Fluorescent-antibody reagents for the identification of Clostridium botulinum

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Abstract
Fluorescent-antibody reagents were prepared against vegetative cells of representative strains of each physiological group and toxin type of C. botulinum known to have caused botulism in humans. A fluorescent-antibody reagent was also prepared for C. botulinum type G, which has been isolated from autopsy specimens but which has not clearly been implicated in botulism. These fluorescent-antibody reagents were evaluated against 200 strains of C. botulinum and 64 strains of other clostridia. Each reagent reacted with at least a 2+ intensity with all of the strains in its same toxin type and physiological group. Of the strains, 97% gave at least a 3+ reaction with the homologous group or toxin type reagent. Some cross-reactions occurred with reagents against different toxin type strains within a physiological group; there was less cross-reaction between physiological groups and very little reactivity of C. botulinum reagents with nontoxigenic organisms. Absorption of cross-reacting antibodies was not successful. Certain agents could be used for presumptive laboratory idenification of C. botulinum strains causing botulism, especially in infants. The type G reagent provided a good means of identifying C. botulinum type G, which lacks the lipase marker and the toxigenicity of which may be more difficult to demonstrate in mixed cultures. There was a serological relationship between C. botulinum type G and some strains of C. subterminale. This relationship provided evidence of differences between strains of C. botulinum type G isolated in 2 different countries.