AOAC 2017 First Action Methods

Table 2017.05D. Summary of the results for the detection of E. coli O157:H7 in 73% lean raw ground beef (325 g) using the mericon E. coli O157 STEC O-Type assay with automated QIAsymphony extraction a Inoculation level Uninoculated Low High Candidate presumptive positive/total No. of samples analyzed 1/144 63/144 141/144 Candidate presumptive LPOD CP 0.01 (0.00, 0.04) 0.44 (0.35, 0.52) 0.98 (0.94, .99) s r 0.08 (0.07, 0.16) 0.51 (0.45, 0.52) 0.14 (0.13, 0.16) s L b 0.00 (0.00, 0.03) 0.00 (0.00, 0.16) 0.00 (0.00, 0.15) s R 0.08 (0.08, 0.10) 0.51 (0.46, 0.52) 0.14 (0.13, 0.16) P -value c 0.4368 0.8105 0.6042 Candidate confirmed positive/total No. of samples analyzed 0/144 65/144 144/144 Candidate confirmed LPOD CC 0.00 (0.00, 0.03) 0.45 (0.37, 0.54) 1.00 (0.97, 1.00) s r 0.00 (0.00, 0.16) 0.51 (0.45, 0.52) 0.00 (0.00, 0.16) s L 0.00 (0.00, 0.16) 0.00 (0.00, 0.15) 0.00 (0.00, 0.16) s R 0.00 (0.00, 0.22) 0.51 (0.46, 0.52) 0.00 (0.00, 0.22) P -value 1.0000 0.8479 1.0000 Candidate confirmed positive/total No. of samples analyzed 0/144 63/144 141/144 Candidate presumptive positive that confirmed LPOD C 0.00 (0.00, 0.03) 0.44 (0.35, 0.52) 0.98 (0.94, 0.99) s r 0.00 (0.00, 0.16) 0.51 (0.45, 0.52) 0.14 (0.13, 0.16) s L 0.00 (0.00, 0.16) 0.00 (0.00, 0.16) 0.00 (0.00, 0.15) s R 0.00 (0.00, 0.22) 0.51 (0.46, 0.52) 0.14 (0.13, 0.16) P -value 1.0000 0.8105 0.6042 Positive reference samples/total No. of samples analyzed 0/144 65/144 144/144 Reference LPOD 0.00 (0.00, 0.03) 0.45 (0.37, 0.54) 1.00 (0.97, 1.00) s r 0.00 (0.00, 0.16) 0.51 (0.45, 0.52) 0.00 (0.00, 0.16) s L 0.00 (0.00, 0.16) 0.00 (0.00, 0.15) 0.00 (0.00, 0.16) s R 0.00 (0.00, 0.22) 0.51 (0.46, 0.52) 0.00 (0.00, 0.22) P -value 1.0000 0.8479 1.0000 dLPOD: candidate versus reference d 0.00 (–0.03, 0.03) –0.01 (–0.13, 0.10) –0.02 (–0.06, 0.01) dLPOD: candidate presumptive versus candidate confirmed d 0.00 (–0.02, 0.04) –0.01 (–0.13, 0.10) –0.02 (–0.06, 0.01) a  Results include 95% confidence intervals. b  Among-laboratory SD. c P -values derived from the homogeneity test of laboratory PODs. d  A confidence interval for dLPOD that does not contain a zero value indicates a statistically significant difference between the two methods.

inventory scan of the “Waste” drawer, including the tip chute and liquid waste. Replace the tip disposal bag, if necessary. ( 2 ) Load an elution microtube rack into the “Eluate” drawer and perform an inventory scan of the “Eluate” drawer. ( 3 ) Load the QIAsymphony mericon Bacteria Kit and consumables into the “Reagents and Consumables” drawer. Select the “R+C” button in the touchscreen to open the screen that shows the consumables status (“Consumables/8-RodCovers/Tubes/Filter-

Tips/Reagent Cartridges”). Select the “Scan Bottle” button to scan the bar code of the TopElute bottle with the handheld bar code scanner. Select the “OK” button. ( 4 ) Performan inventory scan of the “Reagents andConsumables” drawer. ( 5 ) Transfer 500 μL enriched sample into a 2 mL screw-cap tube. Place the samples into the appropriate tube carrier and load them into the “Sample” drawer.

Table 2017.05I. Sample enrichment and incubation Matrix

Sample size, g Homogenization process Enrichment media and volume Incubation conditions

Fresh spinach

25

Stomach for 1.5 min ± 10 s Stomach for 2 min ± 10 s Stomach for 2 min ± 10 s

mTSB/225 mL mTSB/975 mL mTSB/975 mL

42 ± 1°C for 10 h 42 ± 1°C for 10 h 42 ± 1°C for 10 h

Raw ground beef (73% lean)

325 325

Raw beef trim

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