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 cells^a

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

^aThe detection threshold is set to 10³ cells ml⁻¹.

^bND, not determined.