A molecular assay for rapidly distinguishing the AviPro SALMONELLA VAC T vaccine strain from wild-type field isolates.

Rapid differentiation of the AviPro Salmonella VAC T strain from wild-type Salmonella ser. Typhimurium isolates is essential for the monitoring of veterinary isolates and targeted control actions. The distinction between the two strain types is routinely made by phenotypic antimicrobial resistance testing, but this sometime leads to ambiguous results with major economic implications. In this study, we used whole-genome sequencing to identify conserved and specific mutations in resistance and virulence genes which enable to distinguish field and vaccine strains. Based on this information, we developed and validated (n = 199) a Luminex-based assay targeting seven specific single-nucleotide polymorphisms. This molecular test is able to distinguish both Salmonella ser. Typhimurium types with 100% sensitivity and specificity within one working day.