cross contamination transfer dynamics at retail: mock deli renee r. boyer, phd virginia tech...
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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
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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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