4. AOACRIMicroMethods-2018Awards

142

820  B ird et al . : J ournal of AOAC I nternational V ol . 96, N o . 4, 2013

presented in Table 2013.01B and in appended Table E and Figure 2C and D.

Discussion

For this collaborative study, samples were analyzed at both 375 and 25 g test portions as required by the current AOAC guidelines, which require methods with more than one sample preparation or enrichment scheme to analyze one matrix per procedure. For the analysis of 375 g test portions, no significant difference was observed using the POD statistical model in the number of positive results obtained between the two methods being compared using both the traditional and alternative confirmation procedures for the VIDAS SPT method. For the analysis of 25 g test portions, a significant difference was observed using the POD statistical model between the two methods for both the low and high levels of inoculation using both the traditional and alternative confirmation procedures, with more positive results obtained using the VIDAS SPT method, indicating a high level of sensitivity in the detection of the target analyte by the candidate method. The results of the POD statistical analysis may indicate the high sensitivity of the VIDAS SPT assay. The VIDAS SPT showed a higher sensitivity than the reference method when test portions of the same size (25 g) were analyzed, and similar sensitivity to the reference method for test portions that were 15x larger (375 g VIDAS SPT test portions, compared to 25 g USDA/FSIS-MLG test portions). No negative feedback was reported to the Study Directors from the collaborating laboratories with regard to the performance of the VIDAS SPT assay or the IBISA and ASAP chromogenic agar. Overall, the VIDAS SPT method recovered Salmonella in 475 test samples out of 826 samples analyzed, compared to 411 positive results out of 826 samples for the USDA/FSIS-MLG method. Only one unconfirmed positive result and no false-negative results were obtained using the VIDAS SPT method. It is recommended that the VIDAS SPT method, with the optionalASAP and IBISAagar confirmation method, be adopted as Official First Action status for the detection of Salmonella in a variety of foods, including raw ground beef (25 and 375 g), processed American cheese (25 g), deli roast beef (25 g), liquid egg (25 g), peanut butter (25 g), vanilla ice cream (25 g), cooked shrimp (25 g), raw cod (25 g), bagged lettuce (25 and 375 g), dark chocolate (375 g), powdered eggs (25 g), instant nonfat dry milk (25 and 375 g), ground black pepper (25 g), dry dog food (375 g), raw ground turkey (375 g), almonds (375 g), chicken carcass rinsates, and stainless steel, plastic, and ceramic environmental surfaces. Recommendations We extend our sincere thanks to the following collaborators for their dedicated participation in this study: John Mills, bioMérieux Industry, Hazelwood, MO JudyNogle, U.S. Food andDrugAdministration, San Francisco District Office, Alameda, CA Willis Fedio and Ruben Zapata, New Mexico State University, Center for Animal Health, Food Safety and Biosecurity, Las Cruces, NM Acknowledgments

Alternative Confirmation with IBISA and ASAP

For the high level, 130 of 132 test portions were reported as positive by the VIDAS SPT method, with all portions confirming positive. For the low level, 57 of 131 test portions were reported as positive by the VIDAS SPT method, with 58 confirming positive. For the uninoculated controls, none of the 132 samples produced a presumptive positive result by the VIDAS SPT method, and all samples confirmed negative. For test portions analyzed by the USDA/FSIS-MLG method, 131 of 132 high and 54 of 132 low inoculum test portions confirmed positive. For the uninoculated controls, none of the 132 test portions confirmed positive. For the low-level inoculum, dLPOD C values of 0.03 (–0.18, +0.24) were obtained between the USDA/FSIS-MLG method and the VIDAS SPT method. The confidence intervals obtained for dLPOD C indicated no significant difference between the two methods. dLPOD CP values of –0.01 (–0.21, +0.23) were obtained between presumptive and confirmed VIDAS SPT results. The confidence intervals obtained for dLPOD CP indicated no significant difference between the presumptive and confirmed results using either confirmation process. For the high-level inoculum, dLPOD C values of –0.01 (–0.05, +0.03) were obtained between the USDA/FSIS-MLG method and the VIDAS SPT method. The confidence intervals obtained for dLPOD C indicated no significant difference between the two methods. dLPOD CP values of 0.00 (–0.04, +0.04) were obtained between presumptive and confirmed VIDAS SPT results. The confidence intervals obtained for dLPOD CP indicated no significant difference between the presumptive and confirmed results. Detailed results of the POD statistical analysis are presented in Table 2013.01B and in appended Table F and Figure 2E and F. Results obtained from the IBISA and ASAP chromogenic agars were comparable to the results obtained from the XLT4 and BGS agars specified by the USDA/FSIS-MLG method. For the samples analyzed by the reference method, there were 412 positive results obtained from ASAP agar plates, compared to 411 positive results obtained from XLT4 and BGS agar plates. For samples analyzed by the VIDAS SPT method and confirmed following traditional procedures using IBISA and ASAP there were 476 positive results obtained from ASAP agar plates, compared to 475 positive results obtained from IBISA, XLT4 and BGS agar plates. For samples analyzed by the VIDAS SPT method and confirmed following the alternative procedure using IBISA and ASAP, there were 479 positive results obtained from IBISA and ASAP agar plates, compared to 475 positive results obtained from XLT4 and BGS agar plates. Four uninoculated control samples produced positive results on the IBISA and ASAP chromogenic agar that were not detected on either the XLT4 or BGSA reference agars or during analysis with the VIDAS SPT assay. Because the Salmonella species was not detected on the two reference agar plates, the positive results produced by the chromogenic agar plates may be an artifact of cross-contamination or laboratory error. 03/10/2019 IBISA and ASAP Chromogenic Agar