AOAC ERP MICRO AUGUST 2018

OMAMAN-44 A: Collaborative Study Manuscript Expert Review Panel Use Only August 2018

observed between the candidate method and the reference methods. The next requirement of the 383

harmonious MicroVal/AOAC validation is multi-laboratory collaborative study to demonstrate the 384

alternative method can be performed by laboratories routinely doing Enterobacteriaceae analyses and 385

to determine repeatability and reproducibility parameters to be assigned to the method. 386

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Collaborative Study Design

One matrix, powdered infant formula (milk based with iron and DHA) containing probiotics

( Lactobacillus reuteri ), was evaluated in this study. The matrix was obtained from a local retailer and 392

screened for the presence of naturally occurring Enterobacteriaceae by the ISO 21528-1 reference 393

method. No natural contamination was observed so four separate levels of contamination were 394

targeted for the evaluation: uninoculated, 0 colony forming unit (CFU)/g; low, 10–100 CFU/g; medium, 395

100–1,000 CFU/g; high 1,000–10,000 CFU/g. To obtain the required contamination levels, bulk lots of 396

the matrix were artificially contaminated with a lyophilized culture of Cronobacter sakazakii Q 397

Laboratories (QL) isolate 17031.4 (origin – powdered infant formula) at each target contamination level. 398

Two replicate samples from each of the four contamination levels were analyzed by both the candidate 399

and reference methods in a paired study design by each collaborating laboratory. 400

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A detailed collaborative study packet outlining all necessary information related to the study

including media preparation, test portion preparation and documentation of results was sent to each 402 ERP Use Only collaborating laboratory prior to the initiation of the study. A conference call was conducted prior to the 403 initiation of the study to discuss the collaborative study packet and answer any questions from the 404 participating laboratories. 405

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Preparation of the Inocula and Test Portions for the Collaborative Study

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