Inactivation Kinetics of Three Listeria monocytogenes Strains under High Hydrostatic Pressure

Boeijen, Ineke K. H. Van; Moezelaar, Roy; Abee, Tjakko; Zwietering, M.H.

doi:10.4315/0362-028x-71.10.2007

Cited by 51 publications

(53 citation statements)

References 27 publications

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“…Previous research showed that heterogeneity in L. monocytogenes populations (strains EGDe, LO28, and Scott A) affects resistance to high hydrostatic pressure (HHP). Inactivation of such heterogeneous populations resulted in survival curves with significant tailing, indicating the presence of an HHP-sensitive and an HHP-resistant fraction (32). Analysis of the cells that survived such HHP treatments revealed that the higher resistance of LO28 (32) and Scott A (17, 18) was a stable feature for part of the resistant fraction.…”

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confidence: 99%

“…Inactivation of such heterogeneous populations resulted in survival curves with significant tailing, indicating the presence of an HHP-sensitive and an HHP-resistant fraction (32). Analysis of the cells that survived such HHP treatments revealed that the higher resistance of LO28 (32) and Scott A (17, 18) was a stable feature for part of the resistant fraction. Contrary to these results, no stable HHP-resistant isolates were obtained for EGDe (32).…”

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“…Analysis of the cells that survived such HHP treatments revealed that the higher resistance of LO28 (32) and Scott A (17, 18) was a stable feature for part of the resistant fraction. Contrary to these results, no stable HHP-resistant isolates were obtained for EGDe (32). A significant fraction of the stably resistant variants of both Scott A and LO28 had an altered ctsR gene.…”

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confidence: 99%

“…HHP inactivation was performed as described previously by Van Boeijen et al (32). Cell suspensions were subjected to 350 MPa at 20°C in ACES.…”

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“…Therefore, the initial number of variants was calculated from the fraction of variants that survived HHP and by extrapolation of this fraction's survival curve, as follows: (2) where N t,var equals the number of variants (log CFU/ml) at time t (min) and D var the fitted decimal reduction time or D-value (min) of the HHP-inactivated variants (31,32). The inactivation data were fitted with an appropriate model.…”

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

Boeijen

Francke

Moezelaar

et al. 2011

Appl Environ Microbiol

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Stable high-hydrostatic-pressure (HHP)-resistant Listeria monocytogenes LO28 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 their ctsR genes. For the variants whose ctsR genes 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-resistant L. monocytogenes variants.Listeria monocytogenes can cause listeriosis in animal and human populations. Human listeriosis is a rare but severe disease and is one of the leading causes of death among patients with food-borne diseases in the United States. The estimated annual rate of invasive listeriosis in the United States is 3 cases and for countries within the European Union is 2 to 10 cases per million people per year (33). Recently, several European countries experienced an apparent increase in the incidence of listeriosis (13).A specific characteristic of L. monocytogenes that appears to be critical to its ability to cause human food-borne illness is its capacity to survive under harsh conditions. The occurrence of variants and the generation of population heterogeneity are factors that may contribute to the survival capacity of L. monocytogenes. Previous research showed that heterogeneity in L. monocytogenes populations (strains EGDe, LO28, and Scott A) affects resistance to high hydrostatic pressure (HHP). Inactivation of such heterogeneous populations resulted in survival curves with significant tailing, indicating the presence of an HHP-sensitive and an HHP-resistant fraction (32). Analysis of the cells that survived such HHP treatments revealed that the higher resistance of LO28 (32) and Scott A (17, 18) was a stable feature for part of the resistant fraction. Contrary to these results, no stable HHP-resistant isolates were obtained for EGDe (32). A significant fraction of the stably resistant variants of both Scott A and LO28 had an altered ctsR gene. This gene encodes CtsR, a DNA binding protein that regulates class III heat shock genes (7). The observed alterations in ctsR resulted not only in increased resistance to high pressure but also in increas...

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“…HHP inactivation was performed as described previously by Van Boeijen et al (32). Cell suspensions were subjected to 350 MPa at 20°C in ACES.…”

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confidence: 99%

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confidence: 99%