Resistance changes in Salmonella enterica serovar Typhimurium treated by High Hydrostatic Pressure and Pulsed Electric Fields and assessment of virulence changes by using Caenorhabditis elegans as a test organism

Abstract

The goal of this study was to evaluate the development of Salmonella enterica subsp. enterica serovar Typhimurium resistance against Pulsed Electric Fields (PEF) and High Hydrostatic Pressure (HHP), and to study the possible virulence changes of the resistant subpopulations using Caenorhabditis elegans. Results showed that S. Typhimurium became resistant to both non-thermal technologies after four consecutive treatments. Survival probability of the worms (C. elegans) increased significantly when they were fed with S. Typhimurium treated by PEF four consecutive times in comparison with the other two subpopulations, untreated and treated once. For HHP, results indicated that up to percentile 50%, the survival probability of worms fed with treated microorganisms (once and four times) was greater than that of worms fed with untreated ones. Also, the C. elegans egg-laying pattern was modified and there were significant differences in the number of eggs laid in the first two days among the three subpopulations studied. Consequently, although S. Typhimurium develops microbial resistance against PEF or HHP treatments, when it is applied repeatedly, its virulence against C. elegans appears to decrease.