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laboratory did continue analysis of the test portions. For each
sample, TNTC results were obtained on all dilutions prepared
for both the 3M Petrifilm RAC plate and the SMEDP reference
method agar plates. The coordinating laboratory was notified of
the shipment error and no additional data were submitted for the
matrix. Laboratory 6 indicated to the coordinating laboratory
that their sample test portions were stored at room temperature
(24 ± 2°C) upon receipt for 24 h prior to analysis. For each
sample, TNTC results were obtained on all dilutions prepared
for both the 3M Petrifilm RAC plate and the SMEDP reference
method agar plates. The coordinating laboratory was notified of
the error and no additional data were submitted for the matrix.
No statistically significant difference was observed between
the 3MPetrifilmRAC Plate and FDABAMor SMEDP reference
methods for all three matrixes evaluated when compared using
the difference of means, including 95% CI. Based on the data
presented, the reproducibility values obtained for the three
matrixes for all three contamination levels were generally
similar between the candidate and reference methods, indicating
that both the between-laboratory variations and within-
laboratory variations were consistent between the candidate and
reference method. These values indicate that for reproducibility,
no meaningful statistical differences were observed in the data
between the candidate and reference methods when test portions
were analyzed by different analysts at each laboratory or within
each sample set at a given laboratory.
Recommendations
It is recommended that the 3M Petrifilm RAC Plate be
adopted as Official First Action status for the enumeration of
aerobic bacteria from raw ground beef, raw ground pork, raw
ground turkey, chicken carcass rinsate, fresh swai, fresh tuna,
fresh tiger shrimp, raw easy-peel shrimp, cherry tomato wash,
frozen blueberries, Mediterranean apricots, creamy salad
dressing, fresh pasta, vanilla ice cream, instant NFDM, and
pasteurized skim milk.
Acknowledgments
We extend a sincere thank you to the following collaborators
for their dedicated participation in this study:
Leslie Thompson (Vanguard Sciences, North Sioux City, ND)
Heidi Wright (AEMTEK Inc., Freemont, CA)
Luci Hardrath (AGSOURCE Laboratories, Marshfield, WI)
Wendy McMahon, Brian Kupski, and Nicole Cuthbert
(Silliker Food Science Center, Crete, IL)
Joe Meyer and Jean Schoeni (Covance Laboratories,
Madison, WI)
Karilyn Gonzales and Chelsea Fagundes (Food
Microbiological, Cypress, CA)
Chris Lopez, Alex Brandt, and Bharath Brahmanda (Food
Safety Net Services, San Antonio, TX)
Joey Marchant-Tambone (FDA. CFSAN Gulf Coast Seafood
Laboratory, Dauphin Island, AL)
Adam Hankins (McCoy & McCoy Laboratories, Inc.,
Madisonville, KY)
Ashley Morris and Robert Brooks (Microbac Laboratories,
Inc., Maryville, TN)
Karen Beers (Safe Foods/MCA, Rogers, AR)
Jerri Lynn Pickett, Joseph Reynolds, and Kierra Payne-
McDaniel (Tyson-WBAAnalytical, Springdale, AR)
Dora Rodgers and Kate Angeles (Wisconsin Department
of Agriculture, Trade and Consumer Protection Bureau of
Laboratory Services, Madison, WI)
Brenda Brown (Murray Brown Laboratories LLC,
Madison, WI)
Kevin Miller (Marshfield Food Safety, LaCrosse, WI)
Allison Mastalerz (Q Laboratories, Inc., Cincinnati, OH)
We also extend special thanks to the following team members
at Q Laboratories, Inc. for their efforts during the collaborative
study: M. Joseph Benzinger, Jr., Kiel Fisher, Megan Boyle,
Ben Bastin, Alison DeShields, Emmanuel Onuoha, T. Shane
Wilson, Erica Lee, and Nicole Klass.
Figure 8. Youden plot for combined mean 3M Petrifilm RAC Plate and SMEDP results for instant NFDM.