cross-contamination guidance learning lessons from the past · practices they know they should use...

Peter MidgleyFood Standards Agency

19 October 2011

Cross-contamination Guidance

Learning lessons from the past

E. coli O157 Cross contamination – key points

• Separation– No dual-use of complex equipment– Designated equipment

• Effective methods of disinfection• Effective hand washing technique• Appropriate corrective actions

E. coli O157 Cross contamination consultation

• Risk approach based on:Every consumer needs to be protectedfrom the risk of an isolated instance oflow level contamination of food by E.coli O157

Separation:• Designation and

maintenance of a microbiologically clean area

• Strong parallels with infection control

• Everything in the clean area must be a safe contact surface for hands, clothing and equipmentas well as food

Separation:• How does E. coli

O157 get from A (raw) to B (ready-to-eat)B

A

AA

A

A

A

A

Separation:• How does E. coli

O157 get from A (raw) to B (ready-to-eat)B

A

A

AA

A

A

Clean area

-Without control measures, you do not know where ‘A’ is

A

E. coli O157 Cross-contamination guidance - Supporting evidence

• Research carried out on behalf of the FSADetermining exposure assessment and modelling risks associated with the preparation of poultry products in institutional catering and the home, 2001 W. A. Harrison C. J. Griffith and D. Tennant.

• Observations and analysis at 50 catering establishments.• Key findings:

– All chicken was shown to have been adequately cooked– The average transfer rate of Campylobacter from raw chicken to surfaces

was 10% and the organism could still be recovered after touching eight consecutive surfaces.


• Key findings cont.– Percentage (%) of Campylobacter positive cooked chicken samples

obtained from institutional catering establishments after the preparation of chicken meals (n=10)


• Key findings cont.– Campylobacter contamination on cooked and ready-to-eat food

ingredients (excluding chicken) after the production of chicken meals within catering establishments (n=50)


• Key findings cont.– Campylobacter contamination occurred on various surfaces:Percentage (%) of surfaces contaminated with Campylobacter after the production of various chicken meals within catering establishments (n=50)

Bin lid

Hot tap

Cold tap

Sink

Draining board

Chopping board

Knife

Work surfaces

Chef’s cloth

Tongs

Refrigerator handle

Deep fat fryer handle


• Key findings cont.– The magnitude of surface contamination observed within catering

kitchens indicates that widespread contamination occurs during chicken meal preparation

• The most common route of transfer was from hands to an intermediate surface and then to another ready-to-eat food (e.g. side salad)

• Observational data confirmed that indirect cross contamination was an important factor that increased the risk of ingesting a contaminated meal.

• Hand washing and potential contamination of ready-to-eat food appeared to be the significant factors within catering food preparation


• Key findings cont.• The probability of specific food handling and preparation risks

occurring during catering food preparation included the following:– A 1 in 2.3 chance of failure to discard raw chicken packaging

immediately after use– A 1 in 5 chance of potential contamination of ready-to-eat

foods– A 1 in 12.5 chance of potential contamination of the cooked

meal– A 1 in 5 chance of adequate hand washing after handling raw

chicken or packaging


• Key findings cont.• Results of event tree modelling for three institutional

situations assuming 100% contamination of raw product and packaging.

Hotel Nursing Other institutionSum of positives 31% 9% 65%Sum of negatives 68% 89% 34%Total 99% 98% 100%Hand-to-mouth: 0% 0% 0%Inadequately cooked: 0% 0% 0%

Touch RTE: 5% 2% 10%Re-con RTE: 18% 4% 44%

Re-con cooked: 5% 2% 9%

Inadequate hand wash: 25% 8% 53%

Packaging not discarded: 19% 3% 25%


• Key findings cont.• Event tree analysis of roast chicken and grilled chicken in

catering establishments, assuming that all raw poultry and packaging is contaminated.

• When specific recipes were assessed, the probability of transfer ranged from 12% for roast chicken to 83% for grilled chicken.

CateringGrill Roast

Sum of positives = 83% 12%Sum of negatives = 15% 87%

Total 98% 99%Hand-to-mouth: 0% 0%

Inadequately cooked: 0% 0%Touch RTE: 17% 0%

Re-con RTE: 59% 7%Re-con cooked: 4% 5%

Inadequate hand wash: 75% 9%Packaging not discarded: 17% 5%


Research carried out on behalf of the FSAAssessing and Reducing the Risk of Cross Contamination of Food Stuffs in Food Handling Environments, Griffith, C.J., Davies, C., Breverton, J., Redmond, E.C. and Peters, A.C. (2002), Food Standards Agency, London.Examined multiple issues within a sample of 29 sites from 24 establishments - 14 manufacturing, 4 retailing and 11 food service(catering). • Although the sample was small it was considered if anything better

than average.• Majority of businesses had documented food policies with written

staff instructions. • Nearly all had cleaning schedules for high risk areas with staff

receiving training in cleaning and personal hygiene.• General beliefs about and attitudes towards

cross contamination and its prevention were positive.


• Key findings:• High incidence of cleaning and other equipment common to high

and low risk areas and high rates of transfer of cleaning and other equipment from low to high risk areas. Both could contribute to cross contamination

• Visual assessment was a poor indicator of cleanliness• Using microbiological tests 74% of food contact and 78% of

environmental surfaces were considered unclean• 82% of surfaces tested within 1 hour of cleaning were above

critical limits using microbiological tests.


• Hand contact surfaces were often above target microbiological values for clean surfaces and often highly contaminated:

– Tap Handles 96% unclean 27% > 12cfu/cm2

(equipment sinks)– Door Handles 77% unclean – Fridge Handles 97% unclean 20% >12cfu/cm2

– Telephones 66% unclean 28% >12cfu/cm2

– Soap Dispensers 80% unclean 6% >12cfu/cm2

• Food contact surfaces were also often above target values and often highly contaminated.

– Equipment / Utensils 77% unclean, 38% >12cfu/cm2

– Chopping Board 87% unclean 38% >12cfu/cm2

– Meat Blade 65% unclean 25% >12cfu/cm2

– Conveyor Belt, 77% unclean 40% >12cfu/cm2


• Laboratory experiments indicated once contaminated hands could still transfer bacteria onto a surface up to 5 touch- actions later. Clean hands could easily pick up bacteria from contaminated surfaces.

• Chains of food handling actions in food service were not as long, [as in manufacturing] however the risk of cross contamination was considered much higher with a much larger range of potentially contaminated objects touched. (90% of all actions involved 20 surfaces) Hands were the most frequent vehicle of cross contamination and handwashing was infrequently and poorly performed.

• The data indicate considerable potential for cross contamination during food handling activities and non-implementation of basic preventative measures.


• A greater effort needs to be made to minimise cross contamination and this should be centred around basic hygiene practices, i.e. effective handwashing and separation of areas and equipment (including cleaning) for raw and cooked foods.

• This will involve behavioural change on the part of some food handlers and not simply the provision of information.


• ... in-spite of training, food handlers often do not implement food safety practices they know they should use (Clayton et al 2002). Sufficient pathogens to cause illness must be transferred and subsequently survive, however even if pathogens were only involved in a small percentage of cases, the potential for cross contamination is considerable and is likely to be compounded within food service by:– meeting peak demands at meal times, – the failure to maintain handwashing facilities in food service

establishments (section 2.4.2) and – failure to separate high and low risk appropriately with the sharing of

common equipment (section 2.4.5)


As part of this work the authors drafted a code of practice that has many of the elements of the FSA's 2011 cross-contamination guidance. Some key extracts that should be familiar:• 3. Design premises to separate high and low risk activities. Eliminate,

or reduce, movement between the two areas as well as shared cleaning and food equipment and materials. Do not allow the sharing of common hand contact surfaces between the two. If high and low risk areas cannot be completely separated, ensure hands are properly washed and equipment disposed of or cleaned every time movement occurs.


Observation of food safety practices in catering using notational analysis, Deborah A. Clayton, Christopher J. Griffith, (2004); British Food Journal, Vol. 106 Iss: 3, pp.211 – 227• Observed 31,050 actions of 115 food handlers (across three

sessions) in 29 catering establishments using a notational analysis technique which allowed tracking of sequential events and was successful in identifying and recording a greater number of cross-contamination events than would have been highlighted using traditional approaches.

• The findings were conservative (i.e. additional faults may have occurred) because they only tracked one food handler so objects contaminated by others may have been undetected.

• All handlers had some form of training • 76% self-reported formal certificated food hygiene

training


• De-contamination actions were required on a large number of occasions due to the order of caterers' food preparation activities and the number of hand contacts with surfaces and equipment

• To improve standards of food hygiene in catering there is a need to minimise the requirements for de-contamination activities thereby reducing the potential for cross-contamination:

Clayton et al


Figure 2 demonstrates the mean number of times the specific food hygiene actions were required, attempted and carried out adequately per food handler across the three visits (270 actions).

Clayton et al


Assessment of Food Safety Practices of Food Service Food Handlers (Risk Assessment Data): Testing a Communication Intervention (Evaluation of Tools) Chapman, Benjamin; Eversley, Tiffany; Fillion, Katie; MacLaurin, Tanya; Powell, Douglas. Journal of Food Protection Volume 73, Number 6, June 2010 , pp. 1101-1107(7)• Observed practices of 47 food handlers using video cameras in ‘grill, deli,

and preparation’ areas at 8 sites of a North American food service company to establish the effectiveness of ‘info-sheets’ (348 h of data analysed). Each was observed on two days pre and two days post intervention.

• 11.3% of hand washing attempts were coded as correct• Indirect cross-contamination was found to be more prevalent than direct

cross-contamination.


“While there were improvements post–food safety infosheet introduction, the incidence of indirect cross-contamination followed the same pattern, increasing during traditional busy meal service times. From frequency of the evaluation of behaviors, direct cross-contamination made up less than 11% of total cross-contamination events, signifying that indirect cross-contamination events are much more likely to happen, and it highlights the complexity of the food service kitchen situation”

Chapman et al


• FIGURE 3. Mean indirect cross-contamination events per hour for all eight food service research observation sites (n ~ 47 food handlers).

Chapman et al


“While significant improvements were seen, a drastic improvement or elimination of risky behaviors was not seen”.

“Time of day, especially during busy times during traditional meal times of the food service operation, affected the food handling behaviors more than did the introduction of food safety infosheets. A recommendation could be the reengineering of some food service operational behaviors to reduce potential food safety risks quickly...”

“The prevalence of indirect cross-contamination seen throughout this study, [confirming Jay and colleagues 14] suggests that prevalence of cross-contamination is a hidden problem for food service, as food handlers acting in a multiuser environment may not see themselves as part of a team. Many of the recorded indirect cross-contamination events occurred when multiple food handlers used common food contact surfaces, utensils, or equipment.”

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