Verification of a Commercial Real-Time PCR Salmonella Detection Method on Individually Quick-Frozen Vegetable Matrices
Erica Miller 1, Christopher Crowe 2, and J. David Legan 3
Eurofins Microbiology Laboratories, Inc., 1 Louisville, KY, 2 Salinas, CA, 3 Madison, WI
ABSTRACT
Introduction
With increasing concerns and rising numbers of product recalls associated with pathogens in produce, most major PCR testing platforms are validated for detection of Salmonella in fresh produce. However, validations for other produce matrices are sparse, particularly for frozen matrices which can severely reduce initial temperatures of enrichment broths
Purpose
To verify the ability to detect Salmonella in frozen vegetable matrices utilizing real-time PCR.
Methods
Twenty-three different frozen vegetable matrices were tested, including cauliflower, carrots, various vegetable medleys, and chopped spinach: each with seven replicates (375g) inoculated with Salmonella ser Typhimurium at ca. 7.5 cfu/sample. All samples were enriched with 3,375 mL of BACGro™ Buffered Peptone Water (BPW) and incubated at 37°C for 21 ± 3 hours. Following incubation, samples were tested for Salmonella spp. using BACGene™ real-time PCR kits according to the manufacturer’s instruction. All proprietary media and tests kits were supplied by Gold Standard Diagnostics™.
Results
All seven replicates returned a presumptive positive result for Salmonella spp. for each of the 23 matrices, giving a total of 161 presumptive positive PCR results. The FDA microbiological method validation guidelines require 7/7 (or 19/20) presumptive results to consider a method extended to a new matrix, with no statistical analysis necessary. This standard was met for all 23 matrices in this study.
Significance
These data demonstrate that this method can reliably detect Salmonella spp. in a wide range of frozen vegetable matrices.
View the poster
Questions on how this information is applicable to your food process?
