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Year 4 Public Health > Microbiological Criteria > Flashcards

Microbiological Criteria Flashcards

1
Q

What is a microbiological criterion?

A

A criterion defining the acceptability of a product, a batch of foodstuffs or a process, based on the absence, presence or number of microorganiisms and/or on the quantity of their toxins/metabolites, per units of mass, volume, area or batch

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2
Q

What is the difference between microbiological criterion and food safety objective/performance objectives?

A

FSOs and POs which only represent limits and MC consists of several aspects:
* microoragnisms of concern have to be stated
* A qualititive or quantitative analytical method validated and chosd to give a sufficienctly reliable estimate
* critical limits based on data appropriate to the food
* Sampling plan inclusing the sampling and decision criteria for a lot

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3
Q

What are the two different types of microbiological criteria in the EU?

A

Food safety criteria
Process hygiene criteria

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4
Q

What is food safety criteria?

A

Criterion defining the acceptability of a product or a batch of foodstuff applicable to the products places on the market
Defined only for the pathogens/foodstuffs with efficienct contribution to public health

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5
Q

What is process hygiene criteria?

A

Criterion indicating the acceptable functioning of the production process
Sets an indicative contamination value which corrective actions are required

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6
Q

Why do we need microbiological criteria?

A
  • Useful for validation and verification of HACCP based on process and procedurees, and other hygiene control measures
  • Assess the acceptability of a batch of food
  • Communicate the level of hazard control
  • Offers some assurance
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7
Q

What is wrong with non-destructive methods of sampling?

A

recovery rate of bacteria is not 100%

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8
Q

Microbiological criteria cannot be applied without microbiological testing
What can testing be used for?

A
  • Acceptance of a lot of raw materials, food ingridients or end products
  • Shelf life of foods
  • Monitoring production lines
  • Monitoring hygienic status of the processing environment
  • verification of GHP and HACCP
  • Baseline studies for the occurence of specific microbes at stages
  • Surveillance at certain stages of production
  • Outbreak investigations
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9
Q

What are the microbiological standards (mandatory)

A
  • Used to determine the acceptability of a food with regard to a regulation or policy
  • Established by regulatory authorities
  • Foods not meeting the standard are subject to removal from the market
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10
Q

What are the microbiological specifications?

A
  • Used by buyers of a food purchasing a product that may be unacceptable safety and quality
  • Buyers throughout the food systems establish microbiological specifications for materials they produce
  • Specifications are advisory and the materials are sampled periodically
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11
Q

What are the microbiological guidelines?

A
  • Established by regulatory authorities, industrial trade associations or companies
  • Indicate the expected microbial content of food with practices
  • Food companies use guidlines as a bases to design and assess
  • Advisory in nature
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12
Q

Why is a representitive sample taken?

A

Sampling a food lot would destroy it therefore a representitive sample is a compromise

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13
Q

What is defined as a criterion?

A
  • What type of hazard (pathogen, genetic sequence), qualitative or quantitative
  • Food Category
  • Production or processing steps involved
  • Sampling plans
  • Interpretation
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14
Q

What are indicator organisms and pathogens?

A

Indicator organisms:
* General microbiota- synonyms: total aeorobic count, aerobic count- hygiene status of process
* Faecal coliforms (E.coli)- indication of faecal contamination

Pathogens- Salmonella, listeria monocytogenes, staphylococcus aureus

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15
Q

What should the sample plan define?
What are the different types?

A

‘The probability of detecting microorganisms in a lot’
Two class or three class sampling plan

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16
Q
  1. When are two class sampling plans used?
  2. What are its specficiations
A
  1. Used almost exclusively for pathogens, based on presence/absence
  2. Specifications:
    N= number of sample units from a lot to be examined
    M= maximum acceptable number of relevant bacteria
    C= maximum acceptable number of sample units that may exceed the value of M

Either satisfactory- counts below M or unsatisfactory

17
Q
  1. When is a three class sampling plan used?
  2. What are the specifications?
  3. How is it interperated?
A
  1. Often applied for indicator organisms
  2. Consist of the specifications- n, c, m and M
    c = number of sample units giving values between m and M
    M is used to seperate the acceptable from the unsatisfactory
    Interpretation
    Satisfactory if below m
    Acceptable if a maximum of c/n values are between m and M and the rest of the values are < m
    Unsatisfactory if one or more of the values observes are >M or more than c/n values between m and M
18
Q

What factors affect the development of microbiological criteria?

A
  • The availability of a risk assessment
  • Dose-response data
  • Consumer exposure data
  • Defined ALOP or FSO/PO
  • Data on microbial levels typically encountered in a food
19
Q

What decides what type of sample is taken?

A

May be dictated by regulations
Depends on material to be tested:
* Excision (carcass)
* Wet/dry swabbing (carcasses and surface equipment
* Whole carcass rinse (poultry)
* Meat sample (retail)
* Batch sample (food products, raw ingridients)

20
Q

Where are samples analysed?

A

In-house- poultry widely, must be accredited or supervised by accredited
Commercial- must be accredited and used recognised methods (ISO)

21
Q

What are the stages in sample processing?

A

Sampling
Transport
Removal of bacteria from sample
Examine for target organism
Confirm suspect colonies
Calculate and report results

22
Q

What are the two categories for sampling methods?

A

Destructive- excision with scalpel or borer
Non-destructive- wet/dry swabs

23
Q

What are the sample sites for TAC and enterobacteriaeae on cattle sheep and pigs?

A

Cattle- rump, flank, brisket and neck
Sheep- flank, brisket, thorax lateral, breast
Pig- ham, belly, back, Jowl

24
Q

What is the sampling area for salmonella?

A
25
Q

Why is destructive method of sampling better then non-destructive?

A

With non-destructive not all the bacteria can be removed off the swab

26
Q

Why do samples need to be diluted?

A

To make it possible to count samples

27
Q

Where is the most representive sample site in pigs and chickens?

A

Jowl

With pork and chicken the become wet in the processing system and water dribbles down

27
Q

Where is the most representive sample site in pigs and chickens?

A

Jowl

With pork and chicken the become wet in the processing system and water dribbles down

27
Q

Where is the most representive sample site in pigs and chickens?

A

Jowl

With pork and chicken the become wet in the processing system and water dribbles down

28
Q

What are problems associated with examination for pathogens?

A
  • Fastidious organisms- may be difficult to culture
  • Usually in low numbers and non-uniformly distributed- large no of samples needed
  • Negative result does not mean absence
  • Takes up to one week to isolate
  • Expensive
29
Q

What are the stages for isolation?

A

Pre-enrichment
Enrichment
Presumptive identificatoin
Identification

30
Q

What must happen with a test result before it is reported?

A

Must be confirmed:
Gram staining, biochemical tests, latex agglutionation (E.coli, S.aureus), serology (salmonella)

31
Q

How should test results be interpreted?

A
  • Sender should indicate the purpose of testing
  • For pathogens, plates examined and confirmed by further testing
  • For indicators, colonies on spread and pour plates counted
  • Results compared with microniological criteria
  • Report sent from lab to produced/consumer
32
Q

What factors of test may affect result?

A

All stages in sample processing
Microorganism not detectabe or damaged
Human error

Year 4 Public Health (13 decks)

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