Cell-cell interactions influence resistance and survival of Salmonella serotype Typhimurium to environmental stress

Abstract

Aims: The aim of this work was to study the effects of prolonged nutrient stress on survival, cell interactions and resistance to inimical processes in Salmonella serotype Typhimurium. Methods and Results: Salmonella Typhimurium cells were subjected to prolonged incubation in the stationary phase of growth and the properties of starved cells (old) were investigated with reference to those of exponentiallygrowing cells (young). Competition experiments between old and young cells revealed cell-cell interactions that influenced stationary phase survival and response of the bacterium to heat stress. During prolonged incubation of cells, cycles of resistance and sensitivity to heat stress were identified. Competition experiments between old and young cells revealed that the resistance of young cells to heat increased to levels more like those of stationary phase cells than growing cells. The presence of old cells influenced the phenotype of young cells, possibly by means of cell-cell interactions. There was no evidence for the involvement of any extracellularly-produced factors in this phenomenon, but a requirement that the old competitor cells be viable could be demonstrated. Conclusions: It is proposed that the complex interactions within stationary phase cultures of Salm. Typhimurium may be due to cycles of mutation in concert with an as yet undefined interaction between old cells and growing ones. Significance and Impact of the Study: This study provides evidence for active and diverse responses to nutrient stress within populations of Salm. Typhimurium that promote survival and that may be important for the success of this bacterium as a pathogen.

Número mais provável (NMP) de Salmonella sp. em cecos de frangos de corte e correlação com a população linfocitária bursal

“…No que se refere ao isolamento de salmonelas a partir de cecos, alguns fatores podem interferir nos resultados, como sorovares que apresentam uma fase estacionária adaptativa, mostrando menor crescimento celular e aumentando a termotolerância quando na presença de bactérias competidoras [10,26]. Os microrganismos mantidos em temperaturas de congelamento ou mesmo temperaturas inferiores à sua faixa ótima de crescimento poderiam ser considerados dormentes e, conseqüentemente, não teriam atividade metabólica aparente [22].…”