Survivability of Salmonella and Shigella spp. in sodium lauryl sulfate and tween 80 at 22 and 40°C

Abstract

Fresh produce has been implicated in several foodborne disease outbreaks. A primary site of contamination during production and handling is the surface of produce. One approach to reducing contamination is to treat fresh produce with rinsing agents. Studies have examined the efficacies of detergents and other rinses in recovering pathogens from produce surfaces. The determination of how these detergents affect bacterial cells may aid in understanding the mechanisms behind their removal. This study examines the survivability of Salmonella and Shigella in two detergents. A 0.1% sodium lauryl sulfate (SLS) solution, a 0.1% Tween 80 solution, and water were inoculated with a cocktail of stationary-phase organisms (3 log CPU/ml) and incubated for up to 32 h at 22°C and 40°C. Samples were taken over time and plated on tryptic soy agar supplemented with 50 ppm of nalidixic acid. Salmonella survived in all solutions and exhibited significant growth in water (0.8 log CFU/ml at 22°C and 1.9 log CFU/ml at 40°C) and Tween 80 (1.0 log CFU/ml at 40°C). Shigella survived in all solutions at 22°C and exhibited a growth level of 2.0 log CFU/ml in SLS. Shigella also survived in all solutions at 40°C, although its populations decreased significantly in Tween 80 over time. Elevated temperatures may allow Tween 80 to kill Shigella spp. over time. Overall, the detergents tested were not detrimental to the cells; therefore, if these solutions were to be used as produce rinse agents, they would aid in removal of organisms from surfaces rather than kill the cells.