Start | Browse by Day | Author Index | Personal Scheduler

P1-112 Validation of BAX® System Real-time PCR Assay for Detection of Shigella in Foods

Monday, July 23, 2012
Exhibit Hall (Rhode Island Convention Center)
Linda Xuan Peng, DuPont Qualicon, Wilmington, DE
Dan Delduco, DuPont Qualicon, Wilmington, DE
Julie Kraynak, DuPont Qualicon, Wilmington, DE
Gongbo Wang, DuPont Qualicon, Shanghai, China
Jun Luan, Jiangsu CIQ, Nanjing, China
Changqing Zhu, Inspection and Quarantine Bureau, Nanjing, China
Yiqian Wang, Zhangjiagang CIQ, Zhangjiagang, China
Yang Zhou, Anhui Agricultural University, Hefei, China
Rui Zhang, Jiangsu CIQ, Nanjing, China
Yuan Jiang, Jiangsu CIQ, Nanjing, China
Introduction: A Scorpion™ probe-based real-time PCR assay and accompanying culture confirmation method were developed to detect Shigella species in foods. The specificity of the assay was demonstrated with a diverse range of Shigella species, related organisms, and unrelated genera. The assay was sensitive enough to detect less than 100 CFU/ml of the target pathogen in both pure broth culture and food samples.

Purpose: The objective of this study was to evaluate the BAX® System assay for detecting Shigella in foods using an enrichment in standard Shigella enrichment broth. Sample enrichment in BAX® System MP media was also evaluated to allow for testing of Shigella, Salmonella and E. coli O157:H7 from a single enrichment.

Methods: Various foods including raw and ready-to-eat meats, jelly and produce were spiked with Shigella species at levels likely to obtain fractional positives. Samples were enriched in either standard Shigella broth (as described in FDA-BAM Chapter 6, ISO21567 and new China National Standard GB4789.5) or BAX® System MP media for 8 – 20 hours, then prepared and processed according to the standard BAX®System protocol. All samples were confirmed with the appropriate reference culture method.

Results: In foods with low background microflora, such as ready-to-eat meat and jelly, the BAX® System method detected Shigella in 8-20 hours with 100% sensitivity and specificity regardless of enrichment method. Chi-square analysis indicates that the test method and the reference methods returned statistically equivalent results. For the remaining sample types, only slight differences were found between samples enriched with standard media and BAX® System MP media. Chi-square analysis indicates that these differences are not statistically significant, demonstrating that BAX® System MP media performs comparably to Shigella broth for the enrichment of Shigella in these food types.

Significance: Because this study demonstrates that the BAX® System method is comparable to the reference method and that BAX® System MP media can be used to enrich samples for Shigella testing, these results suggest that it is possible to enrich certain samples for Shigella, Salmonella and E. coli O157:H7 testing from a single 8 – 20 hour enrichment in BAX® System MP media, saving time, effort and expense for customers. However, it remains a challenge to isolate Shigella spp. from certain foods which has high background microflora such as raw pork using conventional culture media.

Back to: Technical and Poster Abstracts
<< Previous Abstract | Next Abstract >>