Scientific Publications - Work Done by Microbiology Reader Bioscreen C

A. Metris, S. Georges, M. Peck, J. Baranyi, Effect of sodium chloride and pH on the distribution of the lag times of individual cells of Listeria innocua, Young Scientists Meeting, John Innes Centre, Norwich Research Park, Colney, Norwich, UK, 2001, Abstracts, 1 p.

ABSTRACT

While the growth rate of pathogens in food can commonly be predicted as a function of the environmental factors, the lag time is difficult to model. Because of low infectious doses of pathogens, such as Escherichia coli O157:H7, stochastic models are more useful than deterministic models to describe the lag time within a population. It is well-known that both the environmental conditions and the history of the cells (e.g. heat or acid stress) influence the lag. In this study, the lag time distribution of individual Listeria innocua has been studied using automated turbidometric measurements (Bioscreen; Labsystems, Basingstoke, UK). The experiments were based on the principle that the distribution of the lag times should be reflected by the distribution of the detection times of the turbidity of the wells. The effect of different growth conditions, characterised by pH and NaCl concentrations, have been investigated while the inoculum was always prepared in the same conditions (same history). Gamma distributions were used to describe the lag time distributions. It was found that the more hostile the conditions for the microorganisms, the higher the mean and the more spread the distributions were.

(Abstract online)

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Last modified: May 25, 2005