Improvement of strain discrimination by combination of RAPD with PFGE for the analysis of the swine isolates of Salmonella enterica serovar Choleraesuis

Salmonella enterica serovar Choleraesuis (S. Choleraesuis) can cause salmonellosis in pigs and humans. Currently, the most common method used for the subtyping of this Salmonella serovar is pulsed field gel electrophoresis (PFGE) using XbaI as a DNA digestion enzyme. In this study, we compared and combined PFGE with the randomly amplified polymorphic DNA method, for the typing of 95 S. Choloraesuis strains isolated from diseased pigs. Using PFGE with XbaI, with AvrII, and with SpeI digested DNA, 29, 74, and 40 patterns, respectively, were obtained. Also, 53, 15, and 35 strains, respectively, belong to the major patterns X1, A1, and S1. When these three digestion patterns were combined, 83 PFGE pattern combinations were obtained. On the other hand, using RAPD with selected primer alone generated 76 patterns, and 11 strains which fell within a single X1A1S1 PFGE combination pattern were discriminated into 10 patterns. Thus, for S. Choloraesuis, PFGE with AvrII allowed higher discrimination than PFGE with XbaI, and some of the PFGE groupings obtained by combining the XbaI, AvrII and SpeI digestion patterns were further subdivided by the RAPD method.