Moller, K *, and Ahrens, P
Danish Veterinary Laboratory, Copenhagen, Denmark

Serpulina pilosicoli has recently been identified as the agent of porcine spirochetosis. To investigate the genetic diversity, amplified fragment length polymorphism (AFLP) and pulsed-field gel electrophoresis (PFGE) were applied on 25 Danish field isolates. While PFGE yielded 12-15 bands, AFLP showed up to 50 bands, which were easily differentiated by applying automatic reading of gels as used for sequence determinations. Both techniques were highly sensitive, each differentiating the isolates into more than 20 groups. Dendograms showed from 40 to 100% similarity between the isolates. These results confirm the considerable heterogeneity amongst S.pilosicoli isolates. Generally, 100% similarity was only seen among isolates from one herd, indicating a stable colonization by this organism. Compared to PFGE, the workload of AFLP is much lower and future studies of the genetic diversity of porcine spirochaetes should comprise this technique.