Food Protection Trends - May/June 2017 - 172

RESULTS
Reaction of unused sponges with disinfectants
All assays for residual chlorine and quat were done in
triplicate for each time point at which they were tested. The
average reduction of the disinfectants is shown in Table 2.
In 30 minutes of contact, the least of chlorine loss was with
the polyurethane sponge (0%) and the most by the cellulose
sponge (24%); however, quat reduction was similar with
both types of sponges.

from the two studies were pooled as for the development of the
dose response model in this study. The data that best fit a betaPoisson dose response curve (equation 3) were the coefficients
of = 0.1664 and a β =23,503, predicting the probability
of infection from ingestion with goodness of fit measure of
0.999998. N is the number of pathogenic E. coli ingested.
Probability (Infection) =1- (1 + N/β)-α

(3)

Sources of data for exposure parameters
To determine hand-to-mouth contacts per minute, data from
Nicas and Best (9) was utilized, using bootstrapping techniques
(8, 15). The developed hand-to-mouth contact distribution has
an average of 0.1332 per minute and a 95% confidence interval
of [0.0694, 0.2283]. To determine the area of mouth and hand,
raw data obtained from USEPA (14) and from Snyder et al.
(13) were utilized to generate the distributions, again, by use
of bootstrapping techniques. Area of mouth was on average
6.89 cm2, with a 95% Confidence Interval of [6.63, 7.13].
Area of hand distribution was on average 658 cm2, with a 95%
confidence interval of [533.1, 881.6].
A point estimate of 0.339 for transfer efficiency of E. coli
from hand to nose, hand to eye and hand to mouth was
used in the model, based on Rusin et al. (11), the only data
available in the literature. Parameters derived from the
bootstrapping are shown in Table 1.

Occurrence of bacteria in the sponges
Sponges were place in homes and the numbers of total
bacteria (HPC bacteria), coliform bacteria and E. coli were
monitored once per week over a four-week (28 day) period.
Table 3 shows the geometric means of the different types
of bacteria in the different types of sponges after 28 days.
Although a significant difference was not always seen in the
geometric average number of bacteria, numbers were always
lower in the polyurethane sponges than in the cellulose
sponges. Numbers of E. coli in the polyurethane sponges were
99.9% lower than in the cellulose sponges after 28 days. This
difference was statistically significant (P = 0.031). Numbers
of total bacteria in the polyurethane sponges were also
significantly lower.
The numbers of HPC bacteria in the antimicrobial
cellulose sponges were greater than in the regular sponges
after 28 days. The numbers of coliform bacteria and E. coli
were similar in both types of sponges. In a previous study,
we noted that a cellulose sponge with an antimicrobial claim
retarded the growth of only HPC bacteria, and the levels
after 7 days were similar in both regular and antimicrobial
cellulose sponges (4). Information was not provided by
the manufacturer on the nature of the antimicrobial in the
sponges used in this study.

Modeling probability of E. coli infection
E. coli usually enters the body through the mouth; hence
using parameters presented in Table 1 in equation 1, 2 and
3 yields equation 4, in which CSponge is the measured
concentration of E. coli found on the sponge:

Probability of infection from pathogenic E. coli
The probability of infection from the presence of

table 1. parameters for use with equation 1

Lower Limit

Upper Limit

Bootstrapping

533.1

881.6

658.94

13, 14

fraction

Point Estimate

0.0003

f2,Mouth

fraction

Point Estimate

0.339

AMouth

cm2

Bootstrapping

6.63

7.13

6.89

NMouth

per minute

Bootstrapping

0.0694

0.2283

0.1332

Parameter Unit

Distribution

AHand

cm2

172

95% Confidence Interval

Mean Value
Used in the
Model

Parameter

Food Protection Trends May/June

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Table of Contents for the Digital Edition of Food Protection Trends - May/June 2017