Extracellular proteins in five clostridial species from human infections

347 strains from human infections were identified by gas-liquid chromatography of metabolic products and by conventional tests. Simple agar-plate assays were used to analyze the ability to form extracellular proteins. More than 90% of all strains were hemolytic on agar containing rabbit erythrocytes and all were gelatinase producers. All strains of C. bifermantans, C. sordelli, and C. sporogenes were also caseinolytic on skimmed-milk agar, but strains of C. perfringens, C. novyi types A and B were not. Less than 10% of C. perfringens strains were producers of elastase and staphylolytic enzyme and all other species were non-producers. All C. perfringens, C. novyii, C. bifermentans, and C. sordelli were lecithinase producers, but C. sporogenes was not. All strains of C. sporogenes formed deoxyribonuclease, while a varying number of the other species showed a positive reaction.