AOAC ERP MICRO AUGUST 2018

82 B ird et al .: J ournal of AOAC I nternational V ol . 100, N o . 1, 2017

FOOD BIOLOGICAL CONTAMINANTS

Evaluation of 3MMolecular Detection Assay (MDA) 2– Listeria  for the Detection of Listeria Species in Select Foods and Environmental Surfaces: Collaborative Study, First Action 2016.07 P atrick B ird , J onathan F lannery , E rin C rowley , J ames A gin , and D avid G oins Q Laboratories, Inc., 1400 Harrison Ave, Cincinnati, OH 45214 L isa M onteroso 3M Food Safety Department, 3M Center, Bldg 260-6B-01, St. Paul, MN 55144 Collaborators: C. Barnes; B. Bastin; D. Baumler; D. Bosco; A. Brandt; R. Brooks; E. Budge; A. Calle; D. Campos; C. Chavarria; C. Diaz Proano; Z. Geurin; C. Gies; F. Hernandez; D. Isfort; C. Lopez; L. Ma; E. Maranan; Z. Metz; J. Miller; A. Repeck; B. Schindler; M. Shekhawat; E. Sjogren; R. Smith; C. Timmons; G. Trevino; J. Walia; D. Wood; C. Zook

3M Molecular Detection Assay (MDA) 2– Listeria uses loop-mediated isothermal amplification and bioluminescence detection to rapidly detect Listeria species in a broad range of food types and environmental surfaces. Using an unpaired study design, MDA 2– Listeria was compared with the U.S. Department of Agriculture, Food Safety and Inspection Service’s Microbiology Laboratory Guidebook Chapter 8.09 “Isolation and identification of Listeria monocytogenes from red meat, poultry and egg products, and environmental samples” reference method for the detection of Listeria in deli turkey and raw chicken breast fillet. Technicians from 13 laboratories located within the continental United States and Canada participated in the collaborative study. Each matrix was evaluated at three levels of contamination: uninoculated control (0 CFU/test portion), low inoculum (0.2–2 CFU/test portion), and high inoculum (2–5 CFU/test portion). Statistical analysis was conducted according to the probability of detection (POD) statistical model. Results obtained for the low-inoculum-level test portions produced a difference between two laboratory POD values (dLPOD) with 95% confidence intervals of 0.04 (–0.08, 0.17) for deli turkey, indicating the difference between the methods was not statistically significant at the P = 0.05. For raw chicken breast fillet, a dLPOD value with 95% confidence interval of 0.16 (0.04, 0.28) indicated a statistically significant Received July 25, 2016. Accepted by AH August 23, 2016. This method was approved by the Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces as First Action. The Expert Review Panel for Microbiology Methods for Food and Environmental Surfaces invites method users to provide feedback on the First Action methods. Feedback from method users will help verify that the methods are fit-for-purpose and are critical for gaining global recognition and acceptance of the methods. Comments can be sent directly to the corresponding author or methodfeedback@aoac.org. Corresponding author’s e-mail: pbird@qlaboratories.com Supplemental information is available on the J. AOAC Int . Web site, http://aoac.publisher.ingentaconnect.com/content/aoac/jaoac DOI: 10.5740/jaoacint.16-0236

difference between the two methods, with an observed higher proportion of positive results by the candidate method than the reference method. L isteria, a hardy Gram-positive, rod-shaped bacterium, is often found in food-manufacturing facilities, leading to the contamination of food commodities (1). Due to the ubiquitous nature of Listeria , this organism is used as a hygiene indicator in all stages of the food-processing chain. Detection of Listeria in production and processing facilities may be an indicator of unsanitary conditions (2). The organism’s ability to survive in extreme conditions makes its presence in food a serious issue. In the past year, Listeria has been identified as the source of several high-profile outbreaks involving bagged leafy greens and ice cream (3). The 3M Molecular Detection Assay (MDA) 2– Listeria method (3M Food Safety, St. Paul, MN), using a combination of bioluminescence and isothermal amplification of nucleic acid sequences, allows for rapid and specific detection of Listeria species in a broad range of food types and environmental surfaces after 24–32 h of pre- enrichment. After enrichment, samples are evaluated using 3M MDA 2– Listeria on the 3M Molecular Detection System. Presumptive-positive results are reported in real time, whereas negative results are displayed after completion of the assay in approximately 75 min. Prior to the collaborative study, the 3M MDA 2– Listeria method was validated according to AOAC INTERNATIONAL guidelines (4) in a harmonized AOAC Performance Tested Methods SM (PTM) study. The objective of the PTM study was to demonstrate that the 3M MDA 2– Listeria method could detect Listeria in a broad range of food matrixes and environmental surfaces as claimed by the manufacturer. For the 3M MDA 2– Listeria PTM evaluation, 13 matrixes were evaluated: hot dogs (25 and 125 g); salmon (25 g); deli turkey (25 and 125 g); cottage cheese (25 g); vanilla ice cream (25 g); queso fresco (25 g); spinach (25 g); melon (whole); raw chicken leg pieces (25 g); raw chicken fillet (25 g); and concrete (sponge, 225 and 100 mL), stainless steel (sponge, 225 mL), and plastic (Enviro Swab, 10 mL) environmental samples. Additional PTM parameters (inclusivity, exclusivity, ruggedness, stability, and lot-to-lot variability) tested in the PTM studies satisfied the performance requirements for PTM approval.

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