Numerical taxonomy of Clostridium botulinum and Clostridium sporogenes strains, and their susceptibilities to induced lysins and to mitomycin C.

Abstract

An attempt to classify fourteen strains of Clostridium sporogenes and thirty strains of Clostridium botulinum types A, B, C, D, E, and F by numerical taxonomy was made. All proteolytic strains of C. botulinum types A, B, and F and C. sporogenes were classified in the phenon I at a level of 86% S-value. In the phenon I, these strains coexisted in a mixed-up fashion, irrespective of conventional species or type of bacteria. A concentrated lysin solution, which was prepared from an induced lysate of a C. botulinum A190 culture, lysed vegetative cells of all proteolytic C. botulinum and C. sporogenes strains classified in the phenon I, but did not lyse the cells of the other Clostridia. However, cells of nonproteolytic C. botulinum F-OSU and four out of five strains of Clostridium tetani were lysed by the concentrated lysin to a limited extent. The phenon II contained all nonproteolytic strains of C. botulinum B, C, D, E, and F, which were mutually linked with S values of more than 85%. Strains of Clostridium histolyticum used as a reference group formed the phenon III. Any strain grouped in one phenon was differentiated from strains grouped in the other phenons by low S-values, that were less than 77%. A striking difference in the number of strains susceptible to mitomycin C was demonstrated between C. botulinum and C. sporogenes. In all thirty-five cultures, except four substrains of C. botulinum B-NIH, of proteolytic and nonproteolytic C. botulinum, bacterial lysis was consistently induced by the treatment of 1 μg per ml of mitomycin C, while only four out of thirty-seven C. sporogenes strains were as sensitive to mitomycin C as C. botulinum. Toxigenic substrains of C. botulinum B-NIH, NIH15 and NIH19, were sensitive to mitomycin C, but nontoxigenic strains, NIH5, and NIH-NP, were not.