Relation of in vitro inhibition by chelates of Clostridium perfringens alpha-toxin to their ability to protect against experimental toxemia.

The inhibition of Clostridium perfringens alpha-toxin by ethylenediaminetetraacetate (EDTA) and diethylenetriaminepentacetate (DTPA) was studied utilizing three different in vitro assay procedures: diffusion on egg yolk-agar, disintegration of muscle sections, and manometric assay with partially purified lecithin as substrate. DTPA was 10 to 20 times more efficient as an inhibitor than EDTA in systems containing relatively large amounts of calcium; these observations were similar to those observed in previous in vivo protection studies. A number of other chelating agents were tested for their ability to inhibit alpha-toxin in vitro and protect mice against it; the chelating agents which were the most efficient in vitro inhibitors had the greatest in vivo protective ability.