Rapid Detection and Quantification of Salmonella enterica in Peanut Butter by a rRNA Detection System

Introduction: Methods for rapid and reliable detection and quantification of microorganisms and pathogens in food, beverages and water are receiving increasing attention. The sandwich hybridization method used in the rRNA Detection System is a suitable alternative for such analysis. This test method is independent of the influence of sample matrices, and is able to distinguish between live and dead cells. Furthermore, the detection of non-culturable microbes is possible. This test performed in less than 3 hours (in addition to the prep time), offers a significant time savings compared to cultivation-based assays.

Purpose: Rapid detection and quantification of pathogens like Salmonella enterica for economical and safe production of food and beverages.

Methods: Salmonella enterica subsp. enterica (ATTC 13311) was detected by the use of HybriScanD Salmonella Test. The method is based on molecular genetic identification allowing detection of a group of microorganisms as well as specific species. No PCR is required because the method is quantitative without cell counting (using standards) and uses standard laboratory equipment. The signal read-out is triggered optically by an enzymatically generated color change. Peanut Butter sample matrix (9 different brand codes with 12 different code dates) was examined. Peanut butter samples inoculated with Salmonella enterica were tested along with a control. All samples and the negative controls were tested and verified for Salmonella according to EN ISO 6579:2002.

Results: Out of 107 Salmonella enterica inoculated peanut butter samples, 106 were identified as clearly contaminated with Salmonella by the use of HybriScanD Salmonella assay. The result of 1 sample was considered questionable. All negative controls gave negative results in the HybriScanD Salmonella assay. 1-5 CFU of Salmonella spp. in 25 g Peanut Butter can be positively identified by HybriScanD Salmonella assay after 24 hours enrichment time. Results have shown the possibility to shorten the enrichment time of pre-and main culture for the HybriScanD Salmonella Test from 42 hours to a total of 24 hours for Peanut Butter matrix.

Significance: HybriScan rRNS Detection System is an economical, high throughput, 96-well microplate format system. The test is performed in less than 3 hours (in addition to the prep time) and offers a significant time savings compared to cultivation-based assays.