Evaluation of the CERTUS Environmental Listeria Species Detection Kit for the Detection of Listeria Species on Environmental Surfaces: AOAC Performance Tested MethodSM 101802.

BACKGROUND: CERTUS Environmental Listeria species Detection Kit (CERTUS EL Detection Kit) is a real-time, bio-contained assay designed to accurately detect Listeria species (L. grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. seeligeri, and L. welshimeri) from environmental surface matrixes using an antibody-coupled magnetic microparticle with a Surface Enhanced Raman Spectroscopy (SERS) nanoparticle technology test system paired with proprietary CERTUS EL Selective Growth Media and CERTUS Detection Unit. OBJECTIVE: The method was evaluated for AOAC®Performance Tested MethodSM certification. METHODS: Inclusivity and exclusivity, matrix studies, product consistency and stability were conducted to evaluate the CERTUS EL Detection Kit. RESULTS: In the matrix studies, stainless steel, ceramic tile, plastic (polystyrene) and sealed concrete environmental surfaces (4 × 4" test areas) were tested. No statistically significant differences were found by Probability of Detection analysis (POD) in any of the matrixes when results were compared to the U.S. Food and Drug Administration cultural microbiology reference method for Listeria. The CERTUS EL Detection Kit correctly identified all 50 target Listeria isolates and correctly excluded all 30 non-target strains that were analyzed. Probability of Detection analysis of CERTUS EL Detection Kit robustness, product consistency (lot-to-lot) and stability studies demonstrated no statistically significant differences, and no variation was observed between instruments. CONCLUSIONS: The data collected in these studies demonstrate that the CERTUS EL Detection Kit is a reliable method for the rapid and specific detection of Listeria from stainless steel, ceramic tile, plastic (polystyrene) and sealed concrete environmental surfaces.

Validation of Solus One Salmonella from Select Food Matrixes and Stainless-Steel and Plastic Environmental Surfaces.

Background: Solus One Salmonella is designed to accurately detect Salmonella species (Salmonella enterica subspecies enterica, salamae, arizonae, diarizonae, houtenae, indica, and Salmonella bongori) from select food matrixes and stainless-steel and plastic environmental surfaces. Solus One Salmonella uses an antibody-based technology test system that is paired with media and our proprietary media supplement, the Solus One Salmonella supplement combined with a manual or automated sample preparation method. Objective: Solus One Salmonella was evaluated for inclusivity and exclusivity, and a matrix comparison study was done for six food matrixes (raw beef trim, pasteurized liquid egg, raw salmon, cheddar cheese, Romaine lettuce, nonfat dry milk) and two environmental surfaces (stainless steel and polystyrene). Methods: Solus One Salmonella was compared with the U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 5: Salmonella (July 2018) and the U.S. Department of Agriculture Food Safety and Inspection Service Microbiology Laboratory Manual, 4.09 (January 2017) in the matrix study. Both the manual and automated sample preparation methods were performed for cheddar cheese and stainless-steel environmental surfaces. Results: For the inclusivity and exclusivity evaluation, Solus One Salmonella correctly detected all 108 target organism isolates and correctly excluded all 35 nontarget strains that were analyzed. Conclusions: In the method comparison study, both Solus One Salmonella manual and automated sample preparation methods demonstrated no significant differences based on probability of detection (POD) statistical analysis between presumptive and confirmed results or between candidate and reference method results for the six food matrixes after 20-22 h and two environmental surfaces after 16-20 h of enrichment time. POD analysis of Solus One Salmonella method robustness, product consistency, and stability studies using the automated sample preparation method demonstrated no statistically significant differences.

Evaluation of the Solus One Listeria Method for the Detection of Listeria Species on Environmental Surfaces.

Background: Solus One Listeria is designed to accurately detect Listeria species (Listeria grayi, L. innocua, L. ivanovii, L. marthii, L. monocytogenes, L. seeligeri, and L. welshimeri) from stainless steel and plastic environmental surface matrixes using an antibody-based technology test system paired with proprietary SOLO+ media and combined with manual or automated sample preparation method. Objective: Solus One Listeria was evaluated for inclusivity and exclusivity and a matrix comparison study for two environmental surfaces. Methods: Solus One Listeria was compared with the following reference method for the method comparison study: the U.S. Food and Drug Administration Bacteriological Analytical Manual Chapter 10 from stainless steel and plastic environmental surfaces. Both the manual and automated preparation methods were performed for stainless steel and plastic environmental surfaces. Results: For the inclusivity and exclusivity evaluation, Solus One Listeria correctly identified all 50 target organism isolates and correctly excluded all 30 nontarget strains that were analyzed. In the method comparison study, both Solus One Listeria manual and automated preparation methods demonstrated no significant differences based on probability of detection statistical analysis between presumptive and confirmed results or between candidate and reference method results for two environmental surfaces after 22-30 h of enrichment time. Probability of detection analysis of Solus One Listeria method robustness, product consistency (lot-to-lot), and stability studies using the automated preparation method demonstrated no statistically significant differences. Conclusions: The data from the study support the product claims of Solus One Listeria for the accurate detection of Listeria species, using both the manual and automated methods (using the Dynex DS2 instrument), on both environmental surfaces analyzed.

Active control of vortex shedding: an explanation of the gain window.

This paper explains the gain window phenomenon seen in early experimental and computational studies on active, closed-loop control of vortex shedding, whereby shedding is completely suppressed only if the feedback gain lies within some narrow window of stabilizing gains. Using two-dimensional direct numerical simulations and reduced-order modeling techniques, a low-order, linear model of the cylinder wake is formed at a Reynolds number of 60. This model is used to reproduce and to explain the gain window seen in previous studies. It is shown that the gain window is not caused by the destabilization of a higher mode but rather is determined entirely by the behavior of the open-loop unstable mode under the action of the closed-loop controller. It is demonstrated that the time taken for actuated fluid to convect to the sensor location plays an important part in explaining this gain window. A similar analysis at a higher Reynolds number of 80 reveals that the wake remains unstable for all choices of the feedback gain. The study illustrates the limitations of closed-loop suppression of vortex shedding when a very simple control strategy is used.