Pathogen reduction dialogue panel 3 indicators surrogates vs pathogens
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Pathogen Reduction Dialogue Panel 3 Indicators/Surrogates vs. Pathogens. Frank F. Busta Professor Emeritus, University of Minnesota 7 May 2002. Classic Definitions. Index Organism - microorganism or group of microorganisms that is indicative of a specific pathogen

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Pathogen reduction dialogue panel 3 indicators surrogates vs pathogens l.jpg
Pathogen Reduction DialoguePanel 3Indicators/Surrogates vs. Pathogens

Frank F. Busta

Professor Emeritus, University of Minnesota

7 May 2002

INSTITUTE OF FOOD TECHNOLOGISTS


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Classic Definitions

  • Index Organism - microorganism or group of microorganisms that is indicative of a specific pathogen

  • Indicator organism - microorganism or group of microorganisms that are indicative that a food has been exposed to conditions that pose an increased risk that the food may be contaminated with a pathogen or held under conditions conducive for pathogen growth

    (Buchanan 2000)

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What is indicated

  • Positive test for indicator organism

    • does NOT necessarily indicate the presence of pathogen

  • Detection of index organism

    • points to the occurrence of a related pathogen

  • A marker can function both as an index and an indicator organism

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Other Names

  • Model organisms

  • Sentinel organisms

  • Surrogate organisms

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Some Preferred Qualities of Ideal Indicators

  • History of presence or absence in foods ~ pathogen/or toxin

  • Microbial metabolites present initially/or after growth ~ pathogen

  • Growth of indicator = target microorganism under all conditions

  • Easily detectable, quantifiable, distinguishable, preferably rapid

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Indicators

  • Specific microorganism

    • viable colony count, enrichment culture, indirect cell count

  • Metabolite

    • lactic acid titration

  • DNA fragment

    • PCR

  • Indirect measure

    • ATP

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Traditional Requirements for Indicator of Food Safety

  • Easily and rapidly detectable

  • Easily distinguishable from food flora

  • History of association with pathogen

  • Present with pathogen

  • Numbers correlate with pathogen

  • Growth requirements/rate equal to pathogen

  • Die off rate parallels pathogen

  • Absent from food free of pathogen

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Examples of Proposed or Adopted Indicator Organisms

  • Enterobacteriaceae

    • Includes collectively to coliform, fecal coliform, E. coli

  • Coliform*

  • Fecal Coliform*

  • Escherichia coli*

  • Enterococci

  • Bifidobacterium

  • Coliphages

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Enterobacteriaceae

  • Facultative anaerobes, G(-) bacilli, mesophilic, ferment gluc  acid, cat +

    • (some psychotroph, e.g. Enterobacter)

  • Citrobacter, Enterobacter, Escherichia, Klebsiella,Salmonella, and others

  • Recommended over coliforms to better assess gluc+, lac- members of food flora

    • (i.e. Salmonella)

  • Problem: Not confined to intestinal tract

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Coliforms

  • Defined by phenotype NOT genotype

  • G(-), asporogeneous rods, ferment lactose  acid & gas within 48h @ 35°C and produce dark colonies with a metallic sheen on Endo agar

  • Consist of 4 genera:Citrobacter,Enterobacter, Escherichia and Klebsiella

  • E. coli most indicative of fecal pollution

    • E. coli typeI ( IMViC ++--)

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Fecal Coliforms

  • Coliforms ferment lactose  acid & gas within 48h @ 44.5-45.5°C

  • Strains recovered: E. coli, K. pneumoniae, Enterobacter spp., C. freundii

  • Originally used to assess fecal contamination in water

  • E. coli O157:H7 does not grow well at 44.5 °C

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E. coli

  • For use to determine sanitary significance: must comply with coliform & fecal coliform definitions

  • Type I IMViC ++--

  • Type II IMViC -+--

  • Some strains are neither Type I or II

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E. coli

  • Regarded as most valuable indicator of fecal contamination of raw foods

  • Not a reliable indicator of fecal contamination in processed foods

    • Grows in environment

    • Indicator of inadequate processing

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Indicator groups that may be or are considered pathogens

  • Enterobacteriaceae

    • Includes collectively to coliform, fecal coliform, E. coli

  • Coliform*

  • Fecal Coliform*

  • Escherichia coli*

  • Enterococci

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Issues/Use of Coliforms & Fecal Coliforms

  • May contain non-enteric members (e.g. Serratia, Aeromonas)

  • Indicator of inadequate sanitation of equipment

  • Indicator of inadequate heat-processing /post-pasteurization contamination of RTE foods

  • Non-enteric fecal coliforms

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Limitations of Pathogens as Indicator Organisms

  • Concentrations may be very low and difficult to relate

  • May not compete well with food flora

  • Presence may not relate to another pathogen

  • Presence may initiate regulatory action – may be considered adulteration

  • Pathogens require special laboratory skills

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Advantages Pathogens May Have as Indicator Organisms

  • Easily and rapidly detectable

  • Easily distinguishable from food flora

  • Association with another pathogen

  • Present concurrently with another pathogen

  • Numbers correlate with another pathogen

  • Growth requirements/rate equal to another pathogen

  • Die off rate parallels other pathogen

  • Common source with other pathogen

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Performance Standards

  • Intended to effectuate decrease in pathogen with goal to improve public health

  • Fecal contamination is major source of enteric pathogens

  • May use microorganisms classified as indicator/index organisms

  • Pathogen could be used if it meets criteria

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Indicator in lieu of specific pathogen: Basic Criteria

  • Similar survival & growth

  • Common source

  • Direct relationship between condition influencing pathogen presence & indicator

  • Practical methods

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Performance Standards

  • E. coli as an indicator/index?

  • Salmonellae as an indicator?

  • Enterobacteriaceaeas an indicator/index?

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Ideal/Index Indicator

  • Present & rapidly detectable in foods of interest

  • History of association/present with pathogen

  • Presence and concentrations correlate with pathogen

  • Easy to detect/enumerate,and distinguishable

  • Growth requirements/rate, and die-off rate equal to pathogen

  • Not affected by other food components or microflora

  • Resistant to injury from stress of processing

  • Non-hazardous to testing personnel

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Current Status For Indicator/Index Microorganisms

  • Indicator and Index organisms used forcompliance with the GMPs, hygienic processing and handling of food

  • E. coli Biotype I and coliforms most common

  • Stipulated in regulations (e.g.PMO, EPA drinking water standards)

  • Vendor agreement for procuring ingredients and raw materials

  • Quality assurance, Audits

  • Specific pathogens and toxin assays available

  • Usefulness of the concept being revisited

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Surrogate

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Surrogate

Microorganism or representative material that serves as an alternate for target pathogen in studies evaluating or validating control or intervention processes such as chemical or physical decontamination procedures.

  • Generally taxonomically, physiologically and ecologically related to pathogens or other target microorganisms

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Surrogate Criteria - 1

  • Non-pathogenic

  • Inactivation characteristics those of target

  • Durability similar to target

  • Stable surrogate characteristics

  • High concentrations easily prepared

  • Stable between preparation and use

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Surrogate Criteria - 2

  • Easily enumerated

  • Easily differentiated

  • Inactivation kinetics consistent with target

  • Genetically stable

  • Will not establish as spoilage problem

  • Resistant to sub-lethal injury or reversibility

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Summary & Conclusions

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Summary & Conclusions

  • In use for over 100 years in some situations

  • Effective with extensive validation and qualifications.

  • Currently no well-established relationship of indicator with the occurrence of emerging water and foodborne pathogens

  • Direct, sensitive and specific tests for detection and enumeration of target pathogens/metabolites are available

  • Indirect association of markers with food safety and quality may not be reliable for “due diligence”

  • May become increasingly useful with new analytical methods

  • Challenge : selection and validation of appropriate indicator/surrogate

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Research Needs and Opportunities

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Research Needs and Opportunities

  • Identify indicators to determine exposure to conditions permitting contamination or survival/growth of pathogen after decontamination

  • Identify surrogate microorganisms for use in specific situations to measure effectiveness of intervention decontamination treatments

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Research Needs and Opportunities

  • Develop comprehensive standardized and validated protocols for use with surrogate microorganisms in testing efficacy of pathogen control

  • Propose, design, and test evaluation program(s) by systematically assessing possible sources of contamination, number of foodborne outbreaks attributed to the product/category, potential for mishandling, incidence data, and other quantifiable measures.

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Research Needs and Opportunities

  • Identify and validate approaches to test the elected indicator(s) against wild and laboratory culture strains in well-controlled pilot plant environments and in open natural commercial conditions

  • Develop appropriate analytical tools for indicator(s)

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Research Needs and Opportunities

  • Collect new survey data with emerging molecular technologies that accurately discriminate between virulent and non-virulent strains

  • Identify or develop methodology to quantitatively retrieve indicators, especially when a stress may result in damaged or VNC organisms.

  • Assess existing and new testing procedures and sampling plans to verify appropriate stringency with stipulated statistical design

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Research Needs and Opportunities

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