A Novel Multiplex Real-Time PCR Method for Rapid Detection and Serotyping of Salmonella Enteritidis and Typhimurium

Introduction: In Europe, food regulation was recently reinforced to prevent poultry meats adulterated with either S. Enteritidis or S. Typhimurium from being marketed. While the current Kauffmann-White serotyping method requires 4/5 days to assess the presence of these pathogens, a new method was developed as an alternative, single-tube real-time PCR method allowing their simultaneous and specific detection within two days. 

Purpose: This study aimed at evaluating the performances of the iQ-Check Salmonella E&T kit on food and environmental samples, the detection limits (LD), and the specificity.

Methods: Twenty-three samples were artificially spiked with low amounts of either Salmonella Enteritidis or Typhimurium and subjected in parallel to both iQ-Check Salmonella E&T  and iQ-Check Salmonella II methods. For LD, genomic DNA was extracted from pure strains and its concentration evaluated by OD_{260 nm} . Serial dilutions were subsequently assayed by PCR.  For inclusivity study, 45 Salmonella Enteritidis and Typhimurium strains were tested.

Results: All 23 spiked samples yielded positive results. Detection limit was estimated between 2 and 10 genome units per PCR well for both serotypes. Inclusivity was validated on all 19 Salmonella Enteritidis and 26 Salmonella Typhimurium strains.

Significance: The test allows a faster release of the products and the reduction of the number of samples to be confirmed by the standard method. Additional evaluations are currently ongoing in different laboratories. The method will also allow the detection of the Salmonella Enteritidis serovar only, to better address the needs of the US eggs industry.