Ribotyping as an identification tool for Clostridium botulinum strains causing human botulism

Ribotyping was used for characterisation of 68 Clostridium botulinum strain s and five related Clostridium species to determine the applicability of th is method for identification of species causing human botulism. Thirteen re striction enzymes were initially tested for suitability for ribotyping of C . botulinum, of which EcoRI and HindIII were selected. Both enzymes clearly differentiated between proteolytic (group I) and a nonproteolytic (group I I) strains of C. botulinum, and can be recommended for Group/species identi fication. Using a commercial software package (GelCompar), a numerical anal ysis of the discriminatory abilities of EcoRI and HindIII ribotyping within and between the two C. botulinum groups was performed. EcoRI had the highe r discriminatory index (0.982), but the ribopatterns generated with group I I strains were partly muddled and difficult to interpret. All HindIII ribop atterns were easy to analyse and the discriminatory index for all strains w as almost equally high (0.954), whereas this enzyme did not discriminate we ll between group I isolates. The Clostridium strains diverged at 35+/-13% ( mean+/-standard deviation) Dice similarity in dendrograms based on cluster analysis of the ribotyping results. These findings are in good agreement wi th taxonomical ribotyping studies with other bacterial genera, indicating t hat ribotyping is a highly suitable method for C. botulinum species identif ication. (C) 1999 Elsevier Science B.V. All rights reserved.