The capsules of Corynebacterium equi and Streptococcus equi

The capsules of Corynebacterium equi and Streptococcus equi were examined by electron microscopy after staining with ruthenium red. They were compared with the capsule of Klebsiella pneumoniae which had previously been examined using the same procedure (Springer & Roth, 1973). The capsule of C. equi had a laminated appearance. When S. equi was grown on solid medium, its capsule appeared as radially arranged projections capped by a thick electron dense layer. When grown in liquid medium, S. equi produced a capsule which showed as short thick projections with no layer external to them.