Application of variable number of tandem repeat analysis to track Salmonella enterica ssp. enterica serovar Typhimurium infection of pigs reared on three British farms through the production cycle to the abattoir

Aims:  This study investigated the diversity and persistence of Salmonella strains through the pork finishing cycle, from the farm into the abattoir. Methods and Results:  Isolates from four batches of finishers, from farm to abattoir, were used. Salmonella Typhimurium isolates were subjected to molecular typing using pulsed-field gel electrophoresis and variable number of tandem repeat analysis. The results demonstrated that infection was transferred from the farm to the abattoir. Within the abattoir, infection from individual pigs contaminated the exterior of the carcass and pigs exposed to Salmonella in the lairage were infected. Conclusions: Salmonella can be introduced at various points in the pig production and slaughter process. Carcass contamination may arise from infection on farm and exposure in the lairage and abattoir environment. Pigs could be contaminated by previous batches of pigs while in lairage or during the dressing process. Salmonella infection on farms is dynamic with multiple serovars present from different sources. Significance and Impact of the Study:  Molecular typing methods facilitated the tracing of Salm. Typhimurium through the production cycle and differentiated some farm-acquired from abattoir-acquired strains. The findings emphasize the importance of integrated control strategies along the pork food chain.