Role of Microbiological Criteria and Value of Sampling

Transcription

1 Role of Microbiological Criteria and Value of Sampling Anna M Lammerding Public Health Agency of Canada Guelph, Ontario Canada

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3 Microbiological Criteria and Sampling Traditional definition and use Broadening the scope Thinking outside of the lot Fit for purpose If you do it Do it right Use it.

4 Microbiological Criterion: Traditional Definition The acceptability of a product or a food lot, based on the absence/presence or number of organisms including parasites, and/or quantity of their toxins/metabolites, per unit(s) of mass, volume, area or lot ICMSF, 1974, 1986; Codex Alimentarius Commission, 1997

5 Elements of a Microbiological Criterion (MC) A statement of the microorganism of concern and/or their toxins/metabolites and the reason for that concern The food to which the criterion applies The specific point(s) in the food chain where the MC should be applied Microbiological limits defining acceptable or reject

6 Elements of a Microbiological Criterion A sampling plan defining number and size of samples, method of sampling and handling The number and size of the analytical units to be tested The analytical methods to be used to detect or quantify The number of analytical units that should conform Any actions to be taken when criterion is not met

7 Different types of criteria Microbiological Standards Mandatory, written into law or regulations Acceptability of a food or compliance with a regulation or policy Defined by governments

8 Different types of criteria Microbiological Guidelines Advisory; acceptable or expected microbial levels when the food production process is under control Defined by governments or industry

9 Different types of criteria Microbiological Specifications Established between buyers and producers that define product quality and safety attributes for ingredients or finished product

10 Types of Microbiological Analyses Direct Analyses for specific pathogens Indirect Analyses for indicator microorganisms

11 Indicator organism A microorganism that is associated with a condition or state that impacts food safety for example - E. coli as an indicator of fecal contamination

12 Types of Microbiological Analyses Variables Sampling / Quantitative Determination of levels present Attribute Sampling Qualitative (Presence/absence) Quantitative results that have been grouped (e.g. < 10 cfu/g, cfu/g, >100c cfu/g)

13 Variables Microbial Testing Use with quantitative data when microbial history (distribution) is known and new results can be compared to see if statistically different Make full use of quantitative data

14 Two-Class (Presence/Absence) Attribute Sampling Plans Sampling plan definitions n: number of sample/analytical units examined per lot m: a microbiological limit (i.e. cfu/g); a sample is defined to be positive if its microbial content exceeds this limit c: maximum allowable number of sample units that can be positive and the lot is still acceptable; for pathogens, c is usually set to 0

15 Three-Class Attribute Sampling Plans Use with binned quantitative data wherein three levels defined Acceptable Marginally acceptable Unacceptable

16 Three-Class Attribute Sampling Plans n: number of sample units analyzed m: level below which sample unit is acceptable M: level wherein if any sample unit exceeds this value will result in the lot being rejected c: maximum number of marginally acceptable sample units above which the lot will be rejected

17 Frequency Distribution Describing Lot Quality mean s.d.: standard deviation (=0.8) Probability Density s.d. s.d Log cfu/g

18 0.6 Two-class sampling plan: m 0.5 Probability Density Proportion defective Log cfu/g

19 0.6 Three-class sampling plan: m M 0.5 Probability Density Proportion defective Log cfu/g

20 0.6 Three-class sampling plan: m M 0.5 Probability Density Proportion marginally acceptable Proportion defective Log cfu/g

21 ICMSF Cases Qualitative risk-based guidance for selection of samplings plans Statistically-valid for defined distributions 15 cases which reflect severity of the hazard, effect of handling/preparation on the hazard, and intended population

22 ICMSF Cases Type of hazard Conditions reduce hazard Conditions cause no change in hazard Conditions may increase hazard Utility Case 1 Case 2 Case 3 Indicator Case 4 Case 5 Case 6 Moderate Case 7 Case 8 Case 9 Serious Case 10 Case 11 Case 12 Severe Case 13 Case 14 Case 15

23 ICMSF Two-Class Plans: Mean CFU/G Rejected With 95% Probability m = 0 cfu / 25g, and standard deviation s.d. = 0.8 Case 10: n=5, c=0 1 cfu / 32g Case 11: n=10, c=0 1 cfu / 83g Case 12: n=20, c=0 1 cfu / 185g Case 13: n=15, c=0 1 cfu / 135g Case 14: n=30, c=0 1 cfu / 278g Case 15: n=60, c=0 1 cfu / 526g

24 To develop an effective MC need to know: The mean and distribution of the microorganism within the lot Definition of what is acceptable and what is not

25 m Log cfu/g Probability Density

26 m p a Log cfu/g Probability Density

27 m p a Log cfu/g Probability Density

28 m p a p d Log cfu/g Probability Density

29 m p a p d Log cfu/g Probability Density

30 m p a p d Log cfu/g Probability Density

31 m p a p d Log cfu/g Probability Density

32 m p a p d Log cfu/g Probability Density

33 m p d Log cfu/g Probability Density

34 m p d Log cfu/g Probability Density

35 End-product testing limited value The number of samples required becomes a limiting factor when the defect rate is small (<5%) Process control testing is more appropriate when verifying effectiveness of food safety systems

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37 Broadening the Definition of Microbiological Criteria In the past, MC have often been subjectively established without clear links to public health risk

38 New challenges new concepts new ways of thinking

39 Broadening the Definition of Microbiological Criteria New challenges: Very low levels and prevalence of pathogens limitations of methods to detect by ingredients or end product testing Global trade of foods -> low levels, low prevalence can result in widespread outbreaks Changing diets, different types of foods, challenges to testing product: fresh fruits and vegetables, sprouts

40 Broadening the Definition of Microbiological Criteria Introduction of risk analysis framework to microbial food safety, and new concepts in risk management, microbiological criteria have evolved to be components of an overall risk-based control system, to be implemented when useful and needed to achieve FSO, PO and Public Health Objectives

41 Microbiological Criteria Consider use to assess process/control measure(s), sampling & testing methods, take into account growth after the MC point ALOP (e.g. cases/yr) Raw Ingredients Pasteurization Storage Consumption Illness Process Criteria (e.g. deg C/min) Food Safety Objective (cfu/g, %)

42 Broadening the Definition of Microbiological Criteria MC need to be applied when and where they are most useful, and to generate results that inform risk managers in decision-making.

43 Examples of Microbiological Testing in Food Safety Management Acceptance Testing Lot inspection by government; test endproducts, attributes sampling plan for pathogens, indicators Verification of lots (batches) of known history, by government (end-products) or by industry (raw materials); attributes sampling plan for pathogens, indicators

44 Examples of Microbiological Testing in Food Safety Management Monitoring, checking CCP s, process lines by industry; test line samples with attributes or variables sampling plans for indicators Environmental sampling Line (contact surfaces), non-contact environment samples; used by industry, test residues, dust, water. Sampling plan targeted to find sources of contamination, efficacy of cleaning and disinfection

45 Examples of Microbiological Testing in Food Safety Management Verification Part of HACCP programs by industry, end product testing using attributes sampling plans, test for pathogens/indicators Surveillance Compliance surveys by governments/industry on products in commerce; attributes sampling plans (usually n = 1) test for pathogens

46 Examples of Microbiological Testing in Food Safety Management Investigation Testing anywhere along the food chain by governments or industry; all types of samples; investigational rarely statistically-based, may be biased sampling (targeted) based on prior knowledge Baseline studies must be statisticallybased

47 Elements of a Microbiological Criterion All valid considerations when thinking outside the lot Statistically-valid

48 Considerations for microbiological testing Evidence of actual or potential hazards to health The microbiological status of raw materials The effect of processing Likelihood and consequences of microbial contamination and/or growth during subsequent handling, storage and use

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50 Considerations The intended use of the food The category of consumers concerned The cost-benefit ratio associated with the application of the particular criterion

51 Food Protection Report, July/August 2001

52 Microbial Testing Effective use requires a clear understanding of the goals, assumptions, and characteristics of both the testing methods and the sampling plans

53 Method s s Operating Characteristics Lower Limit of Detection Repeatability Reproducibility Ruggedness Variance - Confidence Intervals

54 Codex Current Work Proposed Draft Guidelines for Control of Campylobacter and Salmonella spp. in Chicken Meat New approach for international trade guidelines Critical assessment of published data useful for these guidelines scientifically sound methods, sampling Poorly conducted studies not considered

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57 Controls GHP-based: Measures that are generally qualitative in nature and are based on empirical scientific knowledge and experience. Usually prescriptive and may vary between countries

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59 Controls Hazard-based: Measures that are developed from scientific knowledge of the likely level of control of a hazard have a quantitative base and can be validated obvious expectation of consumer protection but actual degree of protection unknown.

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61 Controls Risk-based: Measures developed from risk assessments or other information on risk (e.g. surveillance data), on the basis of specific knowledge of the likely level of consumer protection that will result quantitative base and can be validated against a level of consumer protection

62 Microbiological Testing & Sampling Essential for inspection Essential to verify hazards are controlled Valuable for environmental monitoring Useful to detect defective batches CANNOT guarantee 100% safety Quality control cannot be based on endproduct testing only Risk assessment

63 Microbiological Testing & Sampling The classical ICMSF cases and sampling schemes still offer a risk-based approach for examining lots for regulatory or trade purposes The statistical basis for ICMSF cases can be applied for other types of sampling programs

64 ????

65 Make Use of the Data! Microbiological data collection is resource intensive Define purpose will the data (and efforts) help make better risk management decisions? Make sure the data collection process is statistically sound, appropriate methods to sample and test Microbiological data that is not analysed, not used to inform decision-making - serves no purpose! If you collect it, use it!

66 References ICMSF Microorganisms in Foods. 7. Microbiological Testing in Food Safety Management (2002) Microorganismos de los alimentos. 7. Análisis microbiológico en la gestion de la seguridad alimentaria (2004)

67 Coming Soon!!

68 Someday, they will get it right! In memory of, and tributes to, Susanne Dahms ( ) Profesora (Berlin, Germany); Statistician; ICMSF Member ( ); speaker at 1st ABRAPA meeting in SP (2002); an adventurer, scientist, artist, traveller, teacher too short her life with us.