DEVELOPMENT OF A MICROTITER - BASED ASSAY FOR ASSESSMENT OF VIRULENCE RESPONSE IN SALMONELLA TYPHIMURIUM EXPOSED TO FRESH PRODUCE EXTRACTS

Abstract

Abstract The purpose of this research was to develop a microtiter-based assay procedure for assessment of virulence gene response of Salmonella Typhimurium to fresh homogenized vegetables. The microtiter procedure was adapted from a assay for β-galactosidase activity of a hilA fusion strain of S. Typhimurium with volumes of all reagents adjusted for microtiter plate wells. S. Typhimurium exposed to pH 7 saline yielded a higher level of hilA expression than responses after incubation in pH 4, 5 and 6 saline. Bacterial cells exposed to broccoli extracts yielded the higher levels of hilA expression while bell pepper and tomato yielded the overall lowest amounts of hilA expression. From this study, it appears that fresh produce extracts have different abilities to significantly alter virulence response in Salmonella. In conclusion, the hilA fusion stain assay can be successfully adapted to microtiter plates for testing Salmonella virulence response to vegetable extracts.