Stress-Induced Evolution of Heat Resistance and Resuscitation Speed in Escherichia coli O157:H7 ATCC 43888

Abstract

The development of resistance in foodborne pathogens to food preservation techniques is an issue of increasing concern, especially in minimally processed foods where safety relies on hurdle technology. In this context, mild heat can be used in combination with so-called nonthermal processes, such as high hydrostatic pressure (HHP), at lower individual intensities to better retain the quality of the food. However, mild stresses may increase the risk of (cross-)resistance development in the surviving population, which in turn might compromise food safety. In this investigation, we examined the evolution of Escherichia coli O157:H7 strain ATCC 43888 after recurrent exposure to progressively intensifying mild heat shocks (from 54.0°C to 60.0°C in 0.5°C increments) with intermittent resuscitation and growth of survivors. As such, mutant strains were obtained after 10 cycles of selection with ca. 10 6 -fold higher heat resistance than that for the parental strain at 58.0°C, although this resistance did not extend to temperatures exceeding 60.0°C. Moreover, these mutant strains typically displayed cross-resistance against HHP shock and displayed signs of enhanced RpoS and RpoH activity. Interestingly, additional cycles of selection maintaining the intensity of the heat shock constant (58.5°C) selected for mutant strains in which resuscitation speed, rather than resistance, appeared to be increased. Therefore, it seems that resistance and resuscitation speed are rapidly evolvable traits in E. coli ATCC 43888 that can compromise food safety. IMPORTANCEIn this investigation, we demonstrated that Escherichia coli O157:H7 ATCC 43888 rapidly acquires resistance to mild heat exposure, with this resistance yielding cross-protection to high hydrostatic pressure treatment. In addition, mutants of E. coli ATCC 43888 in which resuscitation speed, rather than resistance, appeared to be improved were selected. As such, both resistance and resuscitation speed seem to be rapidly evolvable traits that can compromise the control of foodborne pathogens in minimal processing strategies, which rely on the efficacy of combined mild preservation stresses for food safety. Minimal processing of foods is based on the combination of mild preservation methods (or hurdles) for maximizing retention of the sensorial and nutritional properties of the food while maintaining the appropriate level of food safety and shelf life (1, 2). Methods such as mild heating, acidification, and the use of natural antimicrobial compounds, high hydrostatic pressure (HHP), pulsed electric fields, ultrasound, and irradiation are some of the techniques commonly used in hurdle approaches (2-4). While the efficacy of minimal processing relies on the additive, or even synergistic, lethal or growth-inhibitory effects of such mild hurdles, the mild intensity might nevertheless pose the risk of increasing resistance to the corresponding treatments. More specifically, rare mutant strains with an increased stress resistance that can spontaneously emerge in a population ...

Multi‐Channel Optical Device for Solar‐Driven Bacterial Inactivation under Real‐Time Temperature Feedback

“…of the Ti/ IrO 2 À CS/UCNP-CS device was calculated to be 58.5°C, the surrounding temperature increased to 50°C (Figure 3C), which was too high to develop heat resistance in bacteria. [19] Finite element analysis also illustrated that the device was heated evenly and therefore allowed precise determination of the temperature (Figure 3D). Therefore, accurate temperatures could be acquired by UCL emission spectra to monitor the temperature during the solar-driven photothermal process.…”

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

“…Escherichia coli O157:H7 exposed to progressively intensifying milder heat (54–60°C) treatment displayed higher resistance to high hydrostatic pressure possibly by activating RpoS and RpoH ( Gayán et al, 2016 ). Interestingly, in C. botulinum , exposure to prolonged heat stress (45°C), heat shock genes and members of the SOS regulons were activated while genes encoding neurotoxin ( botA ) synthesis was downregulated ( Selby et al, 2017 ).…”

Impact of high hydrostatic pressure on bacterial proteostasis

“…10,000-fold [91]. Furthermore, the large intrinsic variability in HHP resistance observed among natural enterohemorrhagic E. coli isolates has been related to variations in cellular RpoS activity [92][93], and the modulation of the RpoS response has proven to be an important evolutionary strategy in E. coli O157:H7 to improve stress tolerance [5,94]. Indeed, exposure of E. coli O157:H7 (ATCC 43888) to a limited number of progressively intensifying HHP shocks with intermittent resuscitation rapidly selected for HHP-resistant (and heat crossresistant) mutants that displayed clear signs of increased RpoS activity [5].…”