Occurrence and spread of multiresistant Salmonella Typhimurium DT104 in Danish animal herds investigated by the use of DNA typing and spatio-temporal analysis

Abstract

In the investigation we report the occurrence and spread of multiresistant Salmonella Typhimurium phage type (DT) 104 in 174 known Danish animal herds infected between 1996 and 2003. We applied PFGE, plasmid analysis and spatio-temporal analysis for a description of the development and spread of infection among herds. The results showed that in Denmark DT104 are mainly spread by trade of animals; however, horizontal spread of DT104 is also important and the risk of an animal herd becoming infected increased with the proximity in time and space to a DT104-infected herd. Based on these results, it is recommended that specific actions are taken to limit the risk of horizontal spread of DT104 from newly infected herds.

Fig. 1

PFGE types by the use of (a) BlnI and (b) XbaI. (a) Lane 1, size marker (lambda ladder); lane 2, CDC PFGE marker (digested by XbaI); lane 3, PFGE type B1; lane 4, PFGE type B2; lane 5, PFGE type B3; lane 6, PFGE type B4; lane 7, PFGE type B5; lane 8, PFGE type B6; lane 9, PFGE type B7; lane 10, lambda ladder. (b) Lane 1, size marker (lambda ladder); lane 2, CDC marker; lane 3, PFGE type X1; lane 4, PFGE type X2; lane 5, PFGE type X3; lane 6, PFGE type X4; lane 7, PFGE type X5; lane 8, PFGE type X6; lane 9, PFGE type X7; lane 10, PFGE type X8; lane 11, lambda ladder.

Fig. 2

The location of DT104-infected herds in Denmark 1996–2002. △, Pigs (n=137); ○, pigs and cattle (n=10); □, cattle (n=22), ◊, other (n=5).

Fig. 3

The cumulative distribution of the distance between herds (for ‘non-epidemiologically related herds’ only herds infected within a time-frame of 6 months between the infections are included). ○, All herds; +, non-epidemiologically related herds.