title: 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. 106-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.
  
  
  
  In 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.
authors: KU Leuven, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Leuven, Belgium.
authors: Elisa
authors: E
authors: Gayán
authors: KU Leuven, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Leuven, Belgium.
authors: Alexander
authors: A
authors: Cambré
authors: KU Leuven, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Leuven, Belgium.
authors: Chris W
authors: CW
authors: Michiels
authors: KU Leuven, Laboratory of Food Microbiology and Leuven Food Science and Nutrition Research Centre (LFoRCe), Department of Microbial and Molecular Systems (MS), Faculty of Bioscience Engineering, Leuven, Belgium abram.aertsen@biw.kuleuven.be.
authors: Abram
authors: A
authors: Aertsen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D015169:Colony Count, Microbial; D019020:Directed Molecular Evolution; D019453:Escherichia coli O157 / Q000235:genetics / Q000254:growth & development* / Q000472:pathogenicity; D057140:Fast Foods / Q000382:microbiology; D005511:Food Handling; D005516:Food Microbiology; D005519:Food Preservation; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018869:Heat-Shock Response; D006358:Hot Temperature; D006801:Humans; D006874:Hydrostatic Pressure; D009154:Mutation; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D006360:Heat-Shock Proteins; D012808:Sigma Factor; C069774:heat-shock sigma factor 32; C069567:sigma factor KatF protein, Bacteria