h followed by inoculation of 2.5 mL cultures into 25 mL liquid LB medium to produce 2 · 10 9 -5 · 10 9 CFU/mL. Live bacteria counting was performed by serial dilution of cultures followed by spread plating. Serotype O FMDV strain HKN/ 2002 passaged five times in suckling mice was used to challenge guinea pigs, and the virus passaged three times in swine was used for swine experiments. The viruses were titrated on guinea pigs and swine. The dose of FMDV used was determined through four 10-fold serial dilutions of virus (i.e. 10 À4 , 10 À5 , 10 À6 , and 10 À7 ) in PBS. Guinea pigs (4 groups of 6 animals each) were inoculated intradermally in the left rear foot with 0.1 mL of serially diluted viruses. According to the method described by Chen et al. [6] , the swine (4 groups of 4 each) were inoculated in the neck region by intramuscular injection of each animal with 2 mL of serially diluted virus. All of the animals were then monitored for the major clinical sign of FMD, the appearance of vesicles on the mouth or feet. The 50% animal infective dose (ID 50 ) was estimated using the Reed-Muench method [38] . Statistical analysis was performed with a log rank test 2 .