Development and Evaluation of a Real-Time PCR Assay for Salmonella Detection

Introduction: Salmonella is found in many food and environmental sources, and it can cause serious illness. In the presence of competing flora, culture isolation may require lengthy procedures with skilled interpretation. Rapid, non-culture methods, such as those based on PCR, can provide for fast and accurate detection. The incorporation of real-time PCR detection into the current commercial BAX® System assay shortens the overall time to result with no loss in performance.

Purpose: The purpose of this study was to characterize the performance of the newly developed real-time PCR assay for genus Salmonella detection. Inclusivity and exclusivity of the new assay were compared to the commercial Salmonella assay, and sensitivity was determined in the presence of a variety of food types.

Methods: Studies evaluating the sensitivity of the new real-time assay were conducted using titrations of target cells inoculated into negative food enrichments. Cell lysates were also used to conduct inclusivity and exclusivity studies for the new real-time assay.

Results: The sensitivity of the assay was determined to be 1X10⁴ cfu/ml for each of the six Salmonella enterica subgenera as well as the species Salmonella bongori. The assay was 100% inclusive for all 409 Salmonella strains tested and 100% exclusive for all 44 non-Salmonella bacteria tested.

Significance: The new real-time PCR assay for Salmonella provides reduced processing time (65 minutes) with no change in sensitivity, inclusivity or exclusivity performance. This improved productivity will allow food manufacturers to make earlier, confident decisions regarding Salmonella presence in their products.