The testing and standardization of B. welchii (perfringens) antitoxin / T. Dalling [and others].

Date:
[1928?]
Catalogue details

Licence: In copyright

Credit: The testing and standardization of B. welchii (perfringens) antitoxin / T. Dalling [and others]. Source: Wellcome Collection.

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    doses if this amount were contained in a convenient volume of the toxin, as in the case of diphtheria, tetanus, botulinus and oe,dematiens toxins. The volume of 100 m.l.d. of B. welchii toxin would be inconveniently large; it is, however, possible to make use of 10 m.l.d. in the pigeon-intramuscular method and the mouse-intravenous method. A toxin having been chosen whose test-dose is contained in a convenient volume and representing a reasonable number of lethal doses, it is next necessary to find its equivalent in standard serum; this now becomes the standard to which all future references are made. Whether this equivalent is termed one unit or some fraction of a unit is a matter for later consideration. Bengtson determined the amount of a certain serum protecting against ten pigeon-intramuscular fatal doses of a certain toxin and called it l/100th of a unit. The standard serum chosen by her contained 100 equivalents, and therefore 1 unit per c.c. The method chosen by us was as follows: A “ toxin ” was prepared, precipitated by ammonium sulphate, dried and ground; this material is reasonably stable, whereas the liquid toxin may rapidly deteriorate. A typical titration of such a toxin is shown in Table IV. Approximately ten times the mouse-intravenous fatal dose was accepted as a convenient “ test dose ” of toxin. A certain serum of low value was chosen as our standard serum. The volume of this serum which, when mixed with the test dose of toxin and injected into mice, protected half of a group of six or more mice, was determined in a series of tests ; it proved to be 0'00‘22 c.c. A dose of serum about 10% higher, 0’0025 c.c., usually protected 90% or more of the mice, whereas a dose 10% lower, 00020 c.c., usually failed to protect 90% or more of the mice. Table IY.—Titration of Toxin. c.c. of toxin. 16 in gun. per c.c. 0-03 0T25 0-02 0*015 o-oi Precipitated : Mice, intravenously. + + + + L + + L L L L L L A second test toxin was titrated against the standard serum until a test dose was chosen which gave corresponding results with these doses of the test serum. This test dose of toxin was found to contain nearly 20 fatal doses. Thus it is seen that, as in the case of diphtheria and tetanus and other toxins, the number of fatal doses contained in the ‘‘test dose” of toxin is not constant, but depends on the relation between the amount of toxin and toxoid present. Possibly the English Authority under the Therapeutic Substances Act, the U.S.A. Public Health Service and the League of Nations Standardization Committee will eventually decide on an official unit. Meanwhile we felt that
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