The Potential Link between Thermal Resistance and Virulence in Salmonella: A Review

Abstract

In some animals, the typical body temperature can be higher than humans, for example, 42°C in poultry and 40°C in rabbits which can be a potential thermal stress challenge for pathogens. Even in animals with lower body temperatures, when infection occurs, the immune system may increase body temperature to reduce the chance of survival for pathogens. However, some pathogens can still easily overcome higher body temperatures and/or rise in body temperatures through expression of stress response mechanisms. Salmonella is the causative agent of one of the most prevalent foodborne illnesses, salmonellosis, and can readily survive over a wide range of temperatures due to the efficient expression of the heat (thermal) stress response. Therefore, thermal resistance mechanisms can provide cross protection against other stresses including the non-specific host defenses found within the human body thus increasing pathogenic potential. Understanding the molecular mechanisms associated with thermal responses in Salmonella is crucial in designing and developing more effective or new treatments for reducing and eliminating infection caused by Salmonella that have survived heat stress. In this review, Salmonella thermal resistance is assessed followed by an overview of the thermal stress responses with a focus on gene regulation by sigma factors, heat shock proteins, along with the corresponding thermosensors and their association with virulence expression including a focus on a potential link between heat resistance and potential for infection.

Role of cAMP receptor protein in phenotype and stress tolerance in Salmonella enterica serovar Typhimurium

“…An earlier study indicates that the absence of CRP leads to an increase in the periplasmic protease HtrA [43]. HtrA is an important protein in higher thermotolerance in E. coli [43]. In this study, we observed a significant increase in the expression of htrA (Figure 4c).…”

“…Both the alternate sigma factors rpoE and rpoH, are involved in extreme heat stress response [43]. An earlier study indicates that the absence of CRP leads to an increase in the periplasmic protease HtrA [43]. HtrA is an important protein in higher thermotolerance in E. coli [43].…”

Comparative roles of clpA and clpB in the survival of S. Typhimurium under stress and virulence in poultry

“…The body temperature of poultry is 42 °C, hence S . Typhimurium experience constant thermal stress inside birds 46 . Therefore, the contributions of clpA and clpB genes in the in vitro survival of S .…”

Food-Associated Stress Primes Foodborne Pathogens for the Gastrointestinal Phase of Infection

“…Advanced food processing and preservation techniques are designed to reduce pathogen or toxin load or eliminate them from food; however, studies have suggested that food preservation techniques could create a sub-lethal environment ( Capozzi et al, 2009 ). It is widely accepted that the sub-lethal treatments may trigger a bacterial stress response that results in changes in gene expression, leading to not only enhanced bacterial resistance to antimicrobials or preservation conditions but also enhanced pathogen survivability and virulence ( Wesche et al, 2009 ; Spector and Kenyon, 2012 ; Verraes et al, 2013 ; Sun, 2014 ; NicAogáin and O’Byrne, 2016 ; Dawoud et al, 2017 ; Esbelin et al, 2018 ). Similarly, to overcome pathogenic microbial assault, a series of host defenses is strategically placed throughout the orogastric and intestinal tract ( Fang et al, 2016 ).…”