Rapid detection and classification of Salmonella enterica shedding in feedlot cattle utilizing Roka Bioscience Atlas Salmonella detection assay for the analysis of rectoanal mucosal swabs

Authors: CHANEY, W EVAN - Roka Bioscience Inc; Agga, Getahun; Nguyen, Scott; Arthur, Terrance; Bosilevac, Joseph - Mick; DREYLING, ERIN - Roka Bioscience Inc; RISHI, ANANTHARAMA - Roka Bioscience Inc; Harhay, Dayna

Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/25/2017
Publication Date: 9/18/2017
Publication URL: http://handle.nal.usda.gov/10113/5852142
Citation: Chaney, W.E, Agga, G.E., Nguyen, S.V., Arthur, T.M., Bosilevac, J.M., Dreyling, E., Rishi, A., Brichta-Harhay, D. 2017. Rapid detection and classification of Salmonella enterica shedding in feedlot cattle utilizing Roka Bioscience Atlas Salmonella detection assay for the analysis of rectoanal mucosal swabs. Journal of Food Protection. 80(10):1760-1767. https://doi.org/10.4315/0362-028X.JFP-17-124.

Interpretive Summary: Cattle are recognized carriers of the foodborne pathogen Salmonella enterica, and fecal shedding of this organism poses a potential human health risk through possible contamination of beef at harvest, or produce through environmental contamination sources. Recognition of these potential contamination sources has resulted in an increasing focus on pre-harvest food safety, and the need for rapid methods for the detection and quantification of foodborne pathogens such as Salmonella enterica in beef cattle. Thus, the objective of this study was to validate the Atlas Salmonella SEN detection assay for the detection of S. enterica with and without sample enrichment. Further, the ability of the assay to classify animals as “high” or “non-high” shedders was assessed. Results showed the Atlas method was 100% sensitive and specific for the detection of Salmonella from enriched cattle fecal swab samples, and established an optimum cutoff value to classify high shedders of Salmonella from fecal swab samples of feedlot cattle. Moreover, the ease of use and decreased turnaround time to results in comparison with traditional culture based methods suggests that use of this or similar assays holds the potential to revolutionize on farm surveillance of cattle herds for Salmonella carriage and provide valuable data needed for the development of Salmonella pre-harvest mitigation strategies.

Technical Abstract: With an increasing focus on preharvest food safety, rapid methods are required for the detection and quantification of foodborne pathogens such as Salmonella enterica in beef cattle. We validated the Atlas Salmonella Detection Assay (SEN), a nucleic acid amplification technology that targets Salmonella rRNA, for the qualitative detection of S. enterica with sample enrichment using immunomagnetic separation as a reference test, and we further evaluated its accuracy to predict pathogen load using SEN signal-to-cutoff (SCO) values from unenriched samples to classify animals as high or nonhigh shedders. Rectoanal mucosal swabs (RAMS) were collected from 238 beef cattle from five cohorts located in the Midwest or southern High Plains of the United States between July 2015 and April 2016. Unenriched RAMS samples were used for the enumeration and SEN SCO analyses. Enriched samples were tested using SEN and immunomagnetic separation methods for the detection of Salmonella. The SEN method was 100% sensitive and specific for the detection of Salmonella from the enriched RAMS samples. A SEN SCO value of 8, with a sensitivity of 93.5% and specificity of 94.3%, was found to be an optimum cutoff value for classifying animals as high or nonhigh shedders from the unenriched RAMS samples. The SEN assay is a rapid and reliable method for the qualitative detection and categorization of the shedding load of Salmonella from RAMS in feedlot cattle.