Wednesday, August 3, 2016
America's Center - St. Louis
Erin Crowley, Q Laboratories, Inc., Cincinnati, OH
Benjamin Bastin, Q Laboratories, Inc., Cincinnati, OH
Jonathan Flannery, Q Laboratories, Inc., Cincinnati, OH
Patrick Bird, Q Laboratories, Inc., Cincinnati, OH
M. Joseph Benzinger, Jr., Q Laboratories, Inc., Cincinnati, OH
James Agin, Q Laboratories, Inc., Cincinnati, OH
David Goins, Q Laboratories, Inc., Cincinnati, OH
Introduction: Listeria’s ability to survive in extreme climates, such as low temperature and high pH, can cause severe problems for food manufacturers as the organism can survive cleaning conditions and contaminate food commodities. While less frequent than other food borne pathogens, outbreaks from
Listeria monocytogenes have been linked to a variety of food types, such as raw milk cheeses, pasteurized dairy products, smoked seafood, deli meats, hot dogs, and cantaloupe. The presence of other
Listeria species
, such as
L. innocua, L. welshimeri or L. ivanovii is often used as an indicator for the possible contamination of
L. monocytogenes. The Bio-Rad iQ-Check
® Listeria spp. Kit is based on gene amplification and detection by real-time PCR. Ready-to-use PCR reagents contain oligonucleotides (primers and probes) specific for
Listeria species, as well as DNA polymerase and nucleotides. The Free DNA Removal Kit inhibits the amplification of target DNA from non-viable cells.
Purpose: The purpose of this independent evaluation was to compare the new method, including the Free DNA removal step, to the USDA-FSIS 8.09 method for deli ham (25g), stainless steel (1 x 1 swabs) and sealed concrete (4" x 4" sponges) environmental surfaces and the AOAC993.12 method for cheddar cheese (125 g)as part of the AOAC RI™ PTM validation process.
Methods: Using 30 unpaired samples for each matrix, 5 replicates were inoculated at a high inoculation level, 20 at a low inoculation level and evaluated along with 5 uninoculated control replicates. After sample enrichment in Bio-Rad Listeria Special Broth, test portions were evaluated by both the new and reference methods. Samples were confirmed following procedures outlined in the USDA/FSIS-MLG8.09 or AOAC993.12.
Results: Results for the assay were compared to the MLG and AOAC reference methods by POD analysis. No statistically significant differences were observed between the new method and the reference methods in the 2 foods and 2 environmental surfaces.
Significance: The data from the study, within the statistical uncertainty, support the product claims of the iQ-Check® Listeria spp. Kit and enhanced sensitivity in detection of Listeria species using the Free DNA removal protocol in the select food matrices and environmental surfaces analyzed.
