Food Protection Trends - January/February 2020 - 12

TABLE 2. Indicator microorganisms on trolley handles*
Average** CFU/cm2

Standard deviation

Median CFU/cm2

Range CFU/cm2

1.25 × 102

4.43 × 102

9.0

1.8 - 1.89 × 103

Yeast and Molds

5.15

10.8

1.89

0.0 - 62.5

Enterobacteriaceae

2.72 × 104

6.9 × 104

0.19

0.19 - 1.9 × 105

Coliforms

2.71 × 106

6.9 × 106

0.19

0.10 - 1.9 × 107

27.73

70.5

0.00

0.00 - 1.99 × 102

Aerobic Plate Count

Escherichia coli

*Sample size n = 36.
** Value corresponds to the average of microbial concentration of each indicator microorganism, and the CFU/cm2 was estimated
based on the surface area of the trolley handle.
Aerobic Plate Count = APC; Yeast and Molds = YM; Enterobacteriaceae = EB; Coliforms = CF; Escherichia coli = EC.

TABLE 3. Indicator microorganisms on bottom of handheld baskets*
Average** CFU/cm2

Standard deviation

Median CFU/cm2

Range CFU/cm2

Aerobic Plate Count

1.07 × 102

95.9

73.6

11.63 - 2.8 × 102

Yeast and Molds

1.0 × 103

1.4 × 103

13.73

1.3 - 2.8 × 103

Enterobacteriaceae

4.67 × 103

1.1 × 104

1.05

0.03 - 2.8 × 104

Coliforms

3.52 × 105

9.4 × 105

0.70

0.06 - 2.8 × 106

5.07

11.6

0.07

0.00 - 42.04

Escherichia coli

*Sample size n = 25.
**Value corresponds to the average of microbial concentration of each indicator microorganism, and the CFU/cm2 was estimated
based on the surface area of the handheld basket's bottom.
Aerobic Plate Count = APC; Yeast and Molds = YM; Enterobacteriaceae = EB; Coliforms = CF; Escherichia coli = EC.

tested), but only 58% (56 samples out of 78 Staphylococcus
spp. positive) were confirmed S. aureus, of which the bottom
of handheld baskets had the highest level (96%, or 24 out
of 25 samples), followed by trolley handles (50%, or 18 out
36 samples), and trolley grills (39%, or 14 out 36 samples).
The overall prevalence of E. coli O157 was 6.3% (6 out 96
samples), which was found on all three surfaces. The bottom
of handheld baskets had the highest prevalence of this
pathogen, at 17% (4 out of 24 samples), followed by trolley
handles and trolley grills, each with 3% occurrence (1 out
of 36). Salmonella sp. was found on 7% of the samples (2
out of 96) and was detected on 16% of the handheld baskets
(4 out of 25 samples) and 8% of the trolley grills (3 out of
36 samples), but on none of the trolley handles sampled.
L. monocytogenes was not recovered from trolley grills and

12

Food Protection Trends January/February

handles, but was found on 17% of handheld basket bottoms
(4 out of 24 samples).
DISCUSSION
This study investigated food safety risk factors associated
with trolleys and supermarket handheld baskets. These
surfaces were tested for the presence and concentration
of indicator microorganisms and for the prevalence of the
most important foodborne pathogens relevant to public
health. Despite concern regarding bacterial contamination
of food from the supermarket environment (15, 21, 22),
little has been published with regard to surveillance of
specific food contact surfaces at the retail level. Supermarket
microbiological assessments are frequently performed
on food, but information is lacking about bacterial
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