Severely Heat Injured Survivors of E. coli O157:H7 ATCC 43888 Display Variable and Heterogeneous Stress Resistance Behavior

Quality changes in high hydrostatic pressure treated enriched tomato sauce

BACKGROUND

Use of high hydrostatic pressure (HHP) with reduced processing times is gaining traction in the food industry as an alternative to conventional thermal treatment. In order to enhance functional benefits while minimizing processing losses, functionalized products are being developed with such novel techniques. In this study, changes in quality parameters for HHP treated enriched tomato sauce were evaluated, with the aim to assess its viability as an alternative to conventional thermal treatment methods.

RESULTS

HHP treatments at 500 MPa, 30 °C/50 °C significantly increased the total phenolic and lycopene content of the sauce samples, achieving 6.7% and 7.5% improvements over conventionally treated samples. The antioxidant capacity of the HHP-treated samples was also found to match or be better than conventionally treated samples. Furthermore, a T2 relaxation time study revealed that pressure-temperature processing treatments were effective in maintaining the structural integrity of water molecules. Microbiological analyses revealed that 500 MPa/50 °C 5 min treatment can offer 8 logs reduction colony formation, matching the results of conventional thermal treatment.

CONCLUSION

Combined pressure-temperature treatments improve results, reduce time consumption. 500 MPa/50 °C treatments provided retention of quality parameters and significant reduction in microbial activity. © 2024 The Author(s). Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Evolutionary Processes Transpiring in the Stages of Lithopanspermia

Lithopanspermia is a theory proposing a natural exchange of organisms between solar system bodies as a result of asteroidal or cometary impactors. Research has examined not only the physics of the stages themselves but also the survival probabilities for life in each stage. However, although life is the primary factor of interest in lithopanspermia, this life is mainly treated as a passive cargo. Life, however, does not merely passively receive an onslaught of stress from surroundings; instead, it reacts. Thus, planetary ejection, interplanetary transport, and planetary entry are only the first three factors in the equation. The other factors are the quality, quantity, and evolutionary strategy of the transported organisms. Thus, a reduction in organism quantity in stage 1 might increase organism quality towards a second stress challenge in stage 3. Thus, robustness towards a stressor might in fact be higher in the bacterial population surviving after transport in stage 3 than at the beginning in stage 1. Therefore, the stages of lithopanspermia can themselves facilitate evolutionary processes that enhance the ability of the collected organisms to survive stresses such as pressure and heat shock. Thus, the multiple abiotic pressures that the population encounters through the three stages can potentially lead to very robust bacteria with survival capacities considerably higher than might otherwise be expected. This analysis details an outcome that is possible but probably rare. However, in addition to lithopanspermia, spacecraft mediated panspermia may also exist. The analogous stages in a spacecraft would result in a greater likelihood of increasing the stress tolerance of hitchhiking organisms. Furthermore, missions seeking life elsewhere will frequently be sent to places where the possibility of life as we know it is assumed to exist. Thus, we not only can transport terrestrial organisms to places where they are potentially more likely to survive but also may increase their invasive potential along the way. This analysis highlights further requirements that planetary protection protocols must implement and also provides a framework for analyses of ecological scenarios regarding the transmission of life, natural or artificial, between worlds in a solar system.

A trampoline effect occurring in the stages of planetary reseeding

Impactors have hit the Earth since its formation and have continued to be infrequent guests throughout the Earth's history. Although the early part of the Earth's history was marked by these violent events, life was present early, possibly existing already in the Hadean Eon. It is possible that life has been, and still is, transported between the worlds of the solar system, owing to impacts leading material away from the impact region. Beyond this lithopanspermia hypothesis, in the so-called 'refugium hypothesis', ejected material has been suggested to also return to its home planet and 'reseed' life after the world has recovered after a global impactor, thus restarting evolution. In addition to such impactors, more frequent impacts from smaller non-sterilizing impactors existed during the Heavy Bombardment epoch, feeding material potentially harbouring viable organisms into near Earth space. During the three stages of planetary self-reseeding, the encapsulated microbial population experiences abiotic stressors; specifically, they experience pressure and heat shock twice, in stage 1 and after a recovery phase in stage 2, and again in stage 3. Although many circumstances have played a role in the endurance of life in the early history of the Earth, a particular biological effect could potentially be conferred on a microbial population in this scenario. Thus, the surviving population not only would experience an increase in the frequency of robust genotypes but also would be expected to have greater stress tolerance than non-stressed organisms of the same species. Hence, because of the trampoline effect, the mean robustness of the microbial population towards these stressors is higher in stage 3 than stage 1. In principle, the time between the impactor and the reimpactor need not be long before this trampoline effect appears. Experiments simulating stage 1 must take this effect into consideration in estimating the survival probabilities of a population of organisms in worlds such as the past Earth. Thus, the stages of planetary self-reseeding can themselves be considered facilitators of a process that enhances the stress capacity of the collected microbial organisms and thus their survival capacity. This process may have played a role in the survival of life through violent periods of Earth's history and thus may affect inhabited worlds in general.

Role of Toxin-Antitoxin-Regulated Persister Population and Indole in Bacterial Heat Tolerance

YafQ is an endoribonuclease toxin that degrades target gene transcripts such as that of tnaA, a gene encoding tryptophanase to synthesize indole from tryptophan. DinJ is the cognate antitoxin of YafQ, and the YafQ-DinJ system was reported to regulate persister formation by controlling indole production in Escherichia coli In this study, we investigated the role of YafQ-DinJ, indole production, and persister population in bacterial heat tolerance. yafQ (ΔyafQ), dinJ (ΔdinJ), and tnaA (ΔtnaA) single-gene knockout mutants showed approximately 10-fold higher heat tolerance than wild-type (WT) E. coli BW25113. Persister fractions of all mutants were slightly larger than that of the WT. Interestingly, these persister cells showed an approximately 100-fold higher heat tolerance than normal cells, but there was no difference among the persister cells of all mutants and the WT in terms of heat tolerance. Indole and its derivatives promoted a drastic reduction of bacterial heat tolerance by just 10 min of pretreatment, which is not sufficient to affect persister formation before heat treatment. Surprisingly, indole and its derivatives also reduced the heat tolerance of persister cells. Among the tested derivatives, 5-iodoindole exhibited the strongest effect on both normal and persister cells.IMPORTANCE Our study demonstrated that a small persister population exhibits significantly higher heat tolerance than normal cells and that this small fraction contributes to the heat tolerance of the total bacterial population. This study also demonstrated that indole, known to inhibit persister formation, and its derivatives are very promising candidates to reduce the heat tolerance of not only normal bacterial cells but also persister cells.

Combination of mild heat and plant essential oil constituents to inactivate resistant variants of Escherichia coli in buffer and in coconut water

The growing demand for minimally processed foods with clean labels has stimulated research into mild processing methods and natural antimicrobials to replace intensive heating and conventional preservatives, respectively. However, we have previously demonstrated that repetitive exposure of some bacteria to mild heat or subinhibitory concentrations of essential oil constituents (EOCs) may induce the emergence of mutants with increased resistance to these treatments. Since the combination of mild heat with some EOCs has a synergistic effect on microbial inactivation, we evaluated the potential of such combinations against our resistant E. coli mutants. While citral, carvacrol and t-cinnamaldehyde synergistically increased heat inactivation (53.0 °C, 10 min) of the wild-type MG1655 suspended in buffer, only the combination with carvacrol (200 μl/l) was able to mitigate the increased resistance of all the mutants. Moreover, the combination of heat and carvacrol acted synergistically inactivating heat-resistant variants of E. coli O157:H7 (ATCC 43888). This combined treatment could synergistically achieve more than 5 log₁₀ reductions of the most resistant mutants in coconut water, although the temperature had to be raised to 57.0 °C. Therefore, the combination of mild heat with carvacrol appears to hold promise for mild processing, and it is expected to counteract the development of heat resistance.

A Novel Aqueous Ozone Treatment as a Spray Chill Intervention against Escherichia coli O157:H7 on Surfaces of Fresh Beef

This experiment determined the efficacy of using a novel aqueous ozone treatment as a spray chill intervention to reduce Escherichia coli O157:H7 on surfaces of fresh beef compared with traditional water spray chill. Cutaneous trunci muscles were obtained from a local beef cattle processing plant. Muscles were divided into sixteen 25-cm² sections, and each section was individually inoculated with E. coli O157:H7 to the final concentration of approximately 10⁵ CFU/cm². Muscle sections were collected and tested before and after simulated spray chill treatments of water or the novel aqueous ozone solution. Enumeration of survivors of each treatment was compared with that of the untreated muscle sections. Water spray chill reduced (P ≤ 0.05) E. coli O157:H7 0.60 log, whereas the aqueous ozone spray chill reduction (P ≤ 0.05) was 1.46 log on surfaces of fresh beef. Aqueous ozone spray chill reduced (P ≤ 0.05) aerobic bacteria 0.99 log, but water spray chill did not significantly (P > 0.05) reduce aerobic bacteria on surfaces of fresh beef. The findings indicate that aqueous ozone can be used as a spray chill intervention to enhance the safety of beef.

Indole at low concentration helps exponentially growing Escherichia coli survive at high temperature

A culture of stationary phase Escherichia coli cells has been reported to produce copious indole when exposed to high temperature (50°C), and this response has been proposed to aid survival. We reinvestigated this phenomenon and found that indole production under these conditions is probably not a direct response to heat stress. Rather, E. coli produces indole when growth is prevented, irrespective of whether this is due to heat stress, antibiotic treatment or the removal of nutrients. Moreover, 300μM indole produced at 50°C does not improve the viability of heat stressed cells. Interestingly, a much lower concentration of indole (20 μM) improves the survival of an indole-negative strain (ΔtnaA) when heat stressed during exponential growth. In addition we have shown that the distribution of tryptophanase, the enzyme responsible for indole synthesis, is highly heterogeneous among cells in a population, except during the transition between exponential and stationary phases. The observation that, despite the presence of the tryptophanase, very little indole is produced during early exponential phase suggests that there is post-translational regulation of the enzyme.

Virulence and transcriptome profile of multidrug-resistant Escherichia coli from chicken

Numerous studies have examined the prevalence of pathogenic Escherichia coli in poultry and poultry products; however, limited data are available regarding their resistance- and virulence-associated gene expression profiles. This study was designed to examine the resistance and virulence of poultry E. coli strains in vitro and in vivo via antibiotic susceptibility, biofilm formation and adhesion, and invasion and intracellular survivability assays in Caco-2 and Raw 264.7 cell lines as well as the determination of the median lethal dose in two-day old chickens. A clinical pathogenic multidrug-resistant isolate, E. coli 381, isolated from broilers, was found to be highly virulent in cell culture and 1000-fold more virulent in a chicken model than other strains; accordingly, the isolate was subsequently selected for transcriptome analysis. The comparative gene expression profile of MDR E. coli 381 and the reference human strain E. coli ATCC 25922 was completed with Illumina HiSeq. 2500 transcriptome analysis. Differential gene expression analysis indicates that there are multiple pathways involved in the resistance and virulence of this highly virulent strain. The results garnered from this study provide critical information about the highly virulent MDR E. coli strain of poultry origin and warrant further investigation due to its significant threat to public health.

Health and Safety Considerations of Fermented Sausages

Fermented sausages are highly treasured traditional foods. A large number of distinct sausages with different properties are produced using widely different recipes and manufacturing processes. Over the last years, eating fermented sausages has been associated with potential health hazards due to their high contents of saturated fats, high NaCl content, presence of nitrite and its degradation products such as nitrosamines, and use of smoking which can lead to formation of toxic compounds such as polycyclic aromatic hydrocarbons. Here we review the recent literature regarding possible health effects of the ingredients used in fermented sausages. We also go through attempts to improve the sausages by lowering the content of saturated fats by replacing them with unsaturated fats, reducing the NaCl concentration by partly replacing it with KCl, and the use of selected starter cultures with desirable properties. In addition, we review the food pathogenic microorganisms relevant for fermented sausages(Escherichia coli,Salmonella enterica,Staphylococcus aureus,Listeria monocytogenes,Clostridium botulinum, andToxoplasma gondii)and processing and postprocessing strategies to inhibit their growth and reduce their presence in the products.