Purpose: Consistent with last year, to compare the equivalence of sample preparation for Assurance GDS analysis performed manually using the PickPen device and in an automated manner utilizing the Assurance GDS PickPen PIPETMAX (PPMX) instrument equipped with a PickPen head in a variety of new and challenging foods by multiple Assurance GDS methods.
Methods: A total of 323 samples of various matrices were analyzed by multiple Assurance GDS methods. Inoculated samples were enriched according to kit directions for use. Paired samples were taken. One set was prepared manually while the other set was processed by the PPMX. Both sets of prepared samples were analyzed on the BioControl Rotor-Gene Q instrument. Positives were confirmed and matched for the two sample comparative preparation methods and Ct (amplification cycle threshold) values compared for all positive samples.
Results: A total of 375 samples were tested. 274 samples were confirmed positive with both the manually processed and those prepared using the PPMX automated system. 101 samples were negative by both methods. There were no discrepant results. The mean Ct values across all the positive curves were within 0.3 of each other. Four different Assurance GDS assays were evaluated. In total, five different foods and three surfaces were tested. They are known to be challenging due to factors such as heavy particulates, inhibitory materials, high microbial load.
Significance: This validation study demonstrates the equivalence of the Assurance GDS sample preparation method comparing manual processing with the new automated system, the Assurance GDS PickPen PIPETMAX for a growing number of difficult food matrices and surfaces.