proficiency testing in water and food...

Proficiency testing in water and food microbiology Collaboration between the Centre d’expertise

en analyse environnementale du Québec (CEAEQ)

and Canadian Association for laboratory Accreditation (CAlA)

CALA, CEAEQBerrouard, Mariane (CEAEQ); Middlebrook, Ken (CALA); Levert, Luc (CEAEQ)

Water microbiology Food microbiology

3. REliAbility, StAbility And HomogEnEity oF Pt SAmPlES

Our products are tested for every analyte, in every batch of samples for every study to assure that the proficiency testing samples you receive are homogenous and stable for the duration of the study (at least 96 hours after shipping). Therefore, you can reliably compare your results against similar laboratories.

Homogeneity tests - Homogeneity tests are first conducted by the CEAEQ with 5 samples analysed for every analyte by the microbiology laboratory at the same time by the same analyst.

- For each production lot of samples, a regression analysis is made by CALA on participants’ reported results against bottles serial numbers. A slope significantly different from zero would indicate a possible homogeneity problem.

Stability testsThe strains used in our transport media have shown over the years to be stable for up to one month at room temperature thus reducing the risk of variability between samples during shipping. This also ensures you that wherever your lab is or in case of unexpected events during shipping, the samples remain reliable.- 96 hours after samples shipping, the CEAEQ reanalyzes three samples at the same time by the same analyst. The results are then compared to those obtained from the analysis at time of shipping.

- CALA also produces a plot of the reported results against the date of analysis to make sure that there is no display of a trend in the data.

Media specificity checkEvery year, a verification of the typical characteristics on the more commonly used media used by the laboratory is made to assure no confusion for the analyst.

Our products are tested for every analyte, in every batch of samples for every study to assure that the proficiency testing samples you receive are homogenous and stable for the duration of the study (at least 1 month after shipping). Therefore, you can reliably compare your results against similar laboratories.

Homogeneity tests

- Homogeneity tests are first conducted by the CEAEQ on a minimum of 4 samples analysed for SPC by an accredited lab.

- For each production lot of samples, a regression analysis is made by CALA on participants’ reported results against bottles serial numbers. A slope significantly different from zero would indicate a possible homogeneity problem.

Stability testsThe strains used in our freeze dried samples have shown to be stable at least for a month (see figure 2).

- At shipping and after one month, 2 samples are analysed and compared for every analytes by an accredited laboratory.

- CALA also produces a plot of the reported results against the date of analysis to make sure that there is no display of a trend in the data.

Media specificity checkEvery year, a verification of the typical characteristics on the more commonly used media used by the laboratory is made to assure no confusion for the analyst.

Stability of samples for C61B (Milk) - Sample 1 during the CALA food microbiology in January 2014

0

0,5

1

1,5

2

2,5

3

2013-12-12

2013-12-22

2014-01-01

2014-01-11

2014-01-21

2014-01-31

2014-02-10

2014-02-20

2014-03-02

2014-03-12

2014-03-22

2014-04-01

date

SPC

coun

t val

ue (l

og)

spiking 1 month 2 months 3 months

Stability of samples for C61B (Milk) - Sample 2 during the CALA food microbiology in January 2014

0

0,5

1

1,5

2

2,5

2013-12-12

2013-12-22

2014-01-01

2014-01-11

2014-01-21

2014-01-31

2014-02-10

2014-02-20

2014-03-02

2014-03-12

2014-03-22

2014-04-01

date

SPC

coun

t val

ue (l

og)

spiking 1 month 2 months 3 months

The CEAEQ is an administrative entity of the «Ministère du Développement durable,

de l’Environnement et de la Lutte contre les changements climatiques du Québec».

The mission of the CEAEQ is: ensuring the availability, the quality and the continuity of

the expertise and the analytical information for the protection of the environment and

for the preservation of the resources. The main areas of activities of the CEAEQ are

environmental analysis in various fields such as biology, chemistry, ecotoxicology and

microbiology, quality system management and proficiency testing samples production.

The CEAEQ is accredited ISO/IEC 17025 since 1999 and ISO/IEC 17043 since 2005 by

the Standards Council of Canada. The Centre upholds high standards for management

system and administrative procedures, competent and qualified staff, reliable

installations and material and effective methods of quality control.

The Proficiency testing and reference material division of the CEAEQ applies the

guidelines of ILAC-G12-2000 and the international standard ISO/IEC 17043 for the

production of reference materials.

After having built a solid experience for producing reference materials for

accredited laboratories in Québec since 1984, the CEAEQ now produces Proficiency

Testing (PT) samples in water microbiology and, more recently, in food microbiology

for CALA proficiency testing.


4. REPoRting oF tHE RESultS And CommuniCAtion

The procedures are the same for water and food microbiology.

At all times, you can contact CALA or the CEAEQ and have quickly an answer to your questions.

Before the proficiency testingSix weeks before the study, CALA will notify the participating laboratories by email of the pending shipment.

One week before the proficiency test, the CEAEQ sends the samples tracking number with the exact shipping date. This allows the participating laboratories to follow their samples until they are received.

Instructions are available on Internet via the CALA website (www.CALA.ca) to allow the participant to print them and read them before the study.

Duration of the proficiency testingThe study duration is typically of 4-5 weeks during which time you can report your results using an easy to use Web-Data-Entry System.

In case of problems, replacement samples can be requested from CALA and quickly sent to allow the laboratory to participate to the proficiency test.

After the proficiency testingCALA provides a preliminary report within one week of the study closure. Final report is available within 3 weeks after the study is closed.

5. StAtiStiCS And intERPREtAtion oF RESultS

The assigned values are determined using the robust procedures detailed in ISO 13528.

The participants’ performance is evaluated using z-scores.

Performance is evaluated using z-scores, with |z| > 2.0 being questionable and |z| > 3.0 being unacceptable.

The assigned values are determined using the robust procedures detailed in ISO 13528 for log transformed data.

The participants’ performance is evaluated using z-scores.

Performance is evaluated using z-scores, with |z| > 2.0 being questionable and |z| > 3.0 being unacceptable.

6. StAtiStiCS About ouR PRogRAmS

In CEAEQ’s history of providing samples for the CALA PT program, no microbiology sample has had to be rejected.

The percentage of unsatisfactory (unacceptable) results from a participant generally runs between 4 and 10% per study.

The previous studies allow us to expect similar statistics in food microbiology as in water microbiology.

For more information about the water and food microbiology PT, please visit the CALA website at www.cala.ca or the CEAEQ website at www.ceaeq.gouv.qc.ca.

Figure 2

Sample’s stability during 3 months for SPC in C61B samples (Milk) during the January 2014 food microbiology proficiency testing.

The values of SPC counts are plotted against the analysis date to assess the sample’s stability at roughly 3 months. The analyses are made by CEAEQ collaborators (Health Canada and MAPAQ) that are accredited laboratories for food analysis. The samples are considered to be stable when results are within one log. The analyses are done with all tests groups and, by now, show similar results.

Table 1. Proficiency testing samples offered in food microbiology


1. HiStoRy oF tHE CollAboRAtion CAlA-CEAEQ in miCRobiology

The CEAEQ is the provider for proficiency testing samples for CALA in water microbiology since 2003 (C05A) and 2006 (C05B).

Over 20 studies in water microbiology were successfully conducted since the beginning of this collaboration.

In 2012, after the cancellation of the CFIA food microbiology PT sample production, the CEAEQ developed the expertise in food microbiology PT samples preparation in collaboration with CALA. Our methods of PT samples production are inspired from the CFIA protocols.

Since then, we provide “made in Canada”, easy to use and as close as possible to real samples for CALA proficiency testing program.

Five studies in food microbiology have been successfully conducted since the beginning of this collaboration.

2. PRoduCtS oFFEREd

Quantitative analysis for spread plate count (SPC), Total and Fecal (E. coli) coliforms (C05A).

Qualitative (Presence/Absence) of Total and Fecal (E. coli) coliforms (C05B).

Description of the PT samples:1- Preparation

- The samples consist of a 5ml concentrated microbial suspension in a liquid transport media.

- The transport media is sterile demineralised water with stabilizing chemicals added. It provides a good stability for microorganisms in various shipping conditions.

- The samples are spiked with environmental strains.- All the samples sent to the labs for the same Proficiency testing come from

the same batch.- All samples are aliquoted following their serial number (see figure 1). - Samples are easy to identify with color coded labels (see figure 1).

2- Requirements before the analysis- The samples are ready to use for SPC. - A dilution is required for the other parameters. Dilution procedure is detailed

in the instructions sheet provided by CALA.

3- Number of samples per year- 4 samples per study, 2 study per year for C05A and C05B.- The samples are usually sent in March and October each year.

Quantitative analysis in meat, milk, eggs and cheese for SPC, coliforms, E. coli and S. aureus (C60 to C63B).

Qualitative analysis in meat, milk, eggs, cheese and feed for Salmonella, Listeria, E. coli O157:H7 (C60 to C64A).

Description of the PT samples:1- Preparation

- The samples consist of a 5g freeze dried food matrix spiked with a microbial suspension. The samples are then freeze dried again and sealed under low oxygen atmosphere.

- The microbial suspension is made in a freeze drying liquid that helps to provide a good stability for the microorganisms until the analysis.

- The samples are spiked with environmental strains.- All the samples sent to the labs come from the same batch of freeze dried

matrix and the same microbial suspension.- All samples are aliquoted following their serial number (see figure 1). - Samples are easy to identify with color coded labels (see figure 1).

2- Requirements before the analysis- Rehydration in peptone water is required before analysis. - Rehydration procedure is detailed in the instructions sheet provided by CALA.- The rehydrated samples are similar to those received by any laboratory.

3- Number of samples per year- Refer to table 1.

Food matrix Parameter Test group # Sample/round # Round/year Month

Meat (Beef, chicken,

pork, ham)

Qualitative

Detection of : Salmonella sp.

Listeria sp. E. coli O157:H7

C60A 4 (1 per meat) 1 October

Quantitative

Numeration of : SPC

Coliforms E. coli

S. aureus

C60B 4 (1 per meat) 2 March, October

Milk

Qualitative



C61A 2 1 June

Quantitative

Numeration of : SPC

Coliforms S. aureus

C61B 2 2 January, June

Eggs

Qualitative



C62A 2 1 June

QuantitativeNumeration of :

SPC Coliforms

C62B 2 2 January, June

Cheese

Qualitative



C63A 2 1 October

Quantitative

Numeration of : E.coli

Coliforms S. aureus

C63B 2 2 March, October

Feed Qualitative Detection of : Salmonella sp. C64A 2 1 June

Identification of the study

Visual color identification of the sample and sample number

Test group

Serial number

Figure 1Water and food microbiology sets

All the samples are labelled with the identification of the study, the visual identification of the sample number (each sample has a line of a different color), the sample number, the CALA test group and the serial number. All the labels are applied and verified on the vial before the sampling for water microbiology and spiking for food microbiology.

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