Cross Contamination Transfer Dynamics at Retail: Mock Deli

Renee R. Boyer, PhD

Virginia Tech

Interagency Risk Assessment - L. monocytogenes in Retail Delicatessens Public Meeting

Washington, DC - May 22nd, 2013

Objective• To identify significant cross contamination pathways in a retail deli

that occur when contamination is introduced from different sites

• Using an abiotic surrogate, GloGerm™ lotion

• Study was funded by FSIS to provide data for the risk assessment

• Results have been published in peer reviewed journal:Maitland, J., R. Boyer, D. Gallagher, S. Duncan, N. Bauer, J. Kause and J. Eifert. 2013. Tracking cross contamination transfer dynamics at a mock retail deli using GloGerm. Journal of Food Protection. 76(2):272-282.

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Layout of Mock Deli:

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Materials and Methods:• In each experimental trial:

– one of six locations was contaminated (20ml GloGerm™)• Deli slicer blade

• Floor drain

• Surface of deli meat chub

• Employees bare hands

• Employees gloved hands

• Preparation table surface

– A series of standard deli operations was performed (~10 min)– Photographs of all contaminated surfaces were taken– Sensory panel was trained to quantify contamination

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Deli Operations (performed in this order):

Adapted from Lubran et al. 2010. Observational study of food safety practicesIn retail deli departments. J. Food Prot. 73:1849-1857.

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• A trained sensory panel was used to quantify presence and level of contamination– Coverage: the total area containing GloGerm™– Intensity: the brightness of the GloGerm™

Material and Methods:

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Ex. photograph of slicer shelf (the angled surface used to hold the meat chub level and steady before coming in contact with the blade) analyzed by the 8 panelists

compared to control photograph (clean, no contamination ).

In this photograph GloGermTM contamination was initiated on the slicer blade. Eight panelists’s ranked photo 460 as having heavy contamination (2.75±0.46).

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Materials and Methods: • Panelists were asked to rank:

– Contaminated surfaces compared to clean surface– Controls: initial inoculum levels; surfaces after cleaning;

duplicate photos

• The one word rankings were converted to numbers

none = 0, slight = 1, moderate = 2, heavy = 3• A mean contamination score was determined and then

translated back into a descriptive value (rounded)

Ex. 2.75 = heavy; 2.25 = moderate

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Effect of starting contamination point on “overall spread”

Recipient of Contamination

Source of Contamination: Descriptive, Numerical

Floor Drain Gloves Blade Meat Chub Prep Table Hands

Floor Drain see next slide none0.00±0.00a

none0.00±0.00a

none0.00±0.00a

none0.00±0.00a

none0.00±0.00a

Gloves none0.00±0.00a

heavy3.00±0.00c

slight1.49±0.73b

moderate2.06±0.57c

heavy2.81±0.40c

heavy2.94±0.25c

Blade none0.00±0.00a

slight0.63±0.50b

heavy3.00±0.00d

slight1.00±0.00b

none0.00±0.00a

none0.00±0.00a

Meat Chub slight0.94±0.25a

heavy2.50±0.52c

moderate2.13±0.62c

heavy3.00±0.00d

slight1.25±0.45ab

moderate1.69±0.70b

Prep Table none0.13±0.34a

moderate1.88±0.34c

moderate1.75±0.45c

moderate1.88±0.45c

heavy3.00±0.00d

slight1.00±0.00b

Door Handle none0.38±0.50a

heavy3.00±0.00c

slight1.25±0.68b

none0.38±0.50a

moderate2.31±0.70b

none0.13±0.34a

Within a row, means w/ different letters are significantly different based on nonparametric Behrens-Fisher test, P < 0.05.

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Spread of contamination on the floor:

(Key: ♦-slight, ♦♦-moderate, ♦♦♦-heavy, -floor drain)

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Additional locations contaminated:Recipient of Contamination

Source of Contamination Floor Drain Gloves Blade Meat Chub Prep Table Hands

Hand wash sink faucet knobs

0 3 0 0 0 1

Top of glove box

0 3 0 0 0 3

Cart handles 0 2 0 0 0 0

Scale face 0 2 1 0 0 0

Surface of interior deli case shelf

0 0 2 3 0 0

Bottom of prep table sink, near drain.

0 0 0 2 3 0

Slicer table near slicer

0 0 1 1 0 0

Bottom of employee shoes

3 0 0 0 0 0

Cart Wheels 3 0 0 0 0 0

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Transfer of contamination to meat slices (third and ninth sliced consecutively)

1Values within rows followed by the different letters are significantly different (based on the Behrens-Fisher test P < 0.05)

Slice Number

Source of Contamination: Descriptive3, Numerical (mean±st. dev.)

Floor Drain Gloves Blade Meat Chub Prep Table Hands

3 none0.38±0.52a

moderate2.38±0.74c

heavy3.00±0.00d

heavy3.00±0.00d

slight1.25±0.46b

slight0.63±0.52a

9 none 0.25±0.46a

Slight1.38±0.52b

heavy3.00±0.00c

slight 1.38±0.74b

moderate 1.50±0.53b

slight1.13±0.35b

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Effect of starting contamination point on spread throughout the slicer:

Recipient of Contamination

Source of Contamination: Descriptive2, Numerical3

Floor Drain Gloves Blade Meat Chub Prep Table Hands

Blade none0.00±0.00a

slight0.63±0.50b

heavy3.00±0.00c

slight1.00±0.00b

none0.00±0.00a

none0.00±0.00a

Bed none0.43±0.51a

slight0.50±0.52a

slight1.38±0.50a

moderate2.13±0.81c

slight1.13±0.34b

slight1.31±0.48b

Shelf none0.00±0.00a

slight1.19±0.40c

slight0.88±0.34b

heavy2.88±0.34d

slight0.63±0.50b

slight0.88±0.34b

Handle none0.38±0.50a

heavy2.88±0.50c

slight1.25±0.45b

heavy2.75±0.45c

heavy3.00±0.00c

slight1.25±0.45b

Carriage none0.00±0.00a

heavy2.88±0.34e

moderate1.75±0.68c

slight1.00±0.52b

moderate2.13±0.62d

slight1.13±0.34bc

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Conclusions• Six originating sites were also generally the six most

commonly contaminated from other surfaces– However, no contamination seen spread to the floor– Contamination spread to deli case door handle

• Highest degree of spread was from contaminated gloves

• Future research– Running similar trials with a mixture of fluorescing material and

pathogen (or a biotic surrogate)

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