P3-167 Validation of Individual and Wet Pooled Environmental Sample Analyses in Buffered Peptone Water and Lactose Broth by the Atlas Salmonella Sen Detection Assay

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
William Chaney , Roka Bioscience , San Diego , CA
Benjamin Bastin , Q Laboratories, Inc. , Cincinnati , OH
Patrick Bird , Q Laboratories, Inc. , Cincinnati , OH
Joe Benzinger , Q Laboratories, Inc. , Cincinnati , OH
Ali DeShields , Q Labs , Cincinnatti , OH
Erin Dreyling , Roka Bioscience , Warren , NJ
Introduction: Wet compositing or “pooling” of analytical samples post-enrichment for rapid pathogen detection is a cost-effective and common practice, however, many methods have not been validated for this practice, which may increase false negative risk via dilution and loss of analytical sensitivity.

Purpose:  To validate the Atlas Salmonella SEN Detection Assay for the analyses of individual or 5 sample wet composited environmental sponge samples enriched in BPW or Lactose broth.

Methods: Sixty, 4”×4” stainless steel coupons were utilized for surface inoculation. Ten replicates were non-inoculated, 40 were inoculated at a low-level and 10 at a high level to approach POD=1. Samples were inoculated with Salmonella Derby (ATCC #6960) and 10X Citrobacter freundii(ATCC #6879) and allowed to dry overnight. Surfaces were sampled with sponge swabs pre-hydrated with D/E neutralizing broth. Half of the test samples were enriched with 190mL BPW for 20 hours at 42°C and half with 225mL Lactose broth for 24 hours at 35°C. Post enrichment, 1ml of each sample was combined with 4mL of non-inoculated sample enrichment to form a 5 sample wet composite. Both individual and pooled samples were assayed by the SEN method in duplicate using 12 and 400µL analytical volumes as well as by FDA BAM 5 cultural analysis.

Results: For individual and wet pooled samples in BPW, SEN detected 9 and 5 presumptive positives from the low and high level replicates, respectively, and for the 12µL and 400µL analytical volumes. For individual and wet pooled samples in Lactose broth, SEN detected 8 and 5 presumptive positives across the study parameters. All presumptive results correlated 100% with FDA BAM 5 reference culture results.

Significance: These data support the application of the SEN assay for the accurate analyses of individual or 5 sample wet composited environmental samples enriched in BPW or Lactose broth.