Table 2.
EnABLe input parameters, distribution information, values, and sources of information for Listeria spp. growth, reduction, introduction and floor transmission.
| Symbol | Descriptiona | Equation/Distribution | Mean | 5th–95th percentile | Reference |
|---|---|---|---|---|---|
| p z | Probability that Listeria spp. is introduced into the room via objects from Zone 4 | 10Pert (−3.4, −2, −1.2, 4) | 0.01 | [0.002, 0.03] | expert opinion |
| N z | Amount of Listeria spp. introduced per object from Zone 4 (CFU) | 10Pert (0, 0.7, 2, 4.6) | 10 | [2, 27] | expert opinion |
| R d | Prevalence of Listeria spp. in cold-smoked salmon fillets on day d, for d = Monday, Tuesday, Wednesday, Thursday, Friday | 10Pert (−7, −4, −1, 4) | 10−4 | [10−5.9, 10−2.1] | expert opinion |
| N R | Concentration of Listeria spp. per contaminated cold-smoked salmon fillet (CFU/g) | Gamma (1.2, 0.19) | 6.3 | [0.5, 18] | 41 |
| α | Proportion of Listeria spp. transferred to an equipment surface upon contact with a contaminated cold-smoked salmon fillet | 10Normal (−0.28, 0.2) | 0.56 | [0.24, 1] | 50 |
| p r | Probability that a random event introduces Listeria spp. from outside the room | 10Pert (−3.4, −2, −1.2, 4) | 0.01 | [0.002, 0.03] | expert opinion |
| N r | Amount of Listeria spp. introduced per random event (CFU) | 10Pert (0, 2.7, 4, 5) | 1862 | [50, 6431] | expert opinion |
| K | Environmental carrying capacity of Listeria spp. (CFU/ml) | — | 108 | — | 51 |
| GT | Generation time (h) of Listeria spp. on environment surfaces (10 °C) | Uniform (8.4, 24.4) | 16.5 | [9.2, 23.6] | 46, 47, 52 |
| μ | Maximum specific growth rate (h−1) of Listeria spp. on environment surfaces (10 °C) | =In (2)/GT | 0.046 | [0.03, 0.075] | 51 |
| p t | Probability that contact on floor from foot and equipment traffic is sufficient to spread Listeria spp. to adjacent patch | Pert (0.03, 0.25, 0.65, 4) | 0.27 | [0.10, 0.48] | 49 |
| c i | Contact rate between the contaminated patch and the adjacent patch given the traffic level i = high, low, negligible | chigh = 60/patch/hr, clow = 12/patch/hr, cneg = 0.2/patch/hr | — | — | observed |
| p w | Probability that environmental Listeria spp. is transported to adjacent patches via (visible) water | Uniform (0.01, 0.05) | 0.03 | [0.012, 0.048] | assumed b |
| β | Transfer coefficient for Listeria spp. transmission among patches via traffic and water | Uniform (0.0, 0.05) | 0.025 | [0.002, 0.048] | assumed |
| p f | Probability that a cold-smoked salmon fillet falls to the floor during any given hour of production | Uniform (0.20, 0.40) | 0.30 | [0.20, 0.40] | observed |
| p c | Probability of a condensation transfer event given Listeria spp. is present | Uniform (0.01, 0.05) | 0.03 | [0.01, 0.05] | assumed |
| ηd | Log10 reduction of Listeria spp. from washing and sanitation on day d, for d=Monday, Tuesday, Wednesday, Thursday, Friday | Pert (−8, −6, −1.5, 4) | −5.6 | [−7.4, −3.5] | 17 |
| γ | Probability that a cleanable agent was not properly cleaned at the end of the shift | 0.01 | — | — | assumed |
aAll parameter values correspond to an hourly time-scale, the time-scale of the model.
bAssumptions were made when values were not available from literature or experts.