4. AOACRIMicroMethods-2018Awards

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456 B ird et al .: J ournal of AOAC I nternational V ol . 100, N o . 2, 2017 were shipped on a Thursday via overnight delivery according to the Category B Dangerous Goods shipment regulations set forth by the International Air Transportations Association. The two matrixes were shipped consecutively, with collaborating laboratories performing analysis on one matrix at a time. Upon receipt, samples were held by the collaborating laboratory at refrigeration temperature (2–8°C) until the following Monday, when analysis was initiated after a total equilibration time of 96 h. All samples were packed with cold packs to target a temperature of <7°C during shipment.

the difference in collaborating laboratory POD (dLPOD) in the candidate presumptive and confirmatory results (dLPOD CP ), presumptive candidate results that confirmed positive (including those with presumptive negative results; POD C ), the reference method (POD R ), and the difference between the confirmed candidate and reference methods (dLPOD C ). A dLPOD C confidence interval not containing the value 0 would indicate a statistically significant difference between the 3M MDA 2 – Listeria monocytogenes and the reference method at the 5% probability level. In addition to POD, the repeatability SD (s r ), the among-laboratory repeatability SD (s L ), the reproducibility SD (s R ), and the homogeneity test of LPODs (P T ) value were calculated. The s r provides the variability of data within one laboratory, the s L provides the difference in SD among laboratories, and the s R provides the variability in data among different laboratories. The P T value indicates whether adequate sample homogeneity has occurred between laboratories. AOAC Official Method 2016.08 Listeria monocytogenes in a Variety of Foods and Select Environmental Surfaces 3M ™ Molecular Detection Assay (MDA) 2 – Listeria monocytogenes Method First Action 2016 {Applicable to the detection of Listeria monocytogenes in hot dogs (25 and 125 g), salmon (25 g), deli turkey (25 and 125 g), cottage cheese (25 g), chocolate milk (25 mL), vanilla ice cream (25 g), queso fresco (25 g), bagged raw spinach (25 g), romaine lettuce (25 g), melon (whole), raw chicken leg pieces (25 g), and raw chicken breast fillet (25 g), as well as on sealed concrete [3M Hydrated Sponge with Dey-Engley (D/E) Neutralizing Broth; 225 and 100 mL], stainless steel (3M Hydrated Sponge with D/E Neutralizing Broth; 225 mL), and plastic (high-density polyethylene; 3M EnviroSwab with Letheen Broth; 10 mL) environmental samples.} See Tables 2016.08A and 2016.08B for a summary of results of the interlaboratory study. See Tables 2016.08C and 2016.08D for detailed results of the interlaboratory study. The 3M Molecular Detection Assay (MDA) 2 – Listeria monocytogenes method is used with the 3M Molecular Detection System (MDS) for the rapid and specific detection of L. monocytogenes in enriched food and on food process environmental samples. The 3M MDA 2 – Listeria monocytogenes uses loop-mediated isothermal amplification of unique DNA target sequences, with high specificity and sensitivity, combined with bioluminescence to detect the amplification. Presumptive positive results are reported in real- time, whereas negative results are displayed after the assay is completed. Samples are pre-enriched in DF Broth with FAC broth. A. Principle

In addition to each of the test portions and a separate APC sample, collaborators received a test portion for each matrix labeled “temperature control.” Participants were instructed to obtain the temperature of this portion upon receipt of the package, document the results on the Sample Receipt Confirmation form provided, and fax or e-mail it back to the study director. The shipment and hold times of the inoculated test material had been verified as a QC measure before study initiation. Collaborators were instructed to follow the appropriate preparation and analysis as outlined in the study protocol for each matrix, for both the 3M MDA 2 – Listeria monocytogenes method and the reference method. For both matrixes, each collaborator received 72 test portions (12 high, 12 low, and 12 uninoculated controls for each method to be performed). For the analysis of the deli turkey test portions by the 3M MDA 2 – Listeriamonocytogenes method, a 125 g portionwas enriched with 1125 mL Demi-Fraser (DF) Broth with ferric ammonium citrate (FAC) broth, homogenized for 2 min, and incubated for 24–30 h at 37 ± 1°C. For the raw chicken breast fillet test portions analyzed by the 3M MDA 2 – Listeria monocytogenes method, a 25 g portion was enriched with 475 mL DF Broth, homogenized for 2 min, and incubated for 28–32 h at 37 ± 1°C. After enrichment, samples were assayed by the 3M MDA 2 – Listeria monocytogenes method and, regardless of presumptive result, confirmed using the USDA/FSIS MLG reference method. Both matrixes evaluated by the 3M MDA 2 – Listeria monocytogenes method were compared to samples analyzed using the USDA/FSIS MLG reference method in an unpaired study design. All positive test portions were biochemically confirmed by the API L. monocytogenes biochemical test or by the VITEK ® 2 Gram Positive Biochemical Identification Method, AOAC Official Method 2012.02 (8). Each collaborating laboratory recorded results for the reference method and the 3M MDA 2 – Listeria monocytogenes method on the data sheets provided. At the end of each week of testing, the data sheets were submitted to the study director for statistical analysis. Data for each matrix were analyzed using the probability of detection (POD) statistical model (9). POD statistical analysis was conducted using the AOAC Binary Data Interlaboratory Study Workbook , Version 2.3 (10). The PODwas calculated as the number of positive outcomes divided by the total number of trials. The POD was calculated for the candidate presumptive results (POD CP ), the candidate confirmatory results (excluding those with presumptive negative results; POD CC ), Test Portion Analysis Statistical Analysis

B. Apparatus and Reagents

Items b – g are available as the 3M MDA 2 – Listeria monocytogenes kit from 3M Food Safety (St. Paul, MN).

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