Food Protection Trends - May/June 2020 - 150

graduate students, 43 were staff, four were undergraduate
students, and five were "other." Three participants answered
that they were not affiliated with the University of Arkansas.
It was also noted whether or not the participant had a
protective case and/or a screen cover on their TMD. Of 100
participants, 82 had a protective case, and 28 had a screen
cover. When asked about their TMD usage frequency,
85% of participants indicated that they check their TMD
at least once an hour, and 35% stated that they check their
TMD more than three times per hour. Participants were
also asked several questions about their perceptions of
cleaning practices for single-user TMDs and the perceived
contamination risks associated with single-user TMDs
within food service establishments. Table 1 indicates
that, based on a mean response of > 4, most participants
believe that (i) TMDs can harbor harmful microorganisms;
(ii) food service workers should clean their TMD; and
(iii) using a TMD while working with food is a potential
health risk. Conversely, participants were not completely
convinced that requiring food service employees to clean
their TMD would reduce potential transmission of harmful
pathogens, with a mean response of 3.78 (Table 1).
Characterization of bacteria on TMDs
The results from the bacteria recovery revealed that
every TMD was contaminated with bacteria, with a greater
prevalence of Gram-positive bacteria than of Gramnegative bacteria. Most of the colonies tested were Grampositive and were reduced by both cleaning interventions.
Gram-positive bacteria represented 94.5% of bacteria on
both side A and B of the TMDs; this is likely due to the
Gram-positive nature of the human epidermis microbiota
(16). The baseline bacterial concentration on Side A was
0.76 log10 (CFU/cm2+1), with no significant difference
between the treatment groups (P = 0.183). A comparison

of the bacterial concentration on the TMDs revealed a
statistically significant difference (P < 0.0001) between
bacterial concentrations on Side A and Side B regardless of
the treatment type, at 0.76 and 0.43 log10 (CFU/cm2+1)
difference, respectively (Fig. 2). There was no difference (P
= 0.644) in bacterial concentrations on Side B by treatment
type. Moreover, there was no significant difference (P =
0.132) in mean log reductions between treatment groups,
with 0.28 and 0.38 log10 (CFU/cm2+1) for dry microfiber
cloths and IA wipes, respectively.
Microbial concentration and TMD use
A comparison of the participant's role at the University
of Arkansas with the log10 (CFU/cm2+1) bacteria on
their TMDs revealed that there was no statistically
significant difference in bacterial concentrations among
the roles. There was also no statistically significant
difference in bacterial concentrations among frequency
of use categories. Participants were also asked about
their TMD cleaning habits; there was no statistically
significant difference between bacterial concentrations
and self-reported frequency of cleaning (Table 2). Various
cleaning methods for TMDs were reported, including
tissues, moist cloths, "my shirt," and lens cleaning wipes.
Most participants (n = 82) had a protective case on
their TMD, and a smaller number (n = 28) had a screen
cover. Comparing the mean log10 reductions revealed no
significant difference in log10 reduction by treatment with
respect to the presence or absence of a protective case or
screen cover (data not shown).
DISCUSSION
Microbial contamination of TMDs has been reported
previously, such as in a study by Egert et al. in which a
similar population was investigated (5). Specifically, the

TABLE 1. Responses to survey questions on TMD cleaning and health risks in general and
in retail food service establishments
Survey Question

5-point Likert Scalea
Mean Response (± SD)

Is it important for food service employees to regularly clean their TMD?

4.39 (0.82)

Are there health risks associated with using TMDs while working with food?

4.23 (0.93)

Can TMDs become contaminated with harmful germs that can make you sick?

4.36 (0.72)

If there were requirements for food service employees to clean TMDs, would the
potential for transmission of harmful germs via contaminated TMDs decrease?

3.78 (0.89)

definitely not = 1, probably not = 2, might or might not = 3, probably yes = 4, definitely yes = 5
SD = standard deviation.
a

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