Studies on Erysipelothrix insidiosa S. rhusiopathiae. 1. Morphology, cultural features, biochemical reactions and virulence.

Sixty-two E. insidiosa strains isolated from joints or regional lymph nodes of pigs were examined from the point of view of morphology, cultural aspects, biochemical activity and virulence. All the strains consisted of gram-positive, short rods, which were similar on solid and fluid media. All strains formed H2S. Otherwise the biochemical activity was rather low except in 1 strain (no. 18), which was very active. One strain (no. 36) was rather inactive, since it showed no other activity than H2S formation. This latter strain was the only one that was avirulent for mice. The rest of the strains (61) were strongly virulent for mice (LD50 0.5 × 10−4.17 to 0.5 × 10−8.5). Of 7 strains examined for virulence for pigs by intracutaneous injection of 0.1 ml broth culture, 6 were virulent. The 7th, which was avirulent, was the one that was also avirulent for mice.