Level 2 Modification (Matrix Extension) Study of the Neogen® Molecular Detection Assay 2 - Salmonella Enteritidis/Salmonella Typhimurium Method: Detection of Salmonella enterica ser. Enteritidis and Salmonella enterica ser. Typhimurium in Cooked Breaded Chicken and Raw Ground Chicken (25 g).

Background: The Neogen® Molecular Detection Assay 2-Salmonella Enteritidis/Salmonella Typhimurium (MDA2-SE/ST) method is a nucleic acid amplification test for specific detection of Salmonella enterica ser. Enteritidis (SE) and Salmonella enterica ser. Typhimurium (ST), including the ST monophasic variant Salmonella enterica  1,4,[5],12:i:-, in select poultry samples. Results for SE and ST are generated separately. The method was previously validated for testing of chicken carcass rinse and raw ground chicken (325 g).

Objective: The objective of the study was to validate the MDA2-SE/ST method for detection of SE and ST in cooked breaded chicken and raw ground chicken (25 g) as a Level 2 modification for Performance Tested Methods  SM certification.

Methods: Inclusivity/exclusivity testing and independent laboratory testing of cooked breaded chicken and raw ground chicken (25 g) were conducted.

Results: In inclusivity testing with BPW-ISO broth at 41.5 °C, all 50 SE strains produced positive results in the SE assay and negative results in the ST assay. All 53 ST strains (including the monophasic variant) produced positive results in the ST assay and negative results in the SE assay. All 35 exclusivity strains produced negative results in both assays. The exclusivity panel included multiple non-SE group D1  Salmonella serovars, multiple non-ST group B serovars, Salmonella spp. from other somatic groups, and other Enterobacteriaceae. In matrix testing, there were no significant differences in the number of positive results obtained with the MDA2-SE/ST and reference methods by probability of detection analysis at the 95% confidence level.

Conclusions: Results of the matrix extension study showed that the MDA2-SE/ST method is an accurate method for detection of SE and ST in cooked breaded chicken and raw ground chicken (25 g).

Highlights: Validation of the MDA2-SE/ST method for two additional matrixes provides users with additional capability for specific detection of SE and ST in poultry products.