Variation in hemolytic activity of Brachyspira hyodysenteriae strains from pigs

Abstract

Brachyspira hyodysenteriae is the primary cause of swine dysentery, which is responsible for major economic losses to the pig industry worldwide. The hemolytic activity of 10 B. hyodysenteriae strains isolated from stools of pigs with mild to mucohemorrhagic diarrhea was compared and seven hemolysis associated genes were sequenced. Hemolysis induced by these strains varied from strong to near absent. One weakly hemolytic B. hyodysenteriae strain showed sequence changes in five hemolysis associated genes (tlyA, tlyB, hemolysin III, hemolysin activation protein and hemolysin III channel protein) resulting in amino acid substitutions. The occurrence of weakly hemolytic strains identifiable as B. hyodysenteriae should be taken into account in swine dysentery diagnostics. The presence of these strains may affect herd dysentery status, with great impact on a farms trading opportunities.

Figure 1

Dendrogram based on the concatenated sequence (4086 bp) of the 7 MLST genes of B. hyodysenteriae and B. intermedia. The alignment was created using clustalw, for the dendrogram distance calculation (Kimura) and UPGMA were used (PHYLIP). Bootstrap values greater than 60 are shown in the nodes. Scale bar indicates a distance of 1 substitution in 100 nt.

Figure 2

In vitro hemolytic capacity of B. hyodysenteriae strains used in this study. Hemolysis is represented by the mean value of absorption at 450 nm after incubation of red blood cell suspension with supernatant of the different B. hyodysenteriae identifiable strains. PC, positive control; NC, negative control. Significant differences between B. hyodysenteriae identifiable strains and reference strain B204 are indicated,* P < 0.01.