Persistence of a Salmonella enterica serotype Typhimurium clone in Danish pig production units and farmhouse environment studied by pulsed field gel electrophoresis (PFGE)

The clonal relationship among Salmonella enterica serotype Typhimurium isol ates from selected pig production units in Denmark was investigated by the pulsed field gel electrophoresis (PFGE) typing method to determine environm ental survival and spread of Salmonella in different herds. Thirty-four Typ himurium isolated during 1996-1998 from porcine faeces and environmental sa mples from three pig farms designated I, 3 and 5 were characterised by PFGE using two restriction enzymes. Farm 5 supplied piglets to farm 1 and the h erds were located close to each other. Results of PFGE analysis showed both intra- and inter-relationships, i.e. identical PFGE patterns among the fae cal and environmental isolates from farm 1 and farm 5. All the isolates fro m farm 3 irrespective of the source showed identical PFGE patterns, but wer e different From samples from farms 1 and 5. This study indicates spread be tween Farms and survival of a farm-specific clone. Furthermore: identical P FGE patterns of isolates from piglet supplier and Finisher herds indicate t hat the farrow-to-grower herd of farm 5 was sub-clinically infected prior t o delivery to farm I and thereby caused the transmission of Salmonella. (C) 2000 Federation of European Microbiological Societies. Published by Elsevi er Science B.V. All rights reserved.