scholarly journals Isolation of Highly Heat-Resistant Listeria monocytogenes Variants by Use of a Kinetic Modeling-Based Sampling Scheme

2011 ◽  
Vol 77 (8) ◽  
pp. 2617-2624 ◽  
Author(s):  
Ineke K. H. Van Boeijen ◽  
Christof Francke ◽  
Roy Moezelaar ◽  
Tjakko Abee ◽  
Marcel H. Zwietering
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
Kinetic Modeling ◽  
High Resistance ◽  
High Hydrostatic Pressure ◽  
Heat Inactivation ◽  
Inactivation Kinetics ◽  
Wild Type ◽  
Content Type ◽  
Heat Resistant

ABSTRACTStable high-hydrostatic-pressure (HHP)-resistantListeria monocytogenesLO28 variants were previously isolated and characterized. These HHP variants were also more resistant to heat. In addition, nonlinear heat inactivation kinetics pointed toward the existence of heat-resistant variants, although these could not be isolated so far. In this study, we used kinetic modeling of inactivation curves of two isolated HHP variants and their wild type, and this revealed that the probability of finding resistant variants should depend on the nature of the inactivation treatment and the time of exposure. At specific heat and HHP conditions, resistant LO28 and EGDe variants were indeed isolated. Resistant LO28 variants were even isolated after a heat inactivation at 72°C in milk, and these variants showed high resistance to standard pasteurization conditions. The increased resistance of part of the isolated LO28 and EGDe variants was due to mutations in theirctsRgenes. For the variants whosectsRgenes and upstream regions were not altered, the mechanisms leading to increased resistance remain to be elucidated. This research showed the strength of kinetic modeling in unraveling the causes of nonlinear inactivation and facilitating the isolation of heat-resistantL. monocytogenesvariants.

Inactivation Kinetics of Three Listeria monocytogenes Strains under High Hydrostatic Pressure

2008 ◽  
Vol 71 (10) ◽  
pp. 2007-2013 ◽  
Author(s):  
INEKE K. H. VAN BOEIJEN ◽  
ROY MOEZELAAR ◽  
TJAKKO ABEE ◽  
MARCEL H. ZWIETERING
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Inactivation Kinetics ◽  
Wild Type ◽  
First Order Kinetics ◽  
Survival Capacity ◽  
D Values ◽  
Kinetics Of ◽  
Stable Feature

High hydrostatic pressure (HHP) inactivation of three Listeria monocytogenes strains (EGDe, LO28, and Scott A) subjected to 350 MPa at 20°C in ACES buffer resulted in survival curves with significant tailing for all three strains. A biphasic linear model could be fitted to the inactivation data, indicating the presence of an HHP-sensitive and an HHP-resistant fraction, which both showed inactivation according to first-order kinetics. Inactivation parameters of these subpopulations of the three strains were quantified in detail. EGDe showed the highest D-values for the sensitive and resistant fraction, whereas LO28 and Scott A showed lower HHP resistance for both fractions. Survivors isolated from the tail of LO28 and EGDe were analyzed, and it was revealed that the higher resistance of LO28 was a stable feature for 24% (24 of 102) of the resistant fraction. These HHP-resistant variants were 10 to 600,000 times more resistant than wild type when exposed to 350 MPa at 20°C for 20 min. Contrary to these results, no stable HHP-resistant isolates were found for EGDe (0 of 102). The possible effect of HHP survival capacity of stress-resistant genotypic and phenotypic variants of L. monocytogenes on the safety of HHP-processed foods is discussed.

scholarly journals Identification of Sigma Factor σB-Controlled Genes and Their Impact on Acid Stress, High Hydrostatic Pressure, and Freeze Survival in Listeria monocytogenes EGD-e

2004 ◽  
Vol 70 (6) ◽  
pp. 3457-3466 ◽  
Author(s):  
Henrike H. Wemekamp-Kamphuis ◽  
Jeroen A. Wouters ◽  
Patrick P. L. A. de Leeuw ◽  
Torsten Hain ◽  
Trinad Chakraborty ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
Sigma Factor ◽  
High Hydrostatic Pressure ◽  
Glutamate Decarboxylase ◽  
Expression Profiles ◽  
Pressure Treatment ◽  
Wild Type ◽  
High Hydrostatic Pressure Treatment ◽  
The Impact

ABSTRACT The gene encoding the alternative sigma factor σB in Listeria monocytogenes is induced upon exposure of cells to several stresses. In this study, we investigated the impact of a sigB null mutation on the survival of L. monocytogenes EGD-e at low pH, during high-hydrostatic-pressure treatment, and during freezing. The survival of ΔsigB mutant exponential-phase cells at pH 2.5 was 10,000-fold lower than the survival of EGD-e wild-type cells. Moreover, the ΔsigB mutant failed to show an acid tolerance response. Upon preexposure for 1 h to pH 4.5, the survival at pH 2.5 was 100,000-fold lower for the ΔsigB mutant than for the wild type. The glutamate decarboxylase (GAD) acid resistance system is important in survival and adaptation of L. monocytogenes in acidic conditions. The σB dependence of the gad genes (gadA, gadB, gadC, gadD, and gadE) was analyzed in silico. Putative σB-dependent promoter sites were found upstream of the gadCB operon (encoding a glutamate/γ-aminobutyrate antiporter and a glutamate decarboxylase, respectively) and the lmo2434 gene (gadD, encoding a putative glutamate decarboxylase). Reverse transcriptase PCR revealed that expression of the gadCB operon and expression of gadD are indeed σB dependent. In addition, a proteomics approach was used to analyze the protein expression profiles upon acid exposure. Although the GAD proteins were not recovered, nine proteins accumulated in the wild type but not in the ΔsigB strain. These proteins included Pfk, GalE, ClpP, and Lmo1580. Exposure to pH 4.5, in order to preload cells with active σB and consequently with σ B-dependent general stress proteins, also provided considerable protection against high-hydrostatic-pressure treatment and freezing. The combined data argue that the expression of σB-dependent genes provides L. monocytogenes with nonspecific multiple-stress resistance that may be relevant for survival in the natural environment as well as during food processing.

scholarly journals Avoidance of Autophagy Mediated by PlcA or ActA Is Required for Listeria monocytogenes Growth in Macrophages

2015 ◽  
Vol 83 (5) ◽  
pp. 2175-2184 ◽  
Author(s):  
Gabriel Mitchell ◽  
Liang Ge ◽  
Qiongying Huang ◽  
Chen Chen ◽  
Sara Kianian ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Wild Type Strain ◽  
Fold Increase ◽  
Host Cells ◽  
Listeriolysin O ◽  
Wild Type ◽  
Conjugation System ◽  
Content Type ◽  
A Cell ◽  
Gain Access

Listeria monocytogenesis a facultative intracellular pathogen that escapes from phagosomes and grows in the cytosol of infected host cells. Most of the determinants that govern its intracellular life cycle are controlled by the transcription factor PrfA, including the pore-forming cytolysin listeriolysin O (LLO), two phospholipases C (PlcA and PlcB), and ActA. We constructed a strain that lacked PrfA but expressed LLO from a PrfA-independent promoter, thereby allowing the bacteria to gain access to the host cytosol. This strain did not grow efficiently in wild-type macrophages but grew normally in macrophages that lacked ATG5, a component of the autophagy LC3 conjugation system. This strain colocalized more with the autophagy marker LC3 (42% ± 7%) at 2 h postinfection, which constituted a 5-fold increase over the colocalization exhibited by the wild-type strain (8% ± 6%). While mutants lacking the PrfA-dependent virulence factor PlcA, PlcB, or ActA grew normally, a double mutant lacking both PlcA and ActA failed to grow in wild-type macrophages and colocalized more with LC3 (38% ± 5%). Coexpression of LLO and PlcA in a PrfA-negative strain was sufficient to restore intracellular growth and decrease the colocalization of the bacteria with LC3. In a cell-free assay, purified PlcA protein blocked LC3 lipidation, a key step in early autophagosome biogenesis, presumably by preventing the formation of phosphatidylinositol 3-phosphate (PI3P). The results of this study showed that avoidance of autophagy byL. monocytogenesprimarily involves PlcA and ActA and that either one of these factors must be present forL. monocytogenesgrowth in macrophages.

High hydrostatic pressure effects on Listeria monocytogenes and L. innocua : Evidence for variability in inactivation behaviour and in resistance to pediocin bacHA-6111-2

2017 ◽  
Vol 64 ◽  
pp. 226-231 ◽  
Author(s):  
Carolina Bruschi ◽  
Norton Komora ◽  
Sónia Marília Castro ◽  
Jorge Saraiva ◽  
Vânia Borges Ferreira ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Pressure Effects

scholarly journals Nisin Resistance of Listeria monocytogenes Is Increased by Exposure to Salt Stress and Is Mediated via LiaR

2013 ◽  
Vol 79 (18) ◽  
pp. 5682-5688 ◽  
Author(s):  
Teresa M. Bergholz ◽  
Silin Tang ◽  
Martin Wiedmann ◽  
Kathryn J. Boor
Keyword(s):  
Salt Stress ◽  
Listeria Monocytogenes ◽  
Safety Concern ◽  
Response Regulator ◽  
Brain Heart Infusion ◽  
Control Measures ◽  
Protective Effects ◽  
Wild Type ◽  
Content Type ◽  
Type Strains

ABSTRACTGrowth ofListeria monocytogeneson refrigerated, ready-to-eat food is a significant food safety concern. Natural antimicrobials, such as nisin, can be used to control this pathogen on food, but little is known about how other food-related stresses may impact how the pathogen responds to these compounds. Prior work demonstrated that exposure ofL. monocytogenesto salt stress at 7°C led to increased expression of genes involved in nisin resistance, including the response regulatorliaR. We hypothesized that exposure to salt stress would increase subsequent resistance to nisin and that LiaR would contribute to increased nisin resistance. Isogenic deletion mutations inliaRwere constructed in 7 strains ofL. monocytogenes, and strains were exposed to 6% NaCl in brain heart infusion broth and then tested for resistance to nisin (2 mg/ml Nisaplin) at 7°C. For the wild-type strains, exposure to salt significantly increased subsequent nisin resistance (P< 0.0001) over innate levels of resistance. Compared to the salt-induced nisin resistance of wild-type strains, ΔliaRstrains were significantly more sensitive to nisin (P< 0.001), indicating that induction of LiaFSR led to cross-protection ofL. monocytogenesagainst subsequent inactivation by nisin. Transcript levels of LiaR-regulated genes were induced by salt stress, and lmo1746 andtelAwere found to contribute to LiaR-mediated salt-induced nisin resistance. These data suggest that environmental stresses similar to those on foods can influence the resistance ofL. monocytogenesto antimicrobials such as nisin, and potential cross-protective effects should be considered when selecting and applying control measures for this pathogen on ready-to-eat foods.

scholarly journals Alicyclobacillus acidoterrestris Strain Variability in the Inactivation Kinetics of Spores in Orange Juice by Temperature-Assisted High Hydrostatic Pressure

2020 ◽  
Vol 10 (21) ◽  
pp. 7542
Author(s):  
Patra Sourri ◽  
Anthoula A. Argyri ◽  
Efstathios Z. Panagou ◽  
George-John E. Nychas ◽  
Chrysoula C. Tassou
Keyword(s):  
High Pressure ◽  
Hydrostatic Pressure ◽  
Orange Juice ◽  
High Hydrostatic Pressure ◽  
Reference Strain ◽  
Wild Type Strain ◽  
Weibull Model ◽  
Inactivation Kinetics ◽  
High Pressure Level ◽  
Kinetics Of

In this work, the inactivation kinetics of Alicyclobacillus acidoterrestris spores by temperature-assisted high hydrostatic pressure was assessed by means of the Weibull model. Spores from two A. acidoterrestris strains (a wild-type strain and a reference strain) were inoculated in commercial orange juice and subjected to high pressure levels (500 and 600 MPa) combined with four temperature regimes (25, 45, 60 and 70 °C) for time up to 30 min. Results showed that for a given high-pressure level spore inactivation was higher as temperature progressively increased. Furthermore, the Weibull model consistently produced satisfactory fit to the inactivation data based on the values of the root mean squared error (RMSE < 0.54 log colony-forming units (CFU)/mL) and the coefficient of determination (R2 > 0.90 in most cases). The shape of inactivation curves was concave upward (p < 1) for all temperature/high pressure levels tested, indicating rapid inactivation of the sensitive cells of the bacterium whereas the remaining ones adapted to high hydrostatic pressure (HHP) treatment. The values of the shape (p) and scale (δ) parameters of the Weibull model were dependent on the applied temperature for a given high pressure level and they were further described in a secondary model using first-order fitting curves to provide predictions of the surviving spore population at 55 and 65 °C. Results revealed a systematic over-prediction for the wild-type strain regardless of temperature and high pressure applied, whereas for the reference strain under-prediction was evident after 3 log-cycles reduction of the surviving bacteria spores. Overall, the results obtained indicate that the effectiveness of high hydrostatic pressure against A. acidoterrestris spores is strain-dependent and also underline the need for temperature-assisted HPP for effective spore inactivation during orange juice processing.

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