Table 1.
Parameters and their distribution used in exposure assessment.
| a. Transfer of E. coli to and between fomites. | ||||||
| E. coli Concentration on Primary Surface (Fomite) | Transfer to Secondary Surface | |||||
| Primary Surface | Input Values (Range) a | Distribution | Secondary Surface | Input Values (range) a | Distribution | Source(s) |
| (log10 CFU/sq. cm) | (%) | |||||
| Meat Preparation Surfaces | ||||||
| Cutting board b | 5.80 | Uniform | Cutting board-to-meat | 32.57 | Normal | [21] |
| (high dose) | (5.54, 6.06) | (high dose) | (0.86, 93.41) | |||
| Cutting board | 3.73 | Uniform | Cutting board-to-meat | 55.91 | Normal | [21] |
| (low dose) | (3.63, 3.82) | (low dose) | (23.17, 97.31) | |||
| Knife c | 6.08 | Uniform | Knife-to-meat | 37.98 | Normal | [21] |
| (high dose) | (6.01, 6.15) | (high dose) | (24.15, 37.98) | |||
| Knife | 4.21 | Uniform | Knife-to-meat | 50.42 | Normal | [21] |
| (low dose) | (3.53, 4.89) | (low dose) | (12.82, 109.64) | |||
| Meat | 6.23 | Uniform | Meat-to-cutting board | 53.01 | Normal | [21] |
| (high dose) | (6.06, 6.39) | (high dose) | (42.03, 74.18) | |||
| Meat | 4.33 | Uniform | Meat-to-cutting board | 62.94 | Normal | [21] |
| (low dose) | (3.69, 4.97) | (low dose) | (34.28, 89.75) | |||
| Meat | 6.33 | Uniform | Meat-to-knife | 49.09 | Normal | [21] |
| (high dose) | (6.15, 6.5) | (high dose) | (37.75, 49.09) | |||
| Meat | 4.03 | Uniform | Meat-to-knife | 56.17 | Normal | [21] |
| (low dose) | (3.87, 4.18) | (low dose) | (21.86, 105.69) | |||
| Typical Kitchen Surfaces | ||||||
| Countertop d | 2.36 | Triangular | [22] | |||
| (0.78, 3.00) | ||||||
| Hand towel | 1.79 | Triangular | [23] | |||
| (0.13, 3.86) | ||||||
| Dish cloth | 1.75 | Triangular | [24] | |||
| (0.12, 4.25) | ||||||
| Kitchen sponge | 4.00 | Triangular | [25] | |||
| (3.00, 6.00) | ||||||
| b. Transfer from fomites to fingertip. | ||||||
| Input Values (Range) a | Distribution | Source(s) | ||||
| (%) | ||||||
| Meat-to-fingertip e | 34.31 | Lognormal | [26] | |||
| (34.31, 166.37) | ||||||
| Cutting board-to-fingertip | 53.3 | Triangular | [27] | |||
| (30.40, 98.00) | ||||||
| Knife-to-fingertip | 54.1 | Triangular | [27] | |||
| (29.40, 99.00) | ||||||
| Countertop-to-fingertip | 36.5 | Triangular | [27] | |||
| (0.30, 100.00) | ||||||
| Hand towel-to-fingertip f | 13.4 | Triangular | [27] | |||
| (2.60, 33.30) | ||||||
| Dish cloth-to-fingertip f | 13.4 | Triangular | [27] | |||
| (2.60, 33.30) | ||||||
| Kitchen sponge-to-fingertip | 13.4 | Triangular | [27] | |||
| (2.60, 33.30) | ||||||
| c. Bacterial survival after hand washing and transfer to lip. | ||||||
| Input Values (range) a | Distribution | Source(s) | ||||
| (%) | ||||||
| Survival of E. coli on hand after control wash | 13.49 | Normal | g | |||
| (5.04, 36.06) | ||||||
| Survival of E. coli on hand after wash with antimicrobial #1 | 1.12 | Normal | g | |||
| (0.16, 7.80) | ||||||
| Survival of E. coli on hand after wash with antimicrobial #2 | 0.72 | Normal | g | |||
| (0.04, 11.96) | ||||||
| Transfer from fingertip-to-lip | 28.6 | Lognormal | [28] | |||
| (28.60, 63.07) | ||||||
a = For uniform distribution, mean (low, high) values are presented. For normal distribution, mean (5%, 95%) values are presented. For lognormal distribution, mean (mean, standard deviation) values are presented. For triangular distribution, likeliest (minimum, maximum) values are presented. b = Input values measured for HDPE were used. c = Input values measured for stainless steel were used. d = Input values measured for granite were used. e = Enterobacter aerogenes B199A was used as a surrogate microorganism. f = Input values measured for 100% cotton were used. g = Original data described in Methods Section 2.1. The input values given in Table 1 were used in Monte Carlo simulation. This was a single-touch scenario. Survival of E. coli at the fingertip was estimated under four scenarios: No hand washing, washing with a control (non-antimicrobial) bar soap, and washing with two different antimicrobial bars designated #1 and #2. Note that the study did not consider the natural growth or decay of E. coli, the timeframe of the contact, or the frequency of touching.