Article Figures & Data
Figures
- FIG. 1.
Plots of single-cell growth probability (a) and of means of single-cell lag times (b) of L. monocytogenes in 1/2FB at 30°C versus the percentages of injury resulting from BAC (1), nitrite (2), starvation (3), HCl (4), freezing (5), peracetic acid (6), phenol (7), NaOH (8), acetic acid (9), NaCl (10), lactic acid (11), and heat (12) stresses.
- FIG. 2.
Plot of single-cell growth probability in 1/2FB at 30°C versus the loss of cultivability on TSAye for Listeria monocytogenes strains INRA101 (1), ADQP101 (2), UNIR100 (3), LM14 (4), Scott A (5), and EGDe (6) after starvation stress (a) and osmotic stress (b). Points and error bars represent the means and standard deviations of parameters for replicated experiments, respectively.
- FIG. 3.
Proportions of Listeria monocytogenes cells able to initiate growth, after a stress with low impact, the starvation stress (black bars), or after one with high impact (white bars)—BAC stress (a), heat stress (b), or osmotic stress (c)—in 1/2FB at 30°C supplemented with microflora and/or food components to simulate the enrichment phase of fermented meat product (a) and core of red-smear soft cheese (b) and to study the effect of wild microflora isolated from various food samples and multiplying in 1/2FB (c). Error bars represent the between-experiment standard deviations.
- FIG. 4.
Observed cumulative distributions (•) of single-cell lag times of Listeria monocytogenes in 1/2FB at 30°C with fitted EVIIb distributions (solid lines) and best-fitting distributions other than EVIIb (dashed lines for lognormal [LN] or Weibull [Weib] distributions). Cells were previously stressed by BAC (a), nitrite (b), starvation (c), HCl (d), freezing (e), peracetic acid (f), phenol (g), NaOH (h), acetic acid (i), NaCl (j), and lactic acid (k). x axes show τi (h); y axes show cumulative distribution function.
- FIG. 5.
Relationship between means and standard deviations of the single-cell lag times of Listeria monocytogenes. Shown are data obtained in this study in 1/2FB at 30°C and calculated from the EVIIb parameter values (•) and data obtained by Guillier and Augustin (22) (▪) for 54 different physiological states, growth conditions, and strains in TSBye. The solid line is the major axis regression line. (Adapted from reference 22 with permission from Elsevier.)
- FIG. 6.
Plot of means of single-cell lag times versus the single-cell growth probability of Listeria monocytogenes in 1/2FB at 30°C resulting from BAC (1), nitrite (2), starvation (3), HCl (4), freezing (5), peracetic acid (6), phenol (7), NaOH (8), acetic acid (9), NaCl (10), lactic acid (11), and heat (12) stresses.
Tables
- TABLE 1.
Probability of detecting 25-g food samples as positive for Listeria monocytogenes after an enrichment phase in 1/2FB at 30°C according to the initial contamination, the enrichment length, and the physiological state of contaminating cellsa
Stress encountered p Mean of τ (h) Probability according to level of food contamination (in 25 g) and length of enrichment 25 CFU 5 CFU 1 CFU 16 h 24 h 16 h 24 h 16 h 24 h Exponential growth phase 1 0 1 1 1 1 1 1 Acetic acid (pH 4.2, 25°C, 24 h) 0.92 6.2 1 1 0.81 1 0.19 0.85 Starvation (25°C, 24 h) 0.91 2.3 1 1 1 1 0.80 0.91 Nitrite (200 ppm, 25°C, 52 h) 0.87 2.3 1 1 1 1 0.77 0.87 Lactic acid (pH 4.2, 25°C, 24 h) 0.52 9.6 0.69 1 0.12 0.92 0.02 0.39 Freezing (−20°C, 48 h) 0.42 3.6 1 1 0.81 0.93 0.27 0.42 HCl (pH 3, 25°C, 34 min) 0.39 2.6 1 1 0.86 0.91 0.32 0.39 Phenol (2.3 ppm, 25°C, 48 h) 0.27 4.3 0.99 1 0.52 0.78 0.13 0.26 NaCl (25%, 30°C, 48 h) 0.24 7.9 0.59 1 0.12 0.68 0.02 0.21 NaOH (pH 12, 25°C, 25 min) 0.15 5.7 0.73 0.98 0.19 0.54 0.04 0.14 BAC (10 mg liter−1, 25°C, 12 min) 0.11 1.5 0.94 0.94 0.43 0.44 0.11 0.11 Heat (55°C, 2.5 min) 0.05 NDb Peracetic acid (200 ppm, 25°C, 15 min) 0.05 4.4 0.47 0.72 0.11 0.22 0.02 0.05
