Study validates disc diffusion method for Salmonella vaccine strains

A new validation 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 in poultry diagnostics. That matters because live vaccines are widely used in breeding and laying hens, but when a flock tests positive, laboratories and regulators need to know quickly whether they’re seeing a vaccine strain or a true field infection. The broader regulatory backdrop is clear: international guidance says live vaccine and field strains should be easy to differentiate in the laboratory, and prior work around Ceva’s Salmovac/Cevac Salmovac 440 platform has shown that faster differentiation can shorten the time producers, veterinarians, and authorities wait for decisions on movement, egg marketing, and follow-up testing. (woah.org)

Why it matters: For veterinary professionals, this is less about a new vaccine than about a practical diagnostics question. A validated, lower-complexity phenotypic method could help poultry labs confirm whether a positive isolate is vaccine-related without relying only on more specialized molecular workflows. That can support flock-level decision-making, reduce unnecessary disruption after routine surveillance positives, and strengthen confidence in vaccination programs that are central to Salmonella control and food safety. Related studies have reported 100% agreement for alternative differentiation approaches, including chromogenic media for the 441/014 vaccine strain and RT-PCR assays for AviPro vaccine strains, underscoring how much the sector values accurate DIVA-style tools. (pmc.ncbi.nlm.nih.gov)

What to watch: Watch for whether the disc diffusion approach is adopted by reference and commercial poultry laboratories, and whether regulators or vaccine suppliers move to incorporate it into routine Salmonella surveillance workflows. (pmc.ncbi.nlm.nih.gov)