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P1-26 FERN Multi-laboratory Evaluation of MicroSEQ® Salmonella spp. Detection Kit in Comparison with an FDA Rapid Screening qPCR Method

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Chorng-Ming Cheng, U.S. Food and Drug Administration, Irvine, CA
Tara Doran, U.S. Food and Drug Administration, Rockville, MD
Wen Lin, U.S. Food and Drug Administration-ORA-DFS, Rockville, MD
Kai-Shun Chen, U.S. Food and Drug Administration, Irvine, CA
Donna Williams-Hill, U.S. Food and Drug Administration, Irvine, CA
FERN Laboratory Cadre, FERN, rockville, MD
Ruiqing Pamboukian, U.S. Food and Drug Administration, Rockville, MD
Introduction:  Salmonella spp. are the most frequently reported cause of foodborne illness worldwide. To augment time-consuming conventional culture methods, the FDA developed a qPCR method for rapid screening purposes. This method has been shown to be reliable and accurate and has been validated by the FERN (Food Emergency Response Network) in a multi-laboratory validation study using both ABI 7500 FAST and SmartCycler II systems.  The method is used routinely by the FERN and in FDA mobile laboratory deployments. To expand the repertoire of available molecular diagnostic tests for Salmonella in foods, the FERN has conducted a similar multi-laboratory validation study to evaluate the performance of the MicroSEQ® Salmonella spp. Detection Kit (Life Technologies, Inc.).

Purpose:   To compare the sensitivity and specificity of the MicroSEQ® Salmonella spp. to those performance parameters previously validated for the FDA qPCR rapid screening method for Salmonella.

Methods:  Four food types (chili powder, soft cheese, fish and tomatoes) were inoculated at three levels (six replicates for each) – uninoculated, low (1-5 CFU/25g) and high (10-50 CFU/25g).  All samples were tested for Salmonella using the 24-hr qPCR method which utilizes modified Buffered Peptone Water (mBPW) as the sole enrichment medium.  Eighteen samples for each food type were independently analyzed by the participating laboratories using the MicroSEQ® Salmonella spp. Detection Kit in parallel with the qPCR method using both ABI 7500 FAST and SmartCycler II systems.

Results:  For all food types, the sensitivity is 1/288 for FDA qPCR and 2/288 for MicroSEQ®. The selectivity is 513/576 for FDA qPCR and 515/576 for MicroSEQ® indicating that there was no significant difference (P ≥ 0.05) statistically between the MicroSEQ® Salmonella spp. Detection Kit method and the corresponding reference methods.

Significance:  The consistent results among 12 laboratories support the utility of the MicroSEQ® Salmonella spp. Detection Kit as an alternative method for detecting Salmonella in food.

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