PREPARATION AND ASSAY OF THE INTERNATIONAL STANDARDS FOR CLOSTRIDIUM BOTULINUM TYPES A, B, C, D AND E ANTITOXINS.

The National Institute for Medical Research, London, was authorized in 1962 by the WHO Expert Committee on Biological Standardization to establish the International Standards for Clostridium botulinum Types A, B, C, D and E Antitoxins and to define the International Units. For this purpose use was made of the material accepted in 1954 as the British reference preparations and reconstituted in 1960 for establishment as the first British standards.The author describes the methods of preparation of this material and results of examinations, including estimates of the quality of the antitoxins (assessed as an "efficiency ratio") and of the specificity of the sera.The International Unit is defined as the specific activity contained in a known weight of dried antitoxin of each Cl. botulinum type: for Type A, 0.1360 mg; for Type B, 0.1740 mg; for Type C, 0.0800 mg; for Type D, 0.0121 mg; and for Type E, 0.0691 mg.