The effect of sublethal injury by heating, freezing, drying and gamma‐radiation on the duration of the lag phase of <i>Salmonella typhimurium</i>

Mackey, B.M.; Derrick, Christine M.

doi:10.1111/j.1365-2672.1982.tb04683.x

Cited by 115 publications

(71 citation statements)

References 27 publications

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“…However, when the stress was not lethal, the cells could adapt and subsequently grow in the new condition. Other similar studies (14,18) have also reported that in sublethally stressful environments, cell populations suffer an initial loss and then may recover.…”

Section: Discussionmentioning

confidence: 87%

Lag Phase of Salmonella enterica under Osmotic Stress Conditions

Zhou

George

Métris

et al. 2011

Appl Environ Microbiol

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Salmonella enterica serovar Typhimurium was grown at salt concentrations ranging from 0.5 to 7.5% in minimal medium with and without added osmoprotectant and in a rich medium. In minimal medium, the cells showed an initial decline period, and consequently the definition of the lag time of the resultant log count curve was revised. The model of Baranyi and Roberts (Int. J. Food Microbiol. 23:277-294, 1994) was modified to take into account the initial decline period, based on the assumption that the log count curve of the total population was the sum of a dying and a surviving-then-growing subpopulation. The lag time was defined as the lag of the surviving subpopulation. It was modeled by means of a parameter quantifying the biochemical work the surviving cells carry out during this phase, the "work to be done." The logarithms of the maximum specific growth rates as a function of the water activity in the three media differed only by additive constants, which gave a theoretical basis for bias factors characterizing the relationships between different media. Models for the lag and the "work to be done" as a function of the water activity showed similar properties, but in rich medium above 5% salt concentrations, the data showed a maximum for this work. An accurate description of the lag time is important to avoid food wastage, which is an issue of increasing significance in the food industry, while maintaining food safety standards.Salmonella enterica causes severe enteritis in both humans and animals (19,25). Human infection usually results from eating contaminated food, such as poultry, milk, beef, eggs, pork, and seafood (13); consequently, monitoring and control of contamination by Salmonella are necessary and important in the food industry.One way of controlling Salmonella in food is to add salt to decrease the water activity and inhibit microbial growth. However, the effect of salt highly depends on the presence of osmoprotectants, which have been shown to affect the growth rate (7). The immediate response of cells to osmotic stress is to accumulate K ϩ and glutamine to maintain a viable turgor of the cell. These potentially harmful substrates are then replaced by compatible solutes, such as proline, trehalose, and glycine betaine, to stimulate growth (11). The compatible solutes either can be taken up from the growth medium if available or, if none are present, need to be synthesized de novo by the cell. Betaine (also known as glycine betaine or trimethylglycine) is one of the most common and effective osmolytes utilized by Salmonella spp. Although betaine cannot be synthesized by Salmonella enterica serovar Typhimurium, it can be transported from the growth medium under high external osmolality conditions (8). In the absence of osmoprotectants in the environment, trehalose is thought to be the main osmoprotectant synthesized by Escherichia coli and Salmonella.Predictive microbiology has become a main tool to describe the growth of microorganisms in recent years. Predictive models concentrate mainly on the ...

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Section: Discussionmentioning

confidence: 87%

Lag Phase of Salmonella enterica under Osmotic Stress Conditions

Zhou

George

Métris

et al. 2011

Appl Environ Microbiol

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“…The proportion of sublethally damaged cells is determined by the difference on counts between cells recovered in a non-selective media and a selective media after the treatment. The selective media more commonly used to detect the membrane damage is agar with sodium chloride added (Mackey & Derrick, 1982). Fig.…”

Section: Membrane Damage Of Salmonella Typhimurium and S Aureus Cellmentioning

confidence: 99%

Inactivation of Salmonella Typhimurium and Staphylococcus aureus by pulsed electric fields in liquid whole egg

Monfort

Gayán

Saldaña

et al. 2010

Innovative Food Science & Emerging Technologies

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“…4), discrepancies between predicted growth regions and observed growth curves were found for initial bacterial concentrations of 10 2 and 10 0 CFU ⅐ ml Ϫ1 . The change from an inoculum of approximately 10 2 CFU ⅐ ml Ϫ1 maintained at 30°C for 14 h to an inoculum of about 1 CFU ⅐ ml Ϫ1 starved for 840 h at 30°C led to an increase in lag time from 32.6 to 66.6 h. The extension of lag phase with physical injury of cells has been frequently reported (14,17,21,22), and models describing the effect of heat injury on subsequent lag period have been published for L. monocytogenes (6,7,23). Albertson et al…”

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confidence: 98%

Significance of Inoculum Size in the Lag Time of Listeria monocytogenes

Augustin

Brouillaud-Delattre

Rosso

et al. 2000

Appl Environ Microbiol

105

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The lag time of Listeria monocytogenes growing under suboptimal conditions (low nutrient concentrations, pH 6, and 6.5°C) was extended when the inoculum was severely stressed by starvation and the inoculum size was very small. Predictive microbiology should deal with bacterial stress and stochastic approaches to improve its value for the agro-food industry.In predictive microbiology, it is commonly assumed that inoculum size has no effect on subsequent microbial growth, and some studies (8, 9, 10) have confirmed this for growth of Listeria monocytogenes. However, Gay et al. (12) observed that inoculum size could have an effect on the duration of the lag phase of L. monocytogenes under particular conditions simulating soft cheese ripening. This observation could challenge the validity of predictive models because growth modelling is usually done with initial concentrations of bacteria higher than 10 3 CFU ⅐ ml Ϫ1 , even though foods are usually contaminated with lower numbers of cells.It has been shown with other bacteria, like Bacillus (19), Achromobacter delmarvae, Micrococcus luteus (see reference 16 for review), and Salmonella (26), that the duration of the lag phase depends inversely on the size of the inoculum. This phenomenon was observed only under a restricted range of conditions, for example, in poor but not in rich media, with starved cells (16), or with heat-injured cells (26). The aim of this work was to study the effect of inoculum size on the lag phase of L. monocytogenes growing in a poor medium, i.e., broth, containing only 1 g of Bacto Peptone (Difco Laboratories, Detroit, Mich.) per liter plus 0.85% sodium chloride (Prolabo, Paris, France) (TS), under suboptimal conditions: pH 6 and 6.5°C and with cells stressed by starvation.L. monocytogenes Scott A maintained on tryptone-soya agar (Oxoid, Unipath, Ltd., Basingstoke, Hampshire, England) at 4°C was subcultured onto tryptone-soya agar (Oxoid) plus 0.6% yeast extract (AES, Combourg, France) (TSYE) at 37°C for 24 h, and five colonies were transferred into TSYE broth and incubated at 30°C for 24 h. This culture was used to inoculate TSYE broth to prepare inocula at 30°C. The change in viable count of L. monocytogenes in TSYE broth at 30°C determined on nonselective TSYE agar and selective Palcam (Oxoid) agar is shown in Fig. 1. The percentage of injured cells was determined by differential counts on selective and nonselective media (24). Inocula were prepared at 30°C for 14, 160, and 840 h to obtain cells in late log phase, early stationary phase after a decrease in cell viability of 96.8% viable cells and 35% injured cells and late stationary phase with a loss of viability of 99.9% and 21% injured cells (Fig.

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The effect of sublethal injury by heating, freezing, drying and gamma‐radiation on the duration of the lag phase of Salmonella typhimurium

Cited by 115 publications

References 27 publications

Lag Phase of Salmonella enterica under Osmotic Stress Conditions

Lag Phase of Salmonella enterica under Osmotic Stress Conditions

Inactivation of Salmonella Typhimurium and Staphylococcus aureus by pulsed electric fields in liquid whole egg

Significance of Inoculum Size in the Lag Time of Listeria monocytogenes

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