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1
Lin, Tao, Bingwei Hou, Zhe Wang und Wei Chen. „Inactivation of particle-associated Escherichia coli with chlorine dioxide“. Water Supply 17, Nr. 1 (26.07.2016): 151–60. http://dx.doi.org/10.2166/ws.2016.121.
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In this paper, the inactivation of both free Escherichia coli (FE) and particle-associated E. coli (PAE) with chlorine dioxide (ClO2) were investigated using granular activated carbon effluent water samples. The inactivation rate of FE was higher than that of PAE and the reactivation ratio of PAE was higher than that of FE, indicating the threat of particle-associated bacteria. Response surface methodology (RSM) was applied to determine the factors influencing the disinfection efficiency of ClO2 in inactivating PAE. The experimental results indicated that particle concentration was a principal factor influencing the PAE inactivation efficiency, presenting a negative correlation, while exposure time and ClO2 dosage revealed a positive correlation. The inactivation kinetics of PAE using ClO2 was also investigated and the results demonstrated that PAE inactivation with ClO2 fitted the Chick–Watson kinetic model. The inactivation rate constants of PAE were found to follow the Arrhenius expression with an activation energy of 107.5 kJ/mol, indicating a relatively strong temperature dependence. However, there are minor effects of pH and initial ClO2 dosage on PAE inactivation rate constant.
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BLACK, D. GLENN, FEDERICO HARTE und P. MICHAEL DAVIDSON. „Escherichia coli Thermal Inactivation Relative to Physiological State“. Journal of Food Protection 72, Nr. 2 (01.02.2009): 399–402. http://dx.doi.org/10.4315/0362-028x-72.2.399.
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Studies have explored the use of various nonlinear regression techniques to better describe shoulder and/or tailing effects in survivor curves. Researchers have compiled and developed a number of diverse models for describing microbial inactivation and presented goodness of fit analysis to compare them. However, varying physiological states of microorganisms could affect the measured response in a particular population and add uncertainty to results from predictive models. The objective of this study was to determine if the shape and magnitude of the survivor curve are possibly the result of the physiological state, relative to growth conditions, of microbial cells at the time of heat exposure. Inactivation tests were performed using Escherichia coli strain K-12 in triplicate for three growth conditions: statically grown cells, chemostat-grown cells, and chemostat-grown cells with buffered (pH 6.5) feed media. Chemostat cells were significantly less heat resistant than the static or buffered chemostat cells at 58°C. Regression analysis was performed using the GInaFiT freeware tool for Microsoft Excel. A nonlinear Weibull model, capable of fitting tailing effects, was effective for describing both the static and buffered chemostat cells. The log-linear response best described inactivation of the nonbuffered chemostat cells. Results showed differences in the inactivation response of microbial cells depending on their physiological state. The use of any model should take into consideration the proper use of regression tools for accuracy and include a comprehensive understanding of the growth and inactivation conditions used to generate thermal inactivation data.
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WANG, ZUWEN, XIUFANG BI, RUI XIANG, LIYI CHEN, XIAOPING FENG, MIN ZHOU und ZHENMING CHE. „Inactivation of Escherichia coli by Ultrasound Combined with Nisin“. Journal of Food Protection 81, Nr. 6 (14.05.2018): 993–1000. http://dx.doi.org/10.4315/0362-028x.jfp-18-023.
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ABSTRACT The aim of this study was to investigate the inactivation of nonpathogenic Escherichia coli in nutrient broth and milk through the use of either ultrasound (US) alone or US combined with nisin (US + nisin) treatments. The E. coli cells were treated at 0 to 55°C, 242.04 to 968.16 W/cm2 for 0 to 15 min. The results showed that the inactivation of E. coli by US and US + nisin increased when the temperature, US power density, and treatment time were increased. The inactivation kinetics of E. coli in nutrient broth by US and US + nisin both conformed to linear models. The largest reductions of 2.89 and 2.93 log cycles by US and US + nisin, respectively, were achieved at 968.16 W/cm2 and at 25°C for 15 min. The suspension media of the E. coli cells influenced the inactivation effect of US, while the growth phases of E. coli cells did not affect their resistance to US. Under all experiment conditions of this study, the differences between US and US + nisin in their respective inactivation effects on E. coli were not obvious. The results suggested that nisin had either no effect at all or a weak synergistic effect with US and that the E. coli cells were inactivated mainly by US, thus indicating that the inactivation of E. coli by US is an “all or nothing” event.
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SAUER, ANNE, und CARMEN I. MORARU. „Inactivation of Escherichia coli ATCC 25922 and Escherichia coli O157:H7 in Apple Juice and Apple Cider, Using Pulsed Light Treatment“. Journal of Food Protection 72, Nr. 5 (01.05.2009): 937–44. http://dx.doi.org/10.4315/0362-028x-72.5.937.
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The main objective of this work was to evaluate the effectiveness of pulsed light (PL) treatment for the inactivation of Escherichia coli in liquids with different levels of clarity. Nonpathogenic E. coli ATCC 25922 and pathogenic E. coli O157: H7 were used as challenge organisms. Butterfield's phosphate buffer (BPB), tryptic soy broth (TSB), apple juice, and apple cider were used as substrates. The inoculated liquids were placed in a thin layer (1.3 mm) into glass chambers (23 by 53 by 11 mm) and exposed to PL doses of up to 13.1 J/cm2. PL treatments were performed in a Xenon RS-3000C PL unit, both in static mode and under turbulence. Survivors were determined by standard plate counting or the most-probable-number technique. For static treatments, reduction levels exceeding 8.5 log were obtained in BPB for all strains and reduction levels of about 3.5 log were obtained in TSB. For apple juice, inactivation levels of 2.66 ± 0.10 log were obtained for E. coli ATCC 25922 and 2.52 ± 0.19 log for E. coli O157:H7. In cider, inactivation levels of 2.32 ± 0.16 log and 3.22 ± 0.29 log were obtained for the nonpathogenic and pathogenic strains, respectively. Inactivation kinetics was characterized using the Weibull model. Turbulent treatments resulted in 5.76 ± 0.06 log reduction in cider and 7.15 ± 0.22 log reduction in juice, which satisfies the U.S. Food and Drug Administration requirement of 5-log reduction of E. coli. These results show promise for the use of PL for the effective reduction of E. coli in apple juice and cider.
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QUINTERO-RAMOS, A., J. J. CHUREY, P. HARTMAN, J. BARNARD und R. W. WOROBO. „Modeling of Escherichia coli Inactivation by UV Irradiation at Different pH Values in Apple Cider“. Journal of Food Protection 67, Nr. 6 (01.06.2004): 1153–56. http://dx.doi.org/10.4315/0362-028x-67.6.1153.
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This study examined the effects and interactions of UV light dose (1,800 to 20,331 μJ/cm2) and apple cider pH (2.99 to 4.41) on the inactivation of Escherichia coli ATCC 25922, a surrogate for E. coli O157:H7. A predictive model was developed to relate the log reduction factor of E. coli ATCC 25922 to the UV dose. Bacterial populations for treated and untreated samples were enumerated with the use of nonselective media. The results revealed that UV dose was highly significant in the inactivation of E. coli, whereas pH showed no significant effect at higher UV doses. Doses of 6,500 μJ/cm2 or more were sufficient to achieve a greater than 5-log reduction of E. coli. Experimental inactivation data were fitted adequately by a logistic regression model. UV irradiation is an attractive alternative to conventional methods for reducing bacteria in unpasteurized apple cider.
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Jocic, Miodrag, Miroljub Trkuljic, Dragana Jovicic, Nemanja Borovcanin, Milena Todorovic und Bela Balint. „Mirasol PRT system inactivation efficacy evaluated in platelet concentrates by bacteria-contamination model“. Vojnosanitetski pregled 68, Nr. 12 (2011): 1041–46. http://dx.doi.org/10.2298/vsp1112041j.
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Background/Aim. Bacterial contamination of blood components, primarily platelet concentrates (PCs), has been identified as one of the most frequent infectious complications in transfusion practice. PC units have a high risk for bacterial growth/multiplication due to their storage at ambient temperature (20 ? 2?C). Consequences of blood contamination could be effectively prevented or reduced by pathogen inactivation systems. The aim of this study was to determine the Mirasol pathogen reduction technology (PRT) system efficacy in PCs using an artificial bacteria-contamination model. Methods. According to the ABO blood groups, PC units (n = 216) were pooled into 54 pools (PC-Ps). PC-Ps were divided into three equal groups, with 18 units in each, designed for an artificial bacteria-contamination. Briefly, PC-Ps were contaminated by Staphylococcus epidermidis, Staphylococcus aureus or Escherichia coli in concentrations 102 to 107 colony forming units (CFU) per unit. Afterward, PC-Ps were underwent to inactivation by Mirasol PRT system, using UV (l = 265-370 nm) activated riboflavin (RB). All PC-Ps were assayed by BacT/Alert Microbial Detection System for CFU quantification before and after the Mirasol treatment. Samples from non-inactivated PC-P units were tested after preparation and immediately following bacterial contamination. Samples from Mirasol treated units were quantified for CFUs one hour, 3 days and 5 days after inactivation. Results. A complete inactivation of all bacteria species was obtained at CFU concentrations of 102 and 103 per PC-P unit through storage/ investigation period. The most effective inactivation (105 CFU per PC-P unit) was obtained in Escherichia coli setting. Contrary, inactivation of all the three tested bacteria species was unworkable in concentrations of ? 106 CFU per PC-P unit. Conclusion. Efficient inactivation of investigated bacteria types with a significant CFU depletion in PC-P units was obtained - 3 Log for all three tested species, and 5 Log for Escherichia coli. The safety of blood component therapy, primarily the clinical use of PCs can be improved using the Mirasol PRT system.
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Moxley, Rodney A., Emil M. Berberov, David H. Francis, Jun Xing, Mahtab Moayeri, Rodney A. Welch, Diane R. Baker und Raúl G. Barletta. „Pathogenicity of an EnterotoxigenicEscherichia coli Hemolysin (hlyA) Mutant in Gnotobiotic Piglets“. Infection and Immunity 66, Nr. 10 (01.10.1998): 5031–35. http://dx.doi.org/10.1128/iai.66.10.5031-5035.1998.
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ABSTRACT Pigs infected with hemolytic F4+ strains of enterotoxigenic Escherichia coli often develop septicemia secondary to intestinal infection. We tested the hypothesis that inactivation of hemolysin would reduce the ability of F4+enterotoxigenic E. coli to cause septicemia in swine following oral inoculation. Inactivation of the hemolysin structural gene (hlyA) did not decrease the incidence of septicemia in the gnotobiotic piglet model.
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McQuestin, Olivia J., Craig T. Shadbolt und Tom Ross. „Quantification of the Relative Effects of Temperature, pH, and Water Activity on Inactivation of Escherichia coli in Fermented Meat by Meta-Analysis“. Applied and Environmental Microbiology 75, Nr. 22 (18.09.2009): 6963–72. http://dx.doi.org/10.1128/aem.00291-09.
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ABSTRACT Outbreaks of Escherichia coli infections linked to fermented meats have prompted much research into the kinetics of E. coli inactivation during fermented meat manufacture. A meta-analysis of data from 44 independent studies was undertaken that allowed the relative influences of pH, water activity (aw), and temperature on E. coli survival during fermented meat processing to be investigated. Data were reevaluated to determine rates of inactivation, providing 484 rate data points with various pH (2.8 to 6.14), aw (0.75 to 0.986), and temperature (−20 to 66�C) values, product formulations, and E. coli strains and serotypes. When the data were presented as an Arrhenius model, temperature (0 to 47�C) accounted for 61% of the variance in the ln(inactivation rate) data. In contrast, the pH or aw measured accounted for less than 8% of variability in the data, and the effects of other pH- and aw-based variables (i.e., total decrease and rates of reduction of those factors) were largely dependent on the temperature of the process. These findings indicate that although temperatures typically used in fermented meat manufacture are not lethal to E. coli per se, when other factors prevent E. coli growth (e.g., low pH and aw), the rate of inactivation of E. coli is dominated by temperature. In contrast, inactivation rates at temperatures above ∼50�C were characterized by smaller z values than those at 0 to 47�C, suggesting that the mechanisms of inactivation are different in these temperature ranges. The Arrhenius model developed can be used to improve product safety by quantifying the effects of changes in temperature and/or time on E. coli inactivation during fermented meat manufacture.
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HARTE, FEDERICO, GLENN BLACK und P. MICHAEL DAVIDSON. „Theil Error Splitting Method for Selecting the “Best Model” in Microbial Inactivation Studies“. Journal of Food Protection 72, Nr. 4 (01.04.2009): 843–48. http://dx.doi.org/10.4315/0362-028x-72.4.843.
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Escherichia coli K-12 was grown under unbuffered, buffered, and starving environmental conditions and then subjected to isothermal inactivation at 58°C for up to 30 min. Survival versus time data were used to evaluate three models reported as suitable for the prediction of microbial inactivation by thermal means. The error splitting method proposed by Theil was used to divide the average squared difference between each observed and predicted datum into three orthogonal error sources: bias, regression, and random error. The method is based on the hypothesis that if the model is accurate, the overall average predicted and observed values should be the same and a plot of observed versus predicted inactivation values should have a slope of 1. The bias fixed error term quantifies the overall average difference between predicted and observed inactivation values. The regression fixed error term quantifies the difference between observed and predicted values near the end of the predictive region, where shoulders and tails may occur. The random error term quantifies the random variability of the predicted versus observed inactivation values. Statistical tests were proposed to determine the significance of each fixed error term and the normality of the random error source. The method was used to discuss the goodness of fit for the three models for Escherichia coli. The best model was the one that minimized total residual error, maximized random error sources (i.e., fixed error terms are not significant), and maximized the coefficient of correlation between observed and predicted inactivation values.
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HUANG, LIHAN, und VIJAY K. JUNEJA. „A New Kinetic Model for Thermal Inactivation of Microorganisms: Development and Validation Using Escherichia coli O157:H7 as a Test Organism†“. Journal of Food Protection 64, Nr. 12 (01.12.2001): 2078–82. http://dx.doi.org/10.4315/0362-028x-64.12.2078.
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A new kinetic model has been proposed to simulate the nonlinear behavior of survivor curves frequently observed in thermal inactivation of microorganisms. This model incorporates a time component into the first-order inactivation kinetics and is capable of describing the linear, convex, and concave survivor curves. The model was validated using Escherichia coli O157:H7 as a test microorganism. Ground beef (93% lean) samples inoculated to 107 to 108 CFU/g of meat were subjected to immersion heating at 55, 57.5, 60, 62.5, and 65°C, respectively, in a water bath. All the survivor curves in this study showed upward concavity. Linear and nonlinear regressions were used to fit the survivor curves to the linear first-order inactivation kinetics and the proposed model. Analyses showed that the new kinetic model provides a much better estimate of the thermal inactivation behavior of E. coli O157:H7 in ground beef.
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Koottatep, T., S. Phuphisith, T. Pussayanavin, A. Panuvatvanich und C. Polprasert. „Modeling of pathogen inactivation in thermal septic tanks“. Journal of Water, Sanitation and Hygiene for Development 4, Nr. 1 (13.12.2013): 81–88. http://dx.doi.org/10.2166/washdev.2013.190.
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Thermal application has been widely used for pathogen inactivation in various fields. The purpose of this research was to develop a model of pathogen inactivation in septic tanks operating at various temperatures. Four laboratory-scale septic tanks fed with septage were operated at temperatures of 30, 40, 50 and 60 °C and Escherichia coli (E. coli) was selected as the pathogenic indicator. The efficiencies of E. coli inactivation were found to increase with increasing temperatures, while the opposites were observed for chemical oxygen demand (COD) reduction. At 60 °C, the E. coli concentrations were reduced from 9.6 × 106 to about 10 most probable number (MPN)/100 mL or 6 log reduction. The kinetics of E. coli reduction followed a modified Weibull model which could be applied to septic tank design and operation. The percentage COD removal was found to be 93, 94, 89 and 84 at temperatures of 32, 40, 50 and 60 °C, respectively. The results of this study suggested that pathogenic microorganisms in septic tanks could be inactivated to be at a safe level with thermal application.
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SUEHR, QUINCY J., NATHAN M. ANDERSON und SUSANNE E. KELLER. „Desiccation and Thermal Resistance of Escherichia coli O121 in Wheat Flour“. Journal of Food Protection 82, Nr. 8 (16.07.2019): 1308–13. http://dx.doi.org/10.4315/0362-028x.jfp-18-544.
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ABSTRACT Non-O157 Shiga toxin–producing Escherichia coli infections have recently been associated with wheat flour on two separate accounts in the United States and Canada. However, there is little information regarding the thermal resistance and longevity of non-O157 Shiga toxin–producing Escherichia coli during storage in low-moisture environments. The objectives of this study were to determine the thermal inactivation kinetics of E. coli O121 in wheat flour and to compare the thermal inactivation rates with those of other pathogens. Wheat flour, inoculated with E. coli O121, was equilibrated at 25°C to a water activity of 0.45 in a humidity-controlled conditioning chamber. Inoculated samples were treated isothermally at 70, 75, and 80°C, and posttreatment population survivor ratios were determined by plate counting. D- and z-values calculated with a log-linear model, were compared with those obtained in other studies. At 70, 75, and 80°C, the D-values for E. coli O121 were 18.16 ± 0.96, 6.47 ± 0.50, and 4.58 ± 0.40 min, respectively, and the z-value was 14.57 ± 2.21°C. Overall, E. coli O121 was observed to be slightly less thermally resistant than what has been previously reported for Salmonella Enteritidis PT30 in wheat flour as measured under the same conditions with the same methods.
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Cook, William R., und Lawrence I. Rothfield. „Nucleoid-Independent Identification of Cell Division Sites in Escherichia coli“. Journal of Bacteriology 181, Nr. 6 (15.03.1999): 1900–1905. http://dx.doi.org/10.1128/jb.181.6.1900-1905.1999.
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ABSTRACT The mechanism used by Escherichia coli to determine the correct site for cell division is unknown. In this report, we have attempted to distinguish between a model in which septal position is determined by the position of the nucleoids and a model in which septal position is predetermined by a mechanism that does not involve nucleoid position. To do this, filaments with extended nucleoid-free regions adjacent to the cell poles were produced by simultaneous inactivation of cell division and DNA replication. The positions of septa that formed within the nucleoid-free zones after division was allowed to resume were then analyzed. The results showed that septa were formed at a uniform distance from cell poles when division was restored, with no relation to the distance from the nearest nucleoid. In some cells, septa were formed directly over nucleoids. These results are inconsistent with models that invoke nucleoid positioning as the mechanism for determining the site of division site formation.
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Qian, Jueying, Evelyn Walters, Peter Rutschmann, Michael Wagner und Harald Horn. „Modelling the influence of total suspended solids on E. coli removal in river water“. Water Science and Technology 73, Nr. 6 (07.12.2015): 1320–32. http://dx.doi.org/10.2166/wst.2015.605.
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Following sewer overflows, fecal indicator bacteria enter surface waters and may experience different lysis or growth processes. A 1D mathematical model was developed to predict total suspended solids (TSS) and Escherichia coli concentrations based on field measurements in a large-scale flume system simulating a combined sewer overflow. The removal mechanisms of natural inactivation, UV inactivation, and sedimentation were modelled. For the sedimentation process, one, two or three particle size classes were incorporated separately into the model. Moreover, the UV sensitivity coefficient α and natural inactivation coefficient kd were both formulated as functions of TSS concentration. It was observed that the E. coli removal was predicted more accurately by incorporating two particle size classes. However, addition of a third particle size class only improved the model slightly. When α and kd were allowed to vary with the TSS concentration, the model was able to predict E. coli fate and transport at different TSS concentrations accurately and flexibly. A sensitivity analysis revealed that the mechanisms of UV and natural inactivation were more influential at low TSS concentrations, whereas the sedimentation process became more important at elevated TSS concentrations.
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Setikaite, Ilona, Tatiana Koutchma, Eduardo Patazca und Brian Parisi. „Effects of Water Activity in Model Systems on High-Pressure Inactivation of Escherichia coli“. Food and Bioprocess Technology 2, Nr. 2 (28.02.2008): 213–21. http://dx.doi.org/10.1007/s11947-008-0069-7.
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Cho, Min, Yunho Lee, Hyenmi Chung und Jeyong Yoon. „Inactivation of Escherichia coli by Photochemical Reaction of Ferrioxalate at Slightly Acidic and Near-Neutral pHs“. Applied and Environmental Microbiology 70, Nr. 2 (Februar 2004): 1129–34. http://dx.doi.org/10.1128/aem.70.2.1129-1134.2004.
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ABSTRACT Fenton chemistry, which is known to play an effective role in degrading toxic chemicals, is difficult to apply to disinfection in water treatment, since its reaction is effective only at the acidic pH of 3. The presence of oxalate ions and UV-visible light, which is known as a photoferrioxalate system, allows the Fe(III) to be dissolved at slightly acidic and near-neutral pHs and maintains the catalytic reaction of iron. This study indicates that the main oxidizing species in the photoferrioxalate system responsible for microorganism inactivation is OH radical. Escherichia coli was used as an indicator microorganism. The CT value (OH radical concentration × contact time; used to indicate the effect of the combination of the concentration of the disinfectant and the contact time on inactivation) for a 2-log inactivation of E. coli was approximately 1.5 × 10−5 mg/liter/min, which is approximately 2,700 times lower than that of ozone as estimated by the delayed Chick-Watson model. Since the light emitted by the black light blue lamp is similar to sunlight in the specific wavelength range of 300 to 420 nm, the photoferrioxalate system, which can have a dual function, treating water for both organic pollutants and microorganisms simultaneously, shows promise for the treatment of water or wastewater in remote or rural sites. However, the photoferrioxalate disinfection system is slower in inactivating microorganisms than conventional disinfectants are.
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Castro, Vinicius Silva, Yhan da Silva Mutz, Denes Kaic Alves Rosario, Adelino Cunha-Neto, Eduardo Eustáquio de Souza Figueiredo und Carlos Adam Conte-Junior. „Inactivation of Multi-Drug Resistant Non-Typhoidal Salmonella and Wild-Type Escherichia coli STEC Using Organic Acids: A Potential Alternative to the Food Industry“. Pathogens 9, Nr. 10 (16.10.2020): 849. http://dx.doi.org/10.3390/pathogens9100849.
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Salmonella and Escherichia coli are the main bacterial species involved in food outbreaks worldwide. Recent reports showed that chemical sanitizers commonly used to control these pathogens could induce antibiotic resistance. Therefore, this study aimed to describe the efficiency of chemical sanitizers and organic acids when inactivating wild and clinical strains of Salmonella and E. coli, targeting a 4-log reduction. To achieve this goal, three methods were applied. (i) Disk-diffusion challenge for organic acids. (ii) Determination of MIC for two acids (acetic and lactic), as well as two sanitizers (quaternary compound and sodium hypochlorite). (iii) The development of inactivation models from the previously defined concentrations. In disk-diffusion, the results indicated that wild strains have higher resistance potential when compared to clinical strains. Regarding the models, quaternary ammonium and lactic acid showed a linear pattern of inactivation, while sodium hypochlorite had a linear pattern with tail dispersion, and acetic acid has Weibull dispersion to E. coli. The concentration to 4-log reduction differed from Salmonella and E. coli in acetic acid and sodium hypochlorite. The use of organic acids is an alternative method for antimicrobial control. Our study indicates the levels of organic acids and sanitizers to be used in the inactivation of emerging foodborne pathogens.
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Khan, Muhammad Najam, Mayuree Jaisai und Joydeep Dutta. „Photocatalytic Inactivation of Escherichia Coli Using Zinc Stannate Nanostructures under Visible Light“. Advanced Materials Research 1131 (Dezember 2015): 203–9. http://dx.doi.org/10.4028/www.scientific.net/amr.1131.203.
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Zinc stannate (ZnSnO3) nanostructured were synthesized in aqueous media at room temperature. The room temperature synthesis was designed using pourbaix diagrams. The synthesized nanoparticles were checked for their photocatalytic activity for inactivation of model microbe such asEscherichia coli (E.Coli). Photocatalytic activity was observed for zinc stannate (ZTO) in colloidal solution and ZTO deposited on glass slides. Various different concentrations of ZTO nanoparticles were used in slurry form, the bactericidal activity was observed under halogen light, room light and dark conditions. Type of light source and concentration of catalyst were observed to be the two utmost parameters for assessing the efficiency.
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BLACK, D. GLENN, X. PHILIP YE, FEDERICO HARTE und P. MICHAEL DAVIDSON. „Thermal Inactivation of Escherichia coli O157:H7 When Grown Statically or Continuously in a Chemostat“. Journal of Food Protection 73, Nr. 11 (01.11.2010): 2018–24. http://dx.doi.org/10.4315/0362-028x-73.11.2018.
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The objective of this study was to determine if survivor curves for heat-inactivated Escherichia coli O157:H7 were affected by the physiological state of the cells relative to growth conditions and pH of the heating menstruum. A comparison was made between the log-linear model and non–log-linear Weibull approach. Cells were grown statically in aerobic culture tubes or in an aerobic chemostat in tryptic soy broth (pH 7.2). The heating menstruum was unbuffered peptone or phosphate buffer (pH 7.0). Thermal inactivation was carried out at 58, 59, 60, and 61°C, and recovery was on a nonselective medium. Longer inactivation times for statically grown cells indicated potential stress adaptation. This was more prevalent at 58°C. Shape response was also significantly different, with statically grown cells exhibiting decreasing thermal resistance over time and chemostat cells showing the opposite effect. Buffering the heating menstruum to ca. pH 7 resulted in inactivation curves that showed less variability or scatter of data points. Time to specific log reduction values (td) for the Weibull model were conservative relative to the log-linear model depending upon the stage of reduction. The Weibull model offered the most accurate fit of the data in all cases, especially considering the log-linear model is equivalent to the Weibull model with a fixed shape factor of 1. The determination of z-value for the log-linear model showed a strong correlation between log D-value and process temperature. Correlations for the Weibull model parameters (log δand log p) versus process temperature were not statistically significant.
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Chapman, B., und T. Ross. „Escherichia coli and Salmonella enterica Are Protected against Acetic Acid, but Not Hydrochloric Acid, by Hypertonicity“. Applied and Environmental Microbiology 75, Nr. 11 (03.04.2009): 3605–10. http://dx.doi.org/10.1128/aem.02462-08.
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ABSTRACT Chapman et al. (B. Chapman, N. Jensen, T Ross, and M. B. Cole, Appl. Environ. Microbiol. 72:5165-5172, 2006) demonstrated that an increased NaCl concentration prolongs survival of Escherichia coli O157 SERL 2 in a broth model simulating the aqueous phase of a food dressing or sauce containing acetic acid. We examined the responses of five other E. coli strains and four Salmonella enterica strains to increasing concentrations of NaCl under conditions of lethal acidity and observed that the average “lag” time prior to inactivation decreases in the presence of hydrochloric acid but not in the presence of acetic acid. For E. coli in the presence of acetic acid, the lag time increased with increasing NaCl concentrations up to 2 to 4% at pH 4.0, up to 4 to 6% at pH 3.8, and up to 4 to 7% (wt/wt of water) NaCl at pH 3.6. Salmonella was inactivated more rapidly by combined acetic acid and NaCl stresses than E. coli, but increasing NaCl concentrations still decreased the lag time prior to inactivation in the presence of acetic acid; at pH 4.0 up to 1 to 4% NaCl was protective, and at pH 3.8 up to 1 to 2% NaCl delayed the onset of inactivation. Sublethal injury kinetics suggest that this complex response is a balance between the lethal effects of acetic acid, against which NaCl is apparently protective, and the lethal effects of the NaCl itself. Compared against 3% NaCl, 10% (wt/wt of water) sucrose with 0.5% NaCl (which has similar osmotic potential) was found to be equally protective against adverse acetic acid conditions. We propose that hypertonicity may directly affect the rate of diffusion of acetic acid into cells and hence cell survival.
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Zhou, Renwu, Xianhui Zhang, Zhenhua Bi, Zichao Zong, Jinhai Niu, Ying Song, Dongping Liu und Size Yang. „Inactivation of Escherichia coli Cells in Aqueous Solution by Atmospheric-Pressure N2, He, Air, and O2Microplasmas“. Applied and Environmental Microbiology 81, Nr. 15 (29.05.2015): 5257–65. http://dx.doi.org/10.1128/aem.01287-15.
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ABSTRACTAtmospheric-pressure N2, He, air, and O2microplasma arrays have been used to inactivateEscherichia colicells suspended in aqueous solution. Measurements show that the efficiency of inactivation ofE. colicells is strongly dependent on the feed gases used, the plasma treatment time, and the discharge power. Compared to atmospheric-pressure N2and He microplasma arrays, air and O2microplasma arrays may be utilized to more efficiently killE. colicells in aqueous solution. The efficiencies of inactivation ofE. colicells in water can be well described by using the chemical reaction rate model, where reactive oxygen species play a crucial role in the inactivation process. Analysis indicates that plasma-generated reactive species can react withE. colicells in water by direct or indirect interactions.
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POND, TREVOR J., DIANE S. WOOD, ISMAIL M. MUMIN, SHAI BARBUT und MANSEL W. GRIFFITHS. „Modeling the Survival of Escherichia coli O157:H7 in Uncooked, Semidry, Fermented Sausage“. Journal of Food Protection 64, Nr. 6 (01.06.2001): 759–66. http://dx.doi.org/10.4315/0362-028x-64.6.759.
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The data collected from studies to monitor inactivation of Escherichia coli O157:H7 in uncooked fermented salami were used to develop models to describe survival of the organism. Three models were developed that included different variables to best describe E. coli O157:H7 reduction. Model A included the variables water activity (aw), pH, time, and quadratic variables pH and time. Model B separated the processing stages into fermentation and drying. The fermentation included the variables pH and temperature × time (ttarea) and interaction between the two variables. The drying stage was modeled using the variables time and aw and interaction between the two. Model C looked at variables aw and the time at pH 5.3 to achieve a 2-D log reduction of E. coli O157:H7 and the interaction between the variables. The variables selected for inclusion in all the models were significant at the P < 0.0001 level. The predicted values for all models correlated well to the observed values with R2 of 0.888, 0.828, 0.836, and 0.818 for models A, Bferm, Bdrying, and C, respectively. The models were validated using data from a trial not used to develop the model. In general the predicted reduction in E. coli O157:H7 count in uncooked fermented salami was greater than for the observed E. coli O157:H7 log reductions for all models, but the relation between the two was linear. The results demonstrate that modeling can be a useful tool in assessing manufacturing practices for uncooked fermented salami processes.
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Rana, Yadwinder Singh, Philip M. Eberly, Quincy J. Suehr, Ian M. Hildebrandt, Bradley P. Marks und Abigail B. Snyder. „Survival of Escherichia coli O157:H7 during Moderate Temperature Dehydration of Plant-Based Foods“. Foods 10, Nr. 9 (13.09.2021): 2162. http://dx.doi.org/10.3390/foods10092162.
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The effect of moderate-temperature (≤60 °C) dehydration of plant-based foods on pathogen inactivation is unknown. Here, we model the reduction of E. coli O157:H7 as a function of product-matrix, aw, and temperature under isothermal conditions. Apple, kale, and tofu were each adjusted to aw 0.90, 0.95, or 0.99 and inoculated with an E. coli O157:H7 cocktail, followed by isothermal treatment at 49, 54.5, or 60.0 °C. The decimal reduction time, or D-value, is the time required at a given temperature to achieve a 1 log reduction in the target microorganism. Modified Bigelow-type models were developed to determine D-values which varied by product type and aw level, ranging from 3.0–6.7, 19.3–55.3, and 45.9–257.4 min. The relative impact of aw was product dependent and appeared to have a non-linear impact on D-values. The root mean squared errors of the isothermal-based models ranged from 0.75 to 1.54 log CFU/g. Second, we performed dynamic drying experiments. While the isothermal results suggested significant microbial inactivation might be achieved, the dehydrator studies showed that the combination of low product temperature and decreasing aw in the pilot-scale system provided minimal inactivation. Pilot-scale drying at 60 °C only achieved reductions of 3.1 ± 0.8 log in kale and 0.67 ± 0.66 log in apple after 8 h, and 0.69 ± 0.67 log in tofu after 24 h. This illustrates the potential limitations of dehydration at ≤60 °C as a microbial kill step.
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Corradini, Maria G., und Micha Peleg. „Dynamic Model of Heat Inactivation Kinetics for Bacterial Adaptation“. Applied and Environmental Microbiology 75, Nr. 8 (06.02.2009): 2590–97. http://dx.doi.org/10.1128/aem.02167-08.
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ABSTRACT The Weibullian-log logistic (WeLL) inactivation model was modified to account for heat adaptation by introducing a logistic adaptation factor, which rendered its “rate parameter” a function of both temperature and heating rate. The resulting model is consistent with the observation that adaptation is primarily noticeable in slow heat processes in which the cells are exposed to sublethal temperatures for a sufficiently long time. Dynamic survival patterns generated with the proposed model were in general agreement with those of Escherichia coli and Listeria monocytogenes as reported in the literature. Although the modified model's rate equation has a cumbersome appearance, especially for thermal processes having a variable heating rate, it can be solved numerically with commercial mathematical software. The dynamic model has five survival/adaptation parameters whose determination will require a large experimental database. However, with assumed or estimated parameter values, the model can simulate survival patterns of adapting pathogens in cooked foods that can be used in risk assessment and the establishment of safe preparation conditions.
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Lestini, Roxane, und Bénédicte Michel. „UvrD and UvrD252 Counteract RecQ, RecJ, and RecFOR in a rep Mutant of Escherichia coli“. Journal of Bacteriology 190, Nr. 17 (20.06.2008): 5995–6001. http://dx.doi.org/10.1128/jb.00620-08.
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ABSTRACT Rep and UvrD are two related Escherichia coli helicases, and inactivating both is lethal. Based on the observation that the synthetic lethality of rep and uvrD inactivation is suppressed in the absence of the recombination presynaptic proteins RecF, RecO, or RecR, it was proposed that UvrD is essential in the rep mutant to counteract a deleterious RecFOR-dependent RecA binding. We show here that the synthetic lethality of rep and uvrD mutations is also suppressed by recQ and recJ inactivation but not by rarA inactivation. Furthermore, it is independent of the action of UvrD in nucleotide excision repair and mismatch repair. These observations support the idea that UvrD counteracts a deleterious RecA binding to forks blocked in the rep mutant. An ATPase-deficient mutant of UvrD [uvrD(R284A)] is dominant negative in a rep mutant, but only in the presence of all RecQJFOR proteins, suggesting that the UvrD(R284A) mutant protein is deleterious when it counteracts one of these proteins. In contrast, the uvrD252 mutant (G30D), which exhibits a strongly decreased ATPase activity, is viable in a rep mutant, where it allows replication fork reversal. We conclude that the residual ATPase activity of UvrD252 prevents a negative effect on the viability of the rep mutant and allows UvrD to counteract the action of RecQ, RecJ, and RecFOR at forks blocked in the rep mutant. Models for the action of UvrD at blocked forks are proposed.
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Pothakamury, Usha R., A. Monsalve-Gonzàlez, Gustave V. Barbosa-Cánovas und Barry G. Swanson. „Inactivation of Escherichia coli and Staphylococcus aureus in model foods by pulsed electric field technology“. Food Research International 28, Nr. 2 (Januar 1995): 167–71. http://dx.doi.org/10.1016/0963-9969(95)90801-g.
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Álvarez, I., R. Virto, J. Raso und S. Condón. „Comparing predicting models for the Escherichia coli inactivation by pulsed electric fields“. Innovative Food Science & Emerging Technologies 4, Nr. 2 (Juni 2003): 195–202. http://dx.doi.org/10.1016/s1466-8564(03)00004-3.
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RODRIGO, D., G. V. BARBOSA-CÁNOVAS, A. MARTÍNEZ und M. RODRIGO. „Weibull Distribution Function Based on an Empirical Mathematical Model for Inactivation of Escherichia coli by Pulsed Electric Fields“. Journal of Food Protection 66, Nr. 6 (01.06.2003): 1007–12. http://dx.doi.org/10.4315/0362-028x-66.6.1007.
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The pulsed electric field inactivation kinetics of Escherichia coli suspended in orange juices with three different concentrations of carrot juice (0, 20, and 60%) was studied. Electric field strengths ranged from 25 to 40 kV/cm, and treatment times ranged from 40 to 340 μs. Experimental data were fitted to Bigelow, Hülsheger, and Weibull distribution functions, and the Weibull function provided the best fit (with the lowest mean square error). The dependency of each model's kinetic constant on electric field strength and carrot juice concentration was studied. A secondary model was developed to describe the relationship of Weibull parameters a and n to electric field strength and carrot juice concentration. An empirical mathematical model based on the Weibull distribution function, relating the natural logarithm of the survival fraction to treatment time, electric field strength, and carrot juice concentration, was developed. Parameters were estimated by a nonlinear regression. The results of this study indicate that the error rate for the model's predictions was 6.5% and that the model was suitable for describing E. coli inactivation.
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YOO, SUNGYUL, KASHIF GHAFOOR, JEONG UN KIM, SANGHUN KIM, BORA JUNG, DONG-UN LEE und JIYONG PARK. „Inactivation of Escherichia coli O157:H7 on Orange Fruit Surfaces and in Juice Using Photocatalysis and High Hydrostatic Pressure“. Journal of Food Protection 78, Nr. 6 (01.06.2015): 1098–105. http://dx.doi.org/10.4315/0362-028x.jfp-14-522.
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Nonpasteurized orange juice is manufactured by squeezing juice from fruit without peel removal. Fruit surfaces may carry pathogenic microorganisms that can contaminate squeezed juice. Titanium dioxide–UVC photocatalysis (TUVP), a nonthermal technique capable of microbial inactivation via generation of hydroxyl radicals, was used to decontaminate orange surfaces. Levels of spot-inoculated Escherichia coli O157:H7 (initial level of 7.0 log CFU/cm2) on oranges (12 cm2) were reduced by 4.3 log CFU/ml when treated with TUVP (17.2 mW/cm2). Reductions of 1.5, 3.9, and 3.6 log CFU/ml were achieved using tap water, chlorine (200 ppm), and UVC alone (23.7 mW/cm2), respectively. E. coli O157:H7 in juice from TUVP (17.2 mW/cm2)–treated oranges was reduced by 1.7 log CFU/ml. After orange juice was treated with high hydrostatic pressure (HHP) at 400 MPa for 1 min without any prior fruit surface disinfection, the level of E. coli O157:H7 was reduced by 2.4 log CFU/ml. However, the E. coli O157:H7 level in juice was reduced by 4.7 log CFU/ml (to lower than the detection limit) when TUVP treatment of oranges was followed by HHP treatment of juice, indicating a synergistic inactivation effect. The inactivation kinetics of E. coli O157:H7 on orange surfaces followed a biphasic model. HHP treatment did not affect the pH, °Brix, or color of juice. However, the ascorbic acid concentration and pectinmethylesterase activity were reduced by 35.1 and 34.7%, respectively.
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CHAPMAN, B., K. J. SCURRAH und T. ROSS. „Contemporary Formulation and Distribution Practices for Cold-Filled Acid Products: Australian Industry Survey and Modeling of Published Pathogen Inactivation Data“. Journal of Food Protection 73, Nr. 5 (01.05.2010): 895–906. http://dx.doi.org/10.4315/0362-028x-73.5.895.
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A survey of 12 Australian manufacturers indicated that mild-tasting acids and preservatives are used to partially replace acetic acid in cold-filled acid dressings and sauces. In contrast to traditional ambient temperature distribution practices, some manufacturers indicated that they supply the food service sector with cold-filled acid products prechilled for incorporation into ready-to-eat foods. The Comité des Industries des Mayonnaises et Sauces Condimentaires de la CommunautéÉconomique Européenne (CIMSCEE) Code, a formulation guideline used by the industry to predict the safety of cold-filled acid formulations with respect to Salmonella enterica and Escherichia coli, does not extend to the use of acids and preservatives other than acetic acid nor does it consider the effects of chill distribution. We found insufficient data in the published literature to comprehensively model the response of S. enterica and E. coli to all of the predictor variables (i.e., pH, acetic acid, NaCl, sugars, other acids, preservatives, and storage temperature) of relevance for contemporary cold-filled acid products in Australia. In particular, we noted a lack of inactivation data for S. enterica at aqueous-phase NaCl concentrations of >3% (wt/wt). However, our simple models clearly identified pH and 1/absolute temperature of storage as the most important variables generally determining inactivation. To develop robust models to predict the effect of contemporary formulation and storage variables on product safety, additional empirical data are required. Until such models are available, our results support challenge testing of cold-filled acid products to ascertain their safety, as suggested by the CIMSCEE, but suggest consideration of challenging with both E. coli and S. enterica at incubation temperatures relevant to intended product distribution temperatures.
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HAN, Y., J. D. FLOROS, R. H. LINTON, S. S. NIELSEN und P. E. NELSON. „Response Surface Modeling for the Inactivation of Escherichia coli O157:H7 on Green Peppers (Capsicum annuum L.) by Chlorine Dioxide Gas Treatments†“. Journal of Food Protection 64, Nr. 8 (01.08.2001): 1128–33. http://dx.doi.org/10.4315/0362-028x-64.8.1128.
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The effects of chlorine dioxide (ClO2) gas concentration (0.1 to 0.5 mg/liter), relative humidity (RH) (55 to 95%), treatment time (7 to 135 min), and temperature (5 to 25°C) on inactivation of Escherichia coli O157:H7 on green peppers were studied using response surface methods. A four-factor, central, composite, rotatable design was used. The microbial log reduction was measured as a response. A direct membrane-surface-plating method with tryptic soy agar and sorbitol Mac-Conkey agar was used to resuscitate and enumerate ClO2-treated E. coli O157:H7 cells. The statistical analysis and the predictive model developed in this study suggest that ClO2 gas concentration, treatment time, RH, and temperature all significantly (P < 0.01) increased the inactivation of E. coli O157:H7. ClO2 gas concentration was the most important factor, whereas temperature was the least significant. The interaction between ClO2 gas concentration and RH indicated a synergistic effect. The predictive model was validated, and it could be used to determine effective ClO2 gas treatments to achieve a 5-log reduction of E. coli O157:H7 on green peppers.
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GRIEßLER, Richard, Sabato D'AURIA, Reinhard SCHINZEL, Fabio TANFANI und Bernd NIDETZKY. „Mechanism of thermal denaturation of maltodextrin phosphorylase from Escherichia coli“. Biochemical Journal 346, Nr. 2 (22.02.2000): 255–63. http://dx.doi.org/10.1042/bj3460255.
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Maltodextrin phosphorylase from Escherichia coli (MalP) is a dimeric protein in which each ≈ 90-kDa subunit contains active-site pyridoxal 5ʹ-phosphate. To unravel factors contributing to the stability of MalP, thermal denaturations of wild-type MalP and a thermostable active-site mutant (Asn-133 → Ala) were compared by monitoring enzyme activity, cofactor dissociation, secondary structure content and aggregation. Small structural transitions of MalP are shown by Fourier-transform infrared spectroscopy to take place at ≈ 45 °C. They are manifested by slight increases in unordered structure and 1H/2H exchange, and reflect reversible inactivation of MalP. Aggregation of the MalP dimer is triggered by these conformational changes and starts at ≈ 45 °C without prior release into solution of pyridoxal 5ʹ-phosphate. It is driven by electrostatic rather than hydrophobic interactions between MalP dimers, and leads to irreversible inactivation of the enzyme. Aggregation is inhibited efficiently and specifically by oxyanions such as phosphate, and AMP which therefore, stabilize MalP against the irreversible denaturation step at 45 °C. Melting of the secondary structure in soluble and aggregated MalP takes place at much higher temperatures of approx. 58 and 67 °C, respectively. Replacement of Asn-133 by Ala does not change the mechanism of thermal denaturation, but leads to a shift of the entire pathway to a ≈ 15 °C higher value on the temperature scale. Apart from greater stability, the Asn-133 → Ala mutant shows a 2-fold smaller turnover number and a 4.6-fold smaller energy of activation than wild-type MalP, probably indicating that the site-specific replacement of Asn-133 brings about a greater rigidity of the active-site environment of the enzyme. A structure-based model is proposed which explains the stabilizing interaction between MalP and oxyanions, or AMP.
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Loc, Dang Thi Thanh, Le Van Tuan, Hidenori Harada, Duong Van Hieu, Pham Khac Lieu und Duong Thanh Chung. „ENHANCEMENT OF WATER DISINFECTION EFFICIENCY USING UV RADIATION WITH THE AID OF A LIQUID-FILM-FORMING DEVICE“. Vietnam Journal of Science and Technology 58, Nr. 3A (25.05.2020): 203. http://dx.doi.org/10.15625/2525-2518/58/3a/14420.
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This study presents results for the use of UV radiation and a liquid-film-forming device (LFFD) for disinfection of water. Escherichia coli was used as a model microorganism for examining the bactericidal performance of UV. Bacterial inactivation was conducted in a LFFD with various condition of UV dosages, air flow rates, and initial bacterial concentrations. Combined UV/LFFD treatments resulted in a greater inactivation efficiency than those for the UV treatment alone. Combined treatment with UV (UV dosage = 3.020×10-20 kJ/m2, initial bacterial concentration = 1.1×105 – 2.2×105 CFU/mL, and room temperature) and LFFD (air flow rate = 2400 L/min) caused 89% inactivation in terms of the bacterial load. In contrast, when the UV treatment was used, only 29% of the E. coli load was inactivated. These findings suggest that the combined UV/LFFD treatments could provide a promising method for water disinfection.
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KOSEKI, SHIGENOBU, NOBUTAKA NAKAMURA und TAKEO SHIINA. „Comparison of Desiccation Tolerance among Listeria monocytogenes, Escherichia coli O157:H7, Salmonella enterica, and Cronobacter sakazakii in Powdered Infant Formula“. Journal of Food Protection 78, Nr. 1 (01.01.2015): 104–10. http://dx.doi.org/10.4315/0362-028x.jfp-14-249.
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Bacterial pathogens such as Listeria monocytogenes, Escherichia coli O157:H7, Salmonella enterica, and Cronobacter sakazakii have demonstrated long-term survival in/on dry or low–water activity (aw) foods. However, there have been few comparative studies on the desiccation tolerance among these bacterial pathogens separately in a same food matrix. In the present study, the survival kinetics of the four bacterial pathogens separately inoculated onto powdered infant formula as a model low-aw food was compared during storage at 5, 22, and 35°C. No significant differences in the survival kinetics between E. coli O157:H7 and L. monocytogenes were observed. Salmonella showed significantly higher desiccation tolerance than these pathogens, and C. sakazakii demonstrated significantly higher desiccation tolerance than all other three bacteria studied. Thus, the desiccation tolerance was represented as C. sakazakii > Salmonella > E. coli O157:H7 = L. monocytogenes. The survival kinetics of each bacterium was mathematically analyzed, and the observed kinetics was successfully described using the Weibull model. To evaluate the variability of the inactivation kinetics of the tested bacterial pathogens, the Monte Carlo simulation was performed using assumed probability distribution of the estimated fitted parameters. The simulation results showed that the storage temperature significantly influenced survival of each bacterium under the dry environment, where the bacterial inactivation became faster with increasing storage temperature. Furthermore, the fitted rate and shape parameters of the Weibull model were successfully modelled as a function of temperature. The numerical simulation of the bacterial inactivation was realized using the functions of the parameters under arbitrary fluctuating temperature conditions.
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MURAKAMI, EDGAR G., LAUREN JACKSON, KEVIN MADSEN und BRIAN SCHICKEDANZ. „FACTORS AFFECTING THE ULTRAVIOLET INACTIVATION OF ESCHERICHIA COLI K12 IN APPLE JUICE AND A MODEL SYSTEM*“. Journal of Food Process Engineering 29, Nr. 1 (Februar 2006): 53–71. http://dx.doi.org/10.1111/j.1745-4530.2006.00049.x.
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Zhong, Kui, Fang Chen, Zhengfu Wang, Jihong Wu, Xiaojun Liao und Xiaosong Hu. „Inactivation and kinetic model for the Escherichia coli treated by a co-axial pulsed electric field“. European Food Research and Technology 221, Nr. 6 (10.08.2005): 752–58. http://dx.doi.org/10.1007/s00217-005-0015-0.
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DUFFY, SIOBAIN, JOHN CHUREY, RANDY W. WOROBO und DONALD W. SCHAFFNER. „Analysis and Modeling of the Variability Associated with UV Inactivation of Escherichia coli in Apple Cider“. Journal of Food Protection 63, Nr. 11 (01.11.2000): 1587–90. http://dx.doi.org/10.4315/0362-028x-63.11.1587.
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Raw data from validation studies of UV tubes used for nonthermal pathogen reduction in apple cider underwent comprehensive statistical analysis. Data from each tube that demonstrated at least a 5-log reduction of Escherichia coli ATCC 25922, a surrogate for E. coli O157:H7, in each of three trials were used in the analysis. The within- and between-tube variability was calculated for 70 tubes. The mean log reductions of the tubes fit a Beta distribution (Kolmogorov-Smirnov test, 0.0246), and the between-replicate variability followed a logistic distribution (Kolmogorov-Smirnov test, 0.0305). These two distributions can be used together to model UV cider treatment as part of an overall E. coli O157:H7 in cider risk assessment. Examples of codes from @RISK and Analytica to describe these distributions, such as one would find in a quantitative risk assessment, are included.
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CHUNG, HYUN-JUNG, SHAOJIN WANG und JUMING TANG. „Influence of Heat Transfer with Tube Methods on Measured Thermal Inactivation Parameters for Escherichia coli“. Journal of Food Protection 70, Nr. 4 (01.04.2007): 851–59. http://dx.doi.org/10.4315/0362-028x-70.4.851.
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The purpose of this study was to investigate the influence of heat transfer on measured thermal inactivation kinetic parameters of bacteria in solid foods when using tube methods. The bacterial strain selected for this study, Escherichia coli K-12, had demonstrated typical first-order inactivation characteristics under isothermal test conditions. Three tubes of different sizes (3, 13, and 20 mm outer diameter) were used in the heat treatments at 57, 60, and 63°C with mashed potato as the test food. A computer model was developed to evaluate the effect of transit heat transfer behavior on microbial inactivation in the test tubes. The results confirmed that the survival curves of E. coli K-12 obtained in 3-mm capillary tubes were log linear at the three tested temperatures. The survival curves observed under nonisothermal conditions in larger tubes were no longer log linear. Slow heat transfer alone could only partially account for the large departures from log-linear behavior. Tests with the same bacterial strain after 5 min of preconditioning at a sublethal temperature of 45°C revealed significantly enhanced heat resistance. Confirmative tests revealed that the increased heat resistance of the test bacterium in the center of the large tubes during the warming-up periods resulted in significantly larger D-values than those obtained with capillary tube methods.
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Wroński, G., K. Budzińska, B. Szejniuk und A. Jurek. „Influence of temperature on survival of Escherichia coli O157:H7 in stored cattle slurry with respect to environmental biosafety“. Polish Journal of Veterinary Sciences 15, Nr. 4 (01.12.2012): 797–98. http://dx.doi.org/10.2478/v10181-012-0124-1.
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Abstract The aim of the study was to determine the influence of temperature, i.e. 4 and 20oC on the Escherichia coli O157:H7 survival time in a stored cattle slurry in a laboratory model experiment. The results of this investigation indicated that the tested microorganisms underwent a gradual elimination in the cattle slurry, whereas their inactivation rate was clearly dependent on the temperature. A higher survival rate was found in Escherichia coli O157:H7 at 4oC where a theoretical survival time of these microorganisms, determined using a regression analysis, amounted to 83 days. Our study indicates that there is a necessity for the slurry to undergo hygienization processes and that a constant monitoring of liquid animal excreta in search for pathogenic microorganisms is required.
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ZHONG, QIXIN, D. GLENN BLACK, P. MICHAEL DAVIDSON und DAVID A. GOLDEN. „Nonthermal Inactivation of Escherichia coli K-12 on Spinach Leaves, Using Dense Phase Carbon Dioxide“. Journal of Food Protection 71, Nr. 5 (01.05.2008): 1015–17. http://dx.doi.org/10.4315/0362-028x-71.5.1015.
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While the use of some chemical sanitizers is approved for inactivation of microbes on the surfaces of fruits and vegetables, these compounds often degrade product quality with limited improvement in product safety. The application of dense phase carbon dioxide (DPCD, or high-pressure CO2) is a nonthermal process for inactivation of foodborne pathogens inoculated into various juices and model solutions. In this work, DPCD was evaluated for its potential to inactivate Escherichia coli K-12 inoculated on fresh spinach leaves. Inoculated leaves were exposed for up to 40 min to DPCD at a subcritical condition (5 MPa, 40°C) and two supercritical conditions (7.5 and 10 MPa, 40°C) at a flow rate of 50 g of CO2/min. E. coli K-12 populations were reduced to nondetectable levels (~5-log reduction) using supercritical treatment conditions at exposure times as short as 10 min; efficacy of DPCD at the subcritical state was limited. This research demonstrates that DPCD has potential as a pasteurization technology for application to leafy green vegetables, although issues with discoloration and other quality measures will need more extensive evaluations.
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LIU, HUI, RUIQIANG MENG, JIAYING WANG, YAN D. NIU, JINQUAN LI, KIM STANFORD und TIM A. McALLISTER. „Inactivation of Escherichia coli O157 Bacteriophages by Using a Mixture of Ferrous Sulfate and Tea Extract“. Journal of Food Protection 78, Nr. 12 (01.12.2015): 2220–26. http://dx.doi.org/10.4315/0362-028x.jfp-15-239.
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Bacteriophages (phages) have been used for biocontrol of Escherichia coli O157 and other pathogenic bacteria in many different matrices and foods, but few studies have included inactivation of residual phages in culture medium before plating and enumeration of surviving host bacteria for the assessment of phage efficacy. This oversight may lead to overestimation of phage efficacy. The ability of virucidal solution containing a mixture of ferrous sulfate [iron(II) sulfate, FeSO4] and tea extract [Fe(II)T] to inactivate residual T5-like, T1-like, T4-like, and rV5-like phages was assessed using E. coli O157 as the host. At concentrations of ≥10 mM FeSO4, all phages were not detected after 20 min in a broth culture model. Compared with the virucidal solution–free samples (1 to 96% recovery), Fe(II)T (10 mM FeSO4 plus 15% tea extract) recovered a greater (P < 0.01) number of E. coli O157 from phage-treated broth culture (97 to 100% recovery) and beef samples (52 to 100% recovery). Moreover, with the addition of Fe(II)T, the number of bacteria surviving after exposure to T5-like or T4-like phages was greater (P < 0.01) than that after exposure to T1-like or rV5-like phages. Consequently, use of a virucide for phage inactivation is recommended to improve the accuracy of evaluations of phage efficacy for biocontrol of E. coli O157.
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Janus, Magdalena, Ewelina Kusiak-Nejman, Paulina Rokicka-Konieczna, Agata Markowska-Szczupak, Kamila Zając und Antoni W. Morawski. „Bacterial Inactivation on Concrete Plates Loaded with Modified TiO2 Photocatalysts under Visible Light Irradiation“. Molecules 24, Nr. 17 (21.08.2019): 3026. http://dx.doi.org/10.3390/molecules24173026.
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The antibacterial activity of concrete plates loaded with various titania photocatalysts was investigated. The target in bacteria testing was Escherichia coli K12. The presence of photocatalysts in the concrete matrix at a dose of 10 wt.% improved the antibacterial properties, which became significant depending on the type of the added photocatalyst. Total inactivation of E. coli irradiated under artificial solar light was observed on the concrete plates loaded with the following photocatalysts: TiO2/N,CMeOH-300, TiO2/N,CEtOH-100, TiO2/N,CisoPrOH-100 and TiO2/N-300. The modified Hom disinfection kinetic model was found as a best-fit model for the obtained results. The presence of nitrogen and carbon in the photocatalysts structure, as well as crystallite size, surface area and porosity, contributed to the increase of antibacterial properties of concrete plates.
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MUKHERJEE, AVIK, YOHAN YOON, KEITH E. BELK, JOHN A. SCANGA, GARY C. SMITH und JOHN N. SOFOS. „Thermal Inactivation of Escherichia coli O157:H7 in Beef Treated with Marination and Tenderization Ingredients“. Journal of Food Protection 71, Nr. 7 (01.07.2008): 1349–56. http://dx.doi.org/10.4315/0362-028x-71.7.1349.
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Internalization of Escherichia coli O157:H7 in nonintact beef products during mechanical tenderization or during injection of marination and tenderization ingredients is of concern if such products are undercooked. This study tested organic acids (0.2% citric acid and 0.3% acetic acid), potassium and calcium salts (1.8% potassium lactate, 0.63% calcium lactate, 0.86% calcium ascorbate, and 0.23% calcium chloride), and sodium chloride (2.5%) for their influence on thermal destruction of E. coli O157:H7 in ground beef serving as a model system. Ground beef batches (700 g; 5% fat) were mixed with equal volumes (22 ml) of each treatment solution or distilled water and portions (30 g) of treated ground beef were extruded in test tubes (2.5 by 10 cm). A five-strain mixture of E. coli O157:H7 (0.3 ml; 7 log CFU/g) was introduced at the center of the sample with a pipette. After overnight storage (4°C), simulating product marination, samples were heated to 60 or 65°C internal temperature, simulating rare and medium rare doneness of beef, in a circulating water bath. At 65°C, treatments with citric and acetic acid showed greater (P < 0.05) reduction (4 to 5 log CFU/g) of E. coli O157:H7 than all the other ingredients and the control (3 to 4 log CFU/g). Sodium chloride reduced weight losses (16 to 18% compared with 20 to 27% by citric or acetic acid) and resulted in a 4-log reduction in counts during cooking to 65°C. Ingredients such as citric or acetic acid may improve thermal inactivation of E. coli O157:H7 internalized in nonintact beef products, while sodium chloride may reduce cooking losses in such products.
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HA, JAE-WON, und DONG-HYUN KANG. „Inactivation Kinetics of Escherichia coli O157:H7, Salmonella enterica Serovar Typhimurium, and Listeria monocytogenes in Ready-to-Eat Sliced Ham by Near-Infrared Heating at Different Radiation Intensities“. Journal of Food Protection 77, Nr. 7 (01.07.2014): 1224–28. http://dx.doi.org/10.4315/0362-028x.jfp-13-561.
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The aim of this study was to investigate the inactivation kinetics of Salmonella enterica serovar Typhimurium, Escherichia coli O157:H7, and Listeria monocytogenes on ready-to-eat sliced ham by near-infrared (NIR) heating as a function of the processing parameter, radiation intensity. Precooked ham slices inoculated with the three pathogens were treated at different NIR intensities (ca. 100, 150, and 200 μW/cm2/nm). An increase in the applied radiation intensity resulted in a gradual increase of inactivation of all pathogens. The survival curves of the three pathogens exhibited both shoulder and tailing behavior at all light intensities. Among nonlinear models, the Weibull distribution and log-logistic model were used to describe the experimental data, and the statistical results (mean square error and R2 values) indicated the suitability of the model for prediction. The log-logistic model more accurately described survival curves of the three pathogens than did the Weibull distribution at all radiation intensities. The output of this study and the proposed kinetics model would be beneficial to the deli meat industry for selecting the optimum processing conditions of NIR heating to meet the target pathogen inactivation on ready-to-eat sliced ham.
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NAIM, FADIA, SERGE MESSIER, LINDA SAUCIER und GABRIEL PIETTE. „A Model Study of Escherichia coli O157:H7 Survival in Fermented Dry Sausages—Influence of Inoculum Preparation, Inoculation Procedure, and Selected Process Parameters“. Journal of Food Protection 66, Nr. 12 (01.12.2003): 2267–75. http://dx.doi.org/10.4315/0362-028x-66.12.2267.
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The influence of inoculum preparation, inoculation level, and inoculation procedure on Escherichia coli O157:H7 inactivation during the manufacture of fermented sausage was evaluated in a model study. Prior growth in glucose-enrichedtryptone soya broth, which provided exposure to mildly acidic conditions (pH 4.8), had no effect on the later survival of E. coli O157: H7 strains 5-1 and ATCC 43894 under extremely acidic conditions (pH 2), but the same strains became sensitive to acidity after 7 days of incubation on the surface of refrigerated beef (as per the normal contamination route from slaughter to further processing). In subsequent sausage production trials, the extent of destruction observed for E. coli O157:H7 strains F-90, 5-1, and ATCC 43894 inoculated directly into the meat batter was unchanged when the inoculation level was decreased from 7.3 to 4.7 log CFU/g, but the level of inactivation was ca. 1 log higher when the surfaces of beef cuts, rather than the batter, were inoculated 7 days prior to processing. Regardless of processing conditions (fermentation to a pH of ≤5.0 at 24 or 37°C, drying at 14°C to a water activity [aw] value of 0.91 or 0.79), strains F-90, 5-1, and ATCC 43894 showed similar survival capacities during the manufacture of sausage. A ~2-log reduction in pathogen numbers was generally obtained after samples were dried to an aw of 0.91, irrespective of fermentation temperature. The addition of a 5-day predrying holding stage at the fermentation temperature significantly (P < 0.05) increased pathogen inactivation when fermentation was carried out at 37°C (but not when it was carried out at 24°C). However, significant pathogen reductions (4 to 5 log CFU/g) were achieved only for extensively dried products (aw = 0.79).
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Bhullar, Manreet S., Ankit Patras, Agnes Kilonzo-Nthenge, Bharat Pokharel und Michael Sasges. „Ultraviolet inactivation of bacteria and model viruses in coconut water using a collimated beam system“. Food Science and Technology International 25, Nr. 7 (08.05.2019): 562–72. http://dx.doi.org/10.1177/1082013219843395.
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This study investigated the effect of ultraviolet-C irradiation on the inactivation of microorganisms in coconut water, a highly opaque liquid food (1.01 ± 0.018 absorption coefficient). Ultraviolet-C inactivation kinetics of two bacteriophages (MS2, T1UV) and three surrogate bacteria ( Escherichia coli, Salmonella Typhimurium, Listeria monocytogenes) in 0.1% (w/v) peptone and coconut water were investigated. Ultraviolet-C irradiation at 254 nm was applied to stirred samples, using a collimated beam device. A series of known ultraviolet-C doses (0–40 mJ cm−2) were applied for ultraviolet-C treatment except for MS2 where higher doses were delivered (100 mJ cm−2). Inactivation levels of all organisms were proportional to ultraviolet-C dose. At the highest dose of 40 mJ cm−2, three surrogates of pathogenic bacteria were inactivated by more than 5-log10 (p < 0.05) in 0.1% (w/v) peptone and coconut water. Results showed that ultraviolet-C irradiation effectively inactivated bacteriophage and surrogate bacteria in highly opaque coconut water. The log reduction kinetics of microorganisms followed log-linear and exponential models with higher R2 (>0.95) and low root mean square error values. The D10 values of 3, 5.48, and 4.58 mJ cm−2 were obtained from the inactivation of E. coli, S. Typhimurium, and L. monocytogenes, respectively. Models for predicting log reduction as a function of ultraviolet-C irradiation dose were found to be significant (p < 0.05). Fluid optics were the key controlling parameters for efficient microbial inactivation. Therefore, the ultraviolet-C dose must be calculated not only from the incident ultraviolet-C intensity but must also consider the attenuation in the samples. The results from this study imply that adequate log reduction of vegetative cells and model viruses is achievable in coconut water and suggested significant potential for ultraviolet-C treatment of other liquid foods.
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DE LAMO-CASTELLVÍ, SÍLVIA, MARTA CAPELLAS, ARTUR X. ROIG-SAGUÉS, TOMÁS LÓPEZ-PEDEMONTE, M. MANUELA HERNÁNDEZ-HERRERO und BUENAVENTURA GUAMIS. „Fate of Escherichia coli Strains Inoculated in Model Cheese Elaborated with or without Starter and Treated by High Hydrostatic Pressure“. Journal of Food Protection 69, Nr. 12 (01.12.2006): 2856–64. http://dx.doi.org/10.4315/0362-028x-69.12.2856.
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The aim of this research was to study high hydrostatic pressure inactivation of two strains of Escherichia coli (E. coli O59:H21 [CECT 405] and E. coli O157:H7 [CECT 5947]) inoculated in washed-curd model cheese elaborated with and without starter and the ability of these strains for survival, recovery, and growth. Samples were treated at 300, 400, and 500 MPa for 10 min at 20°C and analyzed after the treatment and after 1, 7, and 15 days of storage at 8°C to study the behavior of Escherichia populations. Cheeses elaborated with starter showed the maximum lethality at 400 and 500 MPa, and no significant differences in the baroresistant behavior of either strains were detected, except for E. coli O157:H7 at 400 MPa in cell counts obtained with thin agar layer method medium, where the decrease value was significantly lower. In cheese elaborated without starter, the highest decrease value was observed at 500 MPa, except for E. coli O59:H21 in cell counts obtained with selective culture medium, where the highest decrease value was also found at 400 MPa. The ability to repair and grow was not observed in model cheese elaborated with starter, as cell counts of treated samples decreased after 15 days of storage at 8°C. By contrast, in cheese elaborated without starter, all pressurized samples showed the trend to repair and grow during the storage period in both strains. These results suggest that the presence of starter and low pH values are the main factors that control the ability of Escherichia strains inoculated in this type of cheese and treated by high hydrostatic pressure to recover and grow.
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K. L. Bialka, A. Demirci, P. N. Walker und V. M. Puri. „Pulsed UV-Light Penetration of Characterization and the Inactivation of Escherichia coli K12 in Solid Model Systems“. Transactions of the ASABE 51, Nr. 1 (2008): 195–204. http://dx.doi.org/10.13031/2013.24204.
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Nunes Silva, Beatriz, Vasco Cadavez, José António Teixeira und Ursula Gonzales-Barron. „Effects of Essential Oils on Escherichia coli Inactivation in Cheese as Described by Meta-Regression Modelling“. Foods 9, Nr. 6 (02.06.2020): 716. http://dx.doi.org/10.3390/foods9060716.
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The growing intention to replace chemical food preservatives with plant-based antimicrobials that pose lower risks to human health has produced numerous studies describing the bactericidal properties of biopreservatives such as essential oils (EOs) in a variety of products, including cheese. This study aimed to perform a meta-analysis of literature data that could summarize the inactivation of Escherichia coli in cheese achieved by added EOs; and compare its inhibitory effectiveness by application method, antimicrobial concentration, and specific antimicrobials. After a systematic review, 362 observations on log reduction data and study characteristics were extracted from 16 studies. The meta-regression model suggested that pathogenic E. coli is more resistant to EO action than the non-pathogenic type (p < 0.0001), although in both cases the higher the EO dose, the greater the mean log reduction achieved (p < 0.0001). It also showed that, among the factual application methods, EOs’ incorporation in films render a steadier inactivation (p < 0.0001) than when directly applied to milk or smeared on cheese surface. Lemon balm, sage, shallot, and anise EOs showed the best inhibitory outcomes against the pathogen. The model also revealed the inadequacy of inoculating antimicrobials in cheese purposely grated for performing challenge studies, as this non-realistic application overestimates (p < 0.0001) the inhibitory effects of EOs.
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ADHIKARI, ACHYUT, ANDY BARY, CRAIG COGGER, CALEB JAMES, GÜLHAN ÜNLÜ und KAREN KILLINGER. „Thermal and Starvation Stress Response of Escherichia coli O157:H7 Isolates Selected from Agricultural Environments“. Journal of Food Protection 79, Nr. 10 (01.10.2016): 1673–79. http://dx.doi.org/10.4315/0362-028x.jfp-16-115.
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ABSTRACT Pathogens exposed to agricultural production environments are subject to multiple stresses that may alter their survival under subsequent stress conditions. The objective of this study was to examine heat and starvation stress response of Escherichia coli O157:H7 strains isolated from agricultural matrices. Seven E. coli O157:H7 isolates from different agricultural matrices—soil, compost, irrigation water, and sheep manure—were selected, and two ATCC strains were used as controls. The E. coli O157:H7 isolates were exposed to heat stress (56°C in 0.1% peptone water for up to 1 h) and starvation (in phosphate-buffered saline at 37°C for 15 days), and their survival was examined. GInaFiT freeware tool was used to perform regression analyses of the surviving populations. The Weibull model was identified as the most appropriate model for response of the isolates to heat stress, whereas the biphasic survival curves during starvation were fitted using the double Weibull model, indicating the adaptation to starvation or a resistant subpopulation. The inactivation time during heating to achieve the first decimal reduction time (δ) calculated with the Weibull parameters was the highest (45 min) for a compost isolate (Comp60A) and the lowest (28 min) for ATCC strain 43895. Two of the nine isolates (ATCC 43895 and a manure isolate) had β < 1, indicating that surviving populations adapted to heat stress, and six strains demonstrated downward concavity (β > 1), indicating decreasing heat resistance over time. The ATCC strains displayed the longest δ2 (>1,250 h) in response to starvation stress, compared with from 328 to 812 h for the environmental strains. The considerable variation in inactivation kinetics of E. coli O157:H7 highlights the importance of evaluating response to stress conditions among individual strains of a specific pathogen. Environmental isolates did not exhibit more robust response to stress conditions in this study compared with ATCC strains.