Detection of capsule in strains of Clostridium difficile of varying virulence and toxigenicity.

Nine toxigenic and six non-toxigenic strains of Clostridium difficile, of varying virulence in the hamster model of antibiotic-associated colitis, were examined for the presence of a capsule. Antibody stabilisation of the capsule with heterologous and/or homologous antiserum fixed in glutaraldehyde, or direct fixation in glutaraldehyde/diamine, were used with added ruthenium red to stain the capsular glycocalyx. All strains possessed a capsule which was either loose-knit or compact, sometimes with attached globular masses. Better capsule preservation was achieved in some strains with glutaraldehyde/diamine/ruthenium red fixative than with homologous or heterologous antibody stabilisation. The possession of a capsule following in vitro growth does not appear to correlate with the virulence status of these strains of C. difficile.