Purpose: These studies were conducted to develop a semi-quantitative, threshold-based testing application for a qualitative molecular detection technology.
Methods: Three phases of study were conducted to optimize detection of 0.5 and 1 CFU/g Salmonella contamination levels in raw ground turkey within the time frame of one production shift utilizing the Atlas Salmonella SEN Detection Assay. Studies consisted of replicate (n = 10 - 15) 375 g ground turkey samples inoculated with one of 5 levels of a 5-serovar Salmonella enterica cocktail (Newport, Hadar, Heidelberg, Typhimurium and St. Paul) for each experimental combination of contamination level, enrichment ratio, temperature and sampling time point. Phase 1 evaluated enrichment of 375 g samples in BPW at 1:1, 1:2 and 1:3 ratios at 35° and 42°C for 3 and 4 hours. Phase 2 optimized enrichment time and temperature to within half hour intervals and guard-banded conditions selected in phase 1. Phase 3 served to validate the application sampling parameters demonstrating repeatability. Ten replicate samples were evaluated for each experimental combination in triplicate studies. In all studies, mean relative light units were used as the semi-quantitative measurable response variable.
Results: Sampling parameters were established for a threshold based testing application to accurately detect 1 CFU/g contamination levels of Salmonella in 375 g ground turkey samples within one working shift and with 100% confidence.
Significance: This threshold based testing application provides an additional tool for process control and intervention, in combination with appropriate diversion, to reduce Salmonella enterica burden entering commerce.