4. AOACRIMicroMethods-2018Awards

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four of these occurred in a singleANSR assay run of 15 samples. All but one of the false-positive results showed atypical, weak fluorescence curves, suggestive of cross-contamination during performance of the ANSR assay. Laboratory 13 reported five false-positive results. Again, all but one of these results showed atypical, weak fluorescence curves. Additionally, raw data received from this laboratory indicated that one assay run was repeated in total due to extreme aberrant results (i.e., invalid assays), suggesting that the technician was experiencing difficulty in performing the assay correctly. Including data from all 18 laboratories (with the exclusion of the six suspected contaminated samples from laboratory 16), accuracy on inclusive and exclusive strains was 99.9 and 96.5%, respectively. Considering only data from the 15 laboratories without clusters of aberrant results, accuracy on exclusive strains was 98.8%.

Table 4. Results by agar medium Medium a Correct

Misidentified Total

BGS

Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive Inclusive Exclusive

108

0 5 0 4 0 3 1 4 0 3 0 3 0 2 1

108 103 108 103 108 108 104 108 104 108 104 108 96

98

BS

108

99

DMLIA

108

93

HE

107 100 108 101 108 101 108

TSA

XLD

Recommendations

XLT-4

69

71

The ANSR Salmonella test was adopted as Official First Action status for use as a rapid, accurate adjunct or alternative to biochemical testing for identification of presumptive Salmonella spp. isolates.

Total

755 661

756 685

24

a  BGS = brilliant green sulfa agar; BS = bismuth sulfite agar; DMLIA = double-modified lysine iron agar; HE = Hektoen enteric agar; TSA = tryptic soy agar; XLD = xylose lysine deoxycholate agar; XLT-4 = xylose lysine tergitol agar.

Acknowledgments

We thank the following collaborators for their participation in this study: Dorn Clark and Hondo Dammann, Marshfield Food Safety (Marshfield, WI) Jessica Dyszel and Matthew Vross, Richter International (Columbus, OH) Nicole Cuthbert and Brian Kupski, Silliker (Crete, IL) Joe Benzinger, Megan Boyle, and Jonathan Flannery, Q Laboratories (Cincinnati, OH) Eric S. Adams, John B. Barrett, Mark E. Berrang, Douglas E. Cosby, Nelson A. Cox, Jonathan G. Frye, Lari M. Hiott, Charlene R. Jackson, Steven W. Knapp, and Luanne L. Rigsby, U.S. Department of Agriculture, Agricultural Research Service (Athens, GA) Robert Fuller and Jarrod Van Brunt, Tyson Foods (Springdale, AR) Hamoud Alnughaymishi and Andrew Scollon, Michigan State University, Department of Food Science and Human Nutrition (East Lansing, MI) Melanie Corebello and Erika Sai, Unilever U.S. (Englewood Cliffs, NJ) Lisa Kuepfer and Jill Stepnitz, Covance (Battle Creek, MI) Michael Hudgens andWalter Jones, NPAnalytical Laboratories (St. Louis, MO) DouglasWaltman and SelenaYork, Georgia Poultry Laboratory (Oakwood, GA) Jake Cannon, Benjamin Howard, and Neil Rogman, Certified Laboratories of the Midwest (Bolingbrook, IL) Chad Pidgeon and Amy Quenneville, Ben & Jerry’s (Burlington, VT) Vikas Gill and Hua Wang, United States Food and Drug Administration, Center for Food Safety and Applied Nutrition (College Park, MD) Cori Flores and Priyanwada Kulkarni, Henningsen Foods (Omaha, NE)

vulgaris produced colonies on XLT-4 agar. The remaining cases of no growth appeared to be random with respect to strain and medium. A total of 691 analyses were performed on exclusive strains. Collaborator 16 reported positive results on six of seven plates streaked with the E. cloacae culture. The remaining agar, TSA, was reported to have no growth. Collaborator 16 reported that the six plates all contained growth with colonies of a Salmonella -like appearance. It is concluded that this culture became contaminated at some point during preparation or analysis and therefore these data were eliminated from the statistical analysis. Of 685 remaining analyses, 661 produced negative results for accuracy with exclusive strains of 96.5%. Asummary of results by agar medium is shown in Table 4. The percentage of correct results was very similar for all seven media, ranging from 97.6 to 98.9%. In this multilaboratory evaluation of the ANSR Salmonella test for identification of presumptive Salmonella spp. isolates from agar media, the method exhibited exceptional accuracy with inclusive strains and a high degree of exclusivity with non- salmonellae. Of the 18 laboratories participating in the study, 15 reported results with overall accuracy of 99 to 100%. There was only a single false-negative result out of 756  Salmonella spp. colonies tested. Excluding data generated from a suspected contaminated slant culture, there were 24 false-positive results on non- Salmonella spp. colonies out of 685 colonies tested. All but seven of these aberrant results occurred in three laboratories. Laboratory 16 reported six false-positive results in addition to those linked to the contaminated slant culture. No further information is available for these samples, except that all six ANSR fluorescence curves were very strong, typical of true positive results. Laboratory 2 reported six false-positive results; Discussion

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