Abstract
The dynamic response of pathogens to environmental changes depends on the behaviour of individual cells within the population. Exposure of L. monocytogenes to different stress conditions has been shown to result in selection of a variety of stable resistant variants. This population diversity allows for growth and survival of the population under a wide range of
environmental conditions with specific fitness and robustness parameters considered a trade-off; a variant may have an advantage under one condition, while this might be a disadvantage under other conditions. Therefore, the types of variants and their relative contributions within the WT population will depend on the environmental conditions encountered by the population. This
study aims to evaluate the effect of environmental conditions on the composition of the L. monocytogenes populations and how dynamic conditions affect the fraction of stress resistant variants within the population. Growth parameters were obtained for WT and a set of eight acid resistant L. monocytogenes variants. A gamma model was used to estimate the growth behaviour under combined mild stress conditions (temperature, water activity and pH). Also a set of inactivation parameters was determined (heat and acid). This set of robustness and fitness parameters of WT and variants was used to model their performance in simulated food chains. Predictions were validated by qPCR in which WT and variant were distinguished from each other by specific primers, designed on an rpsU mutation in the variant. With this method, a variant fraction as low as 10-5 could be identified correctly in a WT population. This study provided more insight in the conditions which can select for variants, which is an important step in control of these stress resistant subpopulations in industrial settings. It also highlights the potential persistence of stress resistant variants in food processing environments and
consequential impact on food safety.
environmental conditions with specific fitness and robustness parameters considered a trade-off; a variant may have an advantage under one condition, while this might be a disadvantage under other conditions. Therefore, the types of variants and their relative contributions within the WT population will depend on the environmental conditions encountered by the population. This
study aims to evaluate the effect of environmental conditions on the composition of the L. monocytogenes populations and how dynamic conditions affect the fraction of stress resistant variants within the population. Growth parameters were obtained for WT and a set of eight acid resistant L. monocytogenes variants. A gamma model was used to estimate the growth behaviour under combined mild stress conditions (temperature, water activity and pH). Also a set of inactivation parameters was determined (heat and acid). This set of robustness and fitness parameters of WT and variants was used to model their performance in simulated food chains. Predictions were validated by qPCR in which WT and variant were distinguished from each other by specific primers, designed on an rpsU mutation in the variant. With this method, a variant fraction as low as 10-5 could be identified correctly in a WT population. This study provided more insight in the conditions which can select for variants, which is an important step in control of these stress resistant subpopulations in industrial settings. It also highlights the potential persistence of stress resistant variants in food processing environments and
consequential impact on food safety.
| Original language | English |
|---|---|
| Publication status | Published - 2015 |
| Event | ICPMF9, International Conference on Predictive Modelling in Food, Rio de Janeiro (Brazil) - Rio de Janeiro, Brazil Duration: 8 Sep 2015 → 12 Sep 2015 |
Conference
| Conference | ICPMF9, International Conference on Predictive Modelling in Food, Rio de Janeiro (Brazil) |
|---|---|
| Country/Territory | Brazil |
| City | Rio de Janeiro |
| Period | 8/09/15 → 12/09/15 |