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3M Petrifilm SALX Collaborative Study
July 2013
OMA-2013-July-XXX
DRAFT DOCUMENT
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5.11.7
Colonies may be subcultured for further identification. When subculturing, wear
1
appropriate protective apparel and follow standard good laboratory safety
2
practices (GLP).
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5.11.8
With a gloved hand, lift the top film and aseptically remove the colony either
4
from the gel or the 3M Petrifilm SALX Confirmation Disk. If a 3M Petrifilm SALX
5
Confirmation Disk is covering the gel, aseptically peel the disk away and then
6
aseptically remove the colony from the gel.
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5.11.9
Streak the colony onto/into media per appropriate reference method.
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5.11.10
NOTE:
If the colonies cannot be subcultured within 1 hour of plate removal from
9
the incubator, then store the 3M Petrifilm SALX Plates for later analysis by
10
placing in a sealed plastic bag at -20 to -10°C for no longer than 72 hours in the
11
dark. Allow 3M Petrifilm SALX Plates to warm to room temperature (20-25°C /
12
<60% RH) before continuing subculturing for identification.
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5.11.11 After the test is complete, dispose of the 3M Petrifilm SALX Plates and 3M
14
Petrifilm SALX Confirmation Disks in accordance with current industry standards
15
and/or local regulations.
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6.0
Reporting Raw Data
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6.1
Report data using the data report form in Appendix 8.2.
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6.2
Upon completion of each food type, the laboratory will fax or email the completed data
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form to the Study Director.
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6.3
Copies of all related test results (data sheets and confirmation results) should be
25
retained by the collaborating labs for a minimum of one year.
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7.0
Analyzing Raw Data
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The resulting data will be analyzed by two different calculations: probability of detection (POD)
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and relative limit of detection (RLOD).
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7.1
Probability of Detection (POD) -
POD is the proportion of positive analytical outcomes
33
for a qualitative method for a given matrix at a given analyte level or concentration.
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POD is concentration dependent. Please see the revised microbiology guidelines
1for
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complete analysis information on POD calculations.
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7.1.1
Calculate:
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7.1.1.1
Estimate of repeatability - standard deviation (s
r
)
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7.1.1.2
Determine POD values for each matrix and concentration -
the number
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of positive outcomes divided by the total number of trials.
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7.1.1.3
Estimate of reproducibility – standard deviation of the laboratory POD
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values (s
POD
) and confidence intervals.
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1
AOAC INTERNATIONAL Methods Committee Guidelines for Validation of Microbiological Methods for Food and
Environmental Surfaces (pre-publication document, 2012) Sharon Brunelle, Robert LaBudde, Maria Nelson, and
Paul Wehling
OMAMAN-08/Collaborative Study Protocol
March 2014
Expert Review Panel Use Only
AOAC Research Institute
Expert Review Panel Use Only