Study validates disc diffusion test for Salmonella vaccine strains

A new study in Veterinary Sciences reports that a simple disc diffusion method can reliably distinguish a bivalent live Salmonella vaccine strain from field strains of Salmonella Enteritidis and Salmonella Typhimurium across multiple suppliers. The paper, by Benjamin Bertin, Marie-Hélène Bayon-Auboyer, and Mustapha Fellag, addresses a practical problem in poultry diagnostics: when live vaccination is widely used, labs need a fast way to tell whether a positive isolate reflects vaccine exposure or a true field infection. The study adds validation for an approach based on antimicrobial susceptibility patterns, rather than relying only on more specialized molecular testing. (pmc.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals working with poultry flocks, that distinction can affect surveillance decisions, reporting, and flock management. EU control programs continue to focus heavily on S. Enteritidis and S. Typhimurium, and vaccine strains are treated differently from relevant field strains in monitoring frameworks. A practical, multi-supplier method could help diagnostic laboratories and poultry veterinarians reduce false alarms, avoid unnecessary restrictions, and move more quickly when true field strains are detected. (food.ec.europa.eu)

What to watch: Watch for whether this method is adopted into routine poultry diagnostic workflows, or paired with PCR-based DIVA testing as labs refine how they confirm vaccine-versus-field isolates. (pmc.ncbi.nlm.nih.gov)