P3-51 Performance of the Atlas Listeria monocytogenes Detection Assay (LmG2) after a Single Enrichment

Wednesday, July 31, 2013
Exhibit Hall (Charlotte Convention Center)
Vanessa Bres, Roka Bioscience, San Diego, CA
Polina Zaslavsky, Roka Bioscience, San Diego, CA
Maesa Hanhan, Roka Bioscience, San Diego, CA
Paul Campbell, Roka Bioscience, San Diego, CA
Nathan Noll, Roka Bioscience, San Diego, CA
Ernie Hsu, Roka Bioscience, San Diego, CA
Hua Yang, Roka Bioscience, San Diego, CA
Joe Garcia, Roka Bioscience, San Diego, CA
Michael Reshatoff, Roka Bioscience, San Diego, CA
Michael Becker, Roka Bioscience, San Diego, CA
Introduction: Listeria monocytogenes (Lm) is a foodborne pathogen resulting in approximately 1,600 infections annually in the US. Listeriosis primarily affects the immunosuppressed, elderly, children, and pregnant women, causing severe health problems such as encephalitis, meningitis, septicemia, and miscarriage. Lmcontrol continues to be a food safety challenge given the organism’s ability to survive and grow under low pH, low temperature, and high salt.

Purpose:  To develop a molecular method for detecting Lmin 25g and 125g food portions and environmental samples with testing being performed after a single enrichment. 

Methods: Fractionally inoculated food samples and non-inoculated environmental samples are analyzed using the LmG2 assay, a messenger RNA (mRNA) based detection method with target specific to Lm. 25g food (ice cream, lettuce, chicken salad, hot dog, cured ham, frozen cream pie, frozen pizza, brie) and environmental samples are enriched at 35oC in PALCAM base with 0.02 g/L of Nalidixic acid for 24h, and a 26h enrichment is used for 125g food (cooked chicken and deli turkey) samples. Enriched samples are transferred to a proprietary lysis buffer, automatically purified via Target Capture, amplified by Transcription Mediated Amplification, and detected by Hybridization Protection Assay. Culture confirmation is performed by transferring 100 µl of enrichment to 10 ml of Fraser for 24h at 35oC and streaking onto MOX plates.

Results: The LmG2 assay provides positive results for 100% of Lm strains, and negative results for tested non-target microorganisms commonly found in food and grown to a titer ≥ 1E + 08 CFU/ml. The assay is equivalent to culture for all tested matrices. Similar equivalency is observed on environmental samples where positive samples are Lm confirmed.

Significance: The LmG2 assay specifically detects Lm in a variety of inoculated food matrices (25g and 125g) and non-inoculated environmental samples after 24h-26h enrichment on the Atlas system with equal sensitivity to culture.