Molecular epidemiology of Salmonella Typhimurium and Salmonella 4,5,12:i:- isolated from pig farms in Spain.

The genetic diversity of 194 salmonella ISolates belonging to different phagetypes of S. Typhimurium and S 4,5, 12:i- 1solated from both healthy slaughter (157) and diarrhoea-affected (37) p1gs was assessed usmg molecular typing (plasmid profiling and PFGE). The aim of this study was to elucidate the sources of Infection, and to follow the spread of specific clones w1thm the infected farms. In spite of the genetic diversity observed amongst the Isolates, some clones were more prevalent and widely distributed in the pig population, being detected in several slaughter batches from the same and different farms. This finding suggests the existence of multiple and recurrent infection sources, as well as mechanisms favouring survival, persistence and spreading of certam clones within and between pig farms