a clearer path for pathogen testing

A CLEARER PATHFOR PATHOGEN TESTING

HOSTBill McDowellEditorial Director, Meatingplace

MODERATORTom JohnstonEditor, Meatingplace

WHAT IS ACHIEVABLE IN PATHOGEN TESTING?

Gary R. Acuff Professor, Food Microbiology

Head, Department of Animal Science

Poll Question

What is really achievable in pathogen reduction?1. It depends upon how much contamination is present. 2. 3 Logs. 3. A scientific endpoint is needed. 4. Complete elimination of pathogens.

Pathogens▶ Enterohemorrhagic Escherichia coli

▶O157:H7▶Non-O157

▶ Salmonella▶ Campylobacter?▶ Focus on EHECs

Source▶ Cattle

▶Gastrointestinal tract▶Anything in close proximity to feces

▶Hide▶Hooves▶Dust▶Water

Control Opportunities▶ Genomics▶ Livestock production & feedlot

▶Handling and well-being issues▶ Slaughter▶ Fabrication▶ Retail▶ Consumer, foodservice

Control Opportunities▶ Genomics▶ Livestock production & feedlot

▶Handling and well-being issues▶ Slaughter▶ Fabrication▶ Retail▶ Consumer, foodservice

Where are the hazards most effectively addressed?

Control Opportunities▶ Genomics▶ Livestock production & feedlot

▶Handling and well-being issues▶ Slaughter▶ Fabrication▶ Retail▶ Consumer, foodservice

Where are the hazards most effectively addressed?

Consumer Education

Carcass Interventions

TemperatureChemical

Laboratory Challenge►Parallel evaluations►Marker pathogens in fecal material►Salmonella serotype Typhimurium►Escherichia coli O157:H7►Non-inoculated fecal material►Indicator organisms

Feces Fecesplus

Pathogens

Log Reduction of E. coli O157:H7 and S. Typhimurium on Beef Carcass Surfaces

Log Reduction of E. coli O157:H7 and Coliforms on Beef Carcass Surfaces

What Is Realistic?

► Elimination?► Reduction?► The real issue: What remains?► And where is it?

Trimming and grinding processes will distribute

any remaining pathogens.

Unfortunate Event▶ Adulterant declaration

▶ Well-intended (possibly), but short-sighted▶ “Zero” doesn’t exist in bacterial enumeration▶ Unintended consequence - difficult to measure

improvement or control

What is really achievable?

1. Does it really matter?2. It all has to be gone. 3. Attempt to achieve what is required.4. Absence is unreasonable (impossible,

illogical, unscientific, other favorite adjective).

An Endpoint is Needed► How can one

aim for a target that does not exist?

► Or one that constantly changes?

Food Safety Objective

▶ The maximum frequency and/or concentration of a hazard in a food at the time of consumption that provides or contributes to the appropriate level of protection.

Food Safety Objective

▶ H0 - ∑R + ∑I ≤ FSO▶ FSO = Food Safety Objective▶ H0 = Initial level of the hazard▶ ∑R = Total (cumulative) reduction of the hazard▶ ∑I = Total (cumulative) increase of the hazard

▶ FSO, H0, R and I are expressed in log10 units

Food Safety ObjectiveH0 - ∑R + ∑I ≤ FSO3 - ∑R + 0 ≤ -

23 - ∑R ≤ -2

∑R ≤ -5

∑R ≥ 5

5-Log ReductionH0 - ∑R + ∑I ≤ FSO3 - ∑R + 0 ≤ -

23 - ∑R ≤ -2

∑R ≤ -5

∑R ≥ 5

104

103

102

101

100

10-1

10-2

10-3

10-4

Reduction of E. coli O157:H7 and S. Typhimurium on Beef Surfaces by Sequential Pre- and Post-chill Lactic Acid Sprays

Microbiological Testing▶ In the absence of an FSO, it is

necessary to establish default criteria.

▶ “Safe Harbor”

Microbiological Testing

▶Where are we going?▶ Is there an end?▶ Is more sampling the answer?

Microbiological Testing

▶ In the ICMSF scheme for managing risk, two uses for criteria are identified...

1.To validate that control measures meet performance criteria

2.To determine acceptability when no more effective means of providing assurance is available (i.e., in the absence of knowledge that HACCP has been properly applied)

Microbiological Testing

▶ In the ICMSF scheme for managing risk, two uses for criteria are identified...

1.To validate that control measures meet performance criteria

2.To determine acceptability when no more effective means of providing assurance is available (i.e., in the absence of knowledge that HACCP has been properly applied)

If there is a way out, this may be it.

Poll Question Results

What is Really Achievable in Pathogen Reduction?1. It depends upon how much contamination is present. 2. 3 Logs. 3. A scientific endpoint is needed. 4. Complete elimination of pathogens.

Provide a scientific endpoint and the industry will achieve

the necessary reduction.

Food Safety

Risk Reduction. Tools that provide trusted data for making informed decisions.

Operational Efficiency. Reduce overtime and downtime - increase productivity.

Competitive Edge.Solutions that create a powerful brand and impact your bottom line.

At every step, 3M Food Safety is dedicated to protecting your brand and improving your productivity.

www.3M.com/foodsafety/MMW

CURRENT BEEF INDUSTRY SAMPLING AND TESTING

PROGRAMS FOR E coli O157:H7

Timothy P. BielaEVP Food Safety & Quality

AFA Foods

Poll Question

Which best describes your position? Packer

ProcessorOther

Are you currently testing the following products for E coli O157?Trim YES or NOGround Beef YES or NO

What are we doing and why?

• Carcass Testing– USDA Mandated carcass testing

• Boneless Beef Trim Testing– N60 Sampling and Testing– Sub-lot size varies from 1 to 5 combo bins

• Raw Ground Beef Testing– Commercial versus Retail Testing Programs

Food Safety Verification for O157

• Verification of HACCP and Food Safety Program for control of Enteric Pathogens– Must define the sublot– Must define the sample size and frequency of

sampling– Must define the actions to be taken in the event of

a positive result

Total-N60 Platform“The Food Safety Umbrella”

Sample units of n=60 per ‘lot’ provides robust statistical basis. Statistical confidence of N60 testing is at least 95.0% probability that ECH7 will be

detected if present [assuming a population prevalence rate of 5.0% or higher]. Surface Slice vs SubSurface Tissue

Surface Area – N60 examines substantially more total surface area of external surface tissue vs other trim or final-grind sampling methods.

Dilution Effect – Thin surface slices vs ‘sterile’ underlying tissue or ground meat gives increased probability of detection. 5X more sensitive than finished ground beef sampling.

Lab method sensitivity – capable of detecting 15 cfu/375g, 100% of the time. 1:5 enrichment media [vs 1:10 standard] improves sensitivity. PCR-BAX initial screening using ‘modified-enhanced’ methodologies provides

+90% accuracy.

This slide courtesy of “others”. For Example only.

N60 Sampling• 60 individual samples are taken from the lot• Preference is to sample surface material• Samples should be taken randomly across the

entire “stream” or population of meat• Various sizes are used; 1x3, 2x5, etc….• Lot sample size must be a minimum of 375 g• The entire sample should be analyzed

References

• Beef Industry Food Safety Council Best Practices– http://bifsco.org/harvest.aspx

• USDA FSIS– http://origin-www.fsis.usda.gov/PDF/Draft_Guidelines_Sampling_Beef_Trimmings_Ecoli.pdf

• International Commission on Microbiological Specifications for Foods (ICMSF)– http://www.icmsf.iit.edu/publications/sampling_plans.html

Microbiological Testing Programs must have:• A robust sampling plan that is designed to meet the

microbiological testing objectives with a high degree of confidence.

• The adequacy of the sampling plan should be evaluated by an independent third party.

• In order to ensure the interpretability of testing results, the sampling plan must be implemented correctly.

• Based on the results of microbiological testing, actions must be taken. (Plan / Do / Check / Act)

Key Elements of Sampling Plans• Define what constitutes a sample, • Define the number of samples to be collected, • Define how samples will be collected, • Define the number of samples it will collect, • Define the frequency of sample collection,• Define the procedures used to analyze samples and, • Define the criteria for signaling an out-of-control

process

Key Elements of Sampling Plans (2)

• Ensure that samples collected are representative of the entire population; minimize bias,

• Ensure that the sample size is sufficient to provide the desired level of confidence.

• Ensure the sampling plan addresses the fact that pathogens are heterogeneously distributed

• Ensure that sampling considers the variability in prevalence rates over time (seasonal variation).

Food Safety Verification for O157Example #1

• Major Retailer w Grinding Operation:– One sample every two hours of production.– Samples are analyzed with PCR/DNA.– Positive products are diverted to further

processing.– Positives are bracketed from one hour in front of

first positive to end of the day.– Positive rates range from .4 to .7%.

Food Safety Verification for O157Example #2

• Major Integrated Fed Beef Packer– Format varies from one sample per hour to one

sample every fifteen minutes to screening pre-ground products prior to packaging.

– Samples are analyzed with PCR/DNA.– Positives are bracketed from one hour in front of

first positive to one behind and subjected to intensified sampling.

– Positive rates range from .4 to .7%.

Food Safety Verification for O157Example #3

• Major Quick Service Restaurant– One sample taken for every batch of ground beef

formulated.– Samples are composited for four batches.– Composites are sampled and a 25 gram analyte is

tested.– Positives are bracketed from one hour in front of

first positive to end of the day.– Positive rates have ranged from 0 to .2%.

HACCP and Risk Assessment for Raw Ground Beef Products

• Retail versus Commercial Ground Beef– Retail• Consumers; Families• No identified platform for cooking• No verification of cooking controls

– Commercial• Quick Serve and Casual Dining• Specific platforms for cooking and controls

Commercial Testing Event Summary Example

Commercial Testing Event Summary Example (2)

SummarySampling and testing for pathogens is difficult. The key

to an effective microbiological testing program is the sampling plan. Since it is not possible to conduct 100% testing, one must use a sample to draw inferences about the entire population. As indicated in the draft USDA Compliance Guideline, the sampling plan should be designed to provide a high probability of finding E. coli O157:H7, if it is present, and identifying a process that is out of control.

Summary (2)• Due to the heterogeneous distribution of pathogens in meat

products, microbiological testing cannot guarantee that product is free of contamination and should not be used for product acceptance.

• Microbiological testing should be used to verify process control and should occur on an ongoing basis as part of the “Plan-Do-Check-Act” cycle.

• Consistent and uniform sampling and testing methodologies for microbiological testing of beef manufacturing trimmings should be developed and implemented with the primary objective of protecting public health.

• N60 sampling should be the minimum sampling protocol for beef manufacturing trimmings in all federally inspected meat and poultry establishments.

Poll Question Results

Are you currently testing trim or raw ground beef products for E coli O157?Trim YES or NOGround Beef YES or NOPacker YES or NOProcessor YES or No

Ted BrownSenior Food ScientistCargill R&D Center

BUILDING THE LABORATORY RELATIONSHIP

POLL QUESTION

Lateral flow users: are you using a lateral flow or antigen/antibody based test that is specific for E. coli O157:H7?

• Yes• No

Discussion Focus

• Methodology Selection• Laboratory / Establishment Relationship

Before you Decide that Testing is necessary and on a Methodology

Remember: Testing is a PART of a Food Safety System

People:

Knowledgeable &

Skilled

Processes & Programs

Monitoring & Verification

Investment

Food Safety System

60NRC July 14, 2010

Monitoring & Verification

LottingWhat does the

sample represent?

SamplingHow will the

sample be collected?

AnalysisWhat target will

be analyzed?

Decision Making

What decisions will be made based on the

data?

Methodology

General Indicators (APC)

Generic E. coli

Shiga toxin producing E. coli

E. coli O157

E.coli O157:H7

DNA typing

PROGRAM ACTIONWhat will you do with the results?

Good, bad, or ugly?

Test Methodology Options

24h

Confirmed or Not Confirmed?

8h

18h

72h

1:9

1:5

1:1

• Gold Standard• > Time to results 72h to

Negative• High skill• Stopping point defines

reported result• O157:H7• O157Cultural

• Less skill• Typically target O157• Further testing is

necessary for O157:H7• > enrichment times than

DNA based methodsAntigen

• Medium skill• Typically target O157:H7• Some kits may be O157

specific• < time to result

DNA

Basis for Method Selection…

Test Result Application

Approvals

Business Based Considerations

Fit For Use

Test Method Application

• Will the method provide the information needed to support my program objectives?

• Do you know if the reported result for your method is O157 or O157:H7 or something entirely different?

Approvals

• Methods should be evaluated by an independent body

• Not all approvals are created equal

• Approval alone should not be the basis to make a method selection

Business Based Considerations

• Goal is to find the target bug

• This is not just a price based decision

• This is an organization/business specific question with specific organization/business based answers

Fit for Use• Do I have the right tool

for the job?– Is my method validated for

the matrix as I am going to use it• Analytical unit size• Enrichment/Incubation• Detection limit

• Are there any variations from the method as it was validated compared to my use?

Laboratory RelationshipIs not: Only About

Cost Data

Inquisition

Is:Investment

Trust, Confidence and

EngagementMutual

understanding of Fit for use

• Testing is a PART of a Food Safety System.

• Not all methods are created equal: O157 positive result, does not mean that it is O157:H7 specifically

• Who or what will the results effect? What will you do with the results? Good, bad, or Ugly?

• Method must be fit for use when selected and as used

• A lab relationship is an investment

A CLEARER PATHFOR PATHOGEN TESTING

POLL QUESTION RESULTS

Lateral flow users: are you using a lateral flow or antigen/antibody based test that is specific for E. coli O157:H7?

• Yes• No

QUESTIONS & ANSWERS

FOR MORE INFORMATION:

Gary Acuff: gacuff@tamu.eduTimothy Biela: tbiela@amerfood.comTed Brown: Ted_Brown@cargill.com

3M: Christine Aleski ,Global Marketing Development Manager email: cmaleski@mmm.com

Bill McDowell: bmcdowell@meatingplace.comTom Johnston: tjohnston@meatingplace.com

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