Method Modification for the Atlas Listeria Environmental LE Detection Assay Using FoodChek Actero Listeria Enrichment Media and Half-Fraser Media for the Detection of Listeria spp. from Environmental Surfaces.

Two candidate method modifications for the Atlas Listeria Environmental LE Detection Assay were compared with the U.S. Department of Agriculture (USDA)-Food Safety and Inspection Service Microbiology Laboratory Guidebook 8.09 (MLG 8.09) method for detection of Listeria spp. on stainless steel, polyvinyl chloride (PVC), and sealed concrete surfaces. For LE candidate method 1, samples were enriched in FoodChek Actero Listeria Enrichment Media [ALEM; Performance Tested MethodSM (PTM) 111201] at 35 ± 2°C for 18 to 24 h and evaluated for a range of analytical sample volumes. For LE candidate method 2, the current Roka PTM using 90 mL of Half-Fraser broth for enrichment at 35 ± 2°C was evaluated at 24 h with a reduced sample volume. These comparisons were made in multiple studies across the three environmental surfaces. Within each method and study, a total of 5 samples were uninoculated, 20 samples were inoculated with Listeria spp. at a low level to target fractional positivity, and 5 samples were inoculated with Listeria spp. at a high level to approach a probability of detection of 1. Inclusivity and exclusivity studies were also conducted for the LE method in combination with Half-Fraser and ALEM. The Atlas Listeria Environmental LE Detection Assay detected all 50 inclusive organisms, including 25 strains of L. monocytogenes and 5 strains of each of the other five common species of Listeria (L. innocua, L. welshimeri, L. ivanovii, L. seeligeri, and L. grayi) and none of the 30 exclusive organisms across all media and with both 200 and 2000 µL sample volumes. For the LE candidate method 1 studies, no significant differences were observed within the Roka ALEM method at 18, 20, or 24 h and for both the 200 and 2000 µL sample volumes as compared with the paired culture outcome. However, the ALEM method performed significantly better as compared with the unpaired reference method for sealed concrete and stainless steel. For the LE candidate method 2 studies, no significant differences were observed within the Roka HF method at 24 h for the 200 and 2000 µL samples as compared with the paired culture outcomes and unpaired reference method outcomes across the surfaces. The independent laboratory studies observed no significant differences in performance between the USDA/MLG 8.09 reference method and candidate methods 1 or 2, respectively, across the evaluated parameters. Overall, the candidate method 1 modification parameters and candidate method 2 sample parameters for the Atlas Listeria Environmental LE Detection Assay were statistically equivalent to or better than the reference method for detection of Listeria spp. on stainless steel, PVC, and sealed concrete surfaces, providing greater flexibility in method application for end users.

Atlas Salmonella detection method using transcription mediated amplification (TMA) to detect Salmonella enterica in a variety of foods and select surfaces.

The Atlas Salmonella detection assay was compared to the reference culture methods for 12 foods and three surfaces. Comparison of the Atlas method to the U.S. Food and Drug Administration Bacteriological Analytical Manual (FDA/BAM) and U.S. Department of Agriculture-Food Safety and Inspection Service/Microbiology Laboratory Guidebook (USDA-FSIS/MLG) reference methods required an unpaired approach. Each method had a total of 320 samples inoculated with an S. enterica strain. Each food and surface was inoculated with a different strain of S. enterica at two different levels/ method. Meat and egg products were compared to the USDA-FSIS/MLG 4.05 method. All other foods were compared to the FDA/BAM-5 method. The Atlas method had 148 positives out of 320 total inoculated samples, compared to 119 positives for the reference methods. Overall, the probability of detection analysis of the results showed equivalent or better performance by the Atlas Salmonella detection method compared to the reference methods. The Atlas Salmonella detection assay detected all 100 inclusive organisms and none of the 30 exclusive organisms. The lot-to-lot and kit stability studies showed no statistical differences between lots or over the term of the shelf-life. Instrument-to-instrument testing showed no statistical difference between instruments. Finally, the robustness study showed no difference when the sample volume added to the Atlas Salmonella detection assay varied by 10%, storage time was extended up to 5 days before analysis, or enrichment times were varied from 12 to 24 h.

Roka Listeria detection method using transcription mediated amplification to detect Listeria species in select foods and surfaces. Performance Tested Method(SM) 011201.

The Roka Listeria Detection Assay was compared to the reference culture methods for nine select foods and three select surfaces. The Roka method used Half-Fraser Broth for enrichment at 35 +/- 2 degrees C for 24-28 h. Comparison of Roka's method to reference methods requires an unpaired approach. Each method had a total of 545 samples inoculated with a Listeria strain. Each food and surface was inoculated with a different strain of Listeria at two different levels per method. For the dairy products (Brie cheese, whole milk, and ice cream), our method was compared to AOAC Official Method(SM) 993.12. For the ready-to-eat meats (deli chicken, cured ham, chicken salad, and hot dogs) and environmental surfaces (sealed concrete, stainless steel, and plastic), these samples were compared to the U.S. Department of Agriculture/Food Safety and Inspection Service-Microbiology Laboratory Guidebook (USDA/FSIS-MLG) method MLG 8.07. Cold-smoked salmon and romaine lettuce were compared to the U.S. Food and Drug Administration/Bacteriological Analytical Manual, Chapter 10 (FDA/BAM) method. Roka's method had 358 positives out of 545 total inoculated samples compared to 332 positive for the reference methods. Overall the probability of detection analysis of the results showed better or equivalent performance compared to the reference methods.