Study validates disc diffusion method to sort vaccine and field Salmonella

Vaccination remains a cornerstone of Salmonella control in poultry, but a practical problem has persisted for years: when a flock tests positive, labs need to know quickly whether they’re seeing a vaccine strain or a field strain. A new paper in Veterinary Sciences reports a multi-supplier validation of a disc diffusion method designed to reliably distinguish a bivalent live Salmonella vaccine from field isolates of Salmonella Enteritidis and Salmonella Typhimurium, the two serovars most closely tied to poultry-associated human salmonellosis. That matters because international guidance already stresses that when live Salmonella vaccines are used, vaccine and field strains should be easily differentiated in the lab. (woah.org)

Why it matters: For veterinary professionals and poultry health teams, a validated, lower-complexity phenotypic method could help avoid false alarms, unnecessary control actions, and confusion during surveillance or outbreak workups. The broader industry context supports the need: live attenuated Salmonella vaccines are widely used in poultry, but vaccine-origin strains can persist in production environments, and misclassification can trigger economic losses or inappropriate responses. Other groups have pursued PCR-based DIVA tools for the same reason, including assays that aim to prevent unnecessary culling and speed decisions, but those methods may not be as accessible to every laboratory. (pmc.ncbi.nlm.nih.gov)

What to watch: The next question is whether this disc diffusion approach is adopted broadly in routine surveillance, or whether molecular DIVA assays continue to set the pace for faster, strain-specific differentiation. (mdpi.com)