Influence of the rpoS gene and pre-adaptation in seawater on the tolerance to heavy metals of Salmonella enterica serovar Typhimurium

Abstract

Salmonella is an international food-borne pathogen disseminated widely in seawater that regularly causes large outbreaks of food poisoning. In this study, we investigated the effect of starvation on the survival ability of Salmonella enterica serovar Typhimurium rpoS+ and its mutant rpoS- after a 6-month incubation in seawater microcosms using a colorimetric XTT assay and colony forming units (CFU). The effect of pre-adaptation in seawater and the rpoS gene on the tolerance to heavy metals of this microorganism was also investigated. Our results showed that the number of cells decreased by ∼5 log units for the strain rpoS+ and by ∼5.5 log units for the mutant rpoS- after this period of stress. At the end of the experiments, cell viability was around of 20% and 10% for the wild type and mutant, respectively. We also revealed that the minimal inhibitory concentration values and cell viability under zinc, cobalt, mercury, chromium and cadmium heavymetals were decreased for the two starved strains. © 2012 Springer-Verlag and the University of Milan.