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The Potency of Staphylococcal Toxoid

From the Connaught Laboratories, University of Toronto

Abstract

1. Samples of staphylococcal toxoid as distributed for human use were tested in vitro for combining value with antitoxin. They ranged in potency from 1.2 to 51 L_b/ml.

2. Three selected samples with dilutions thereof, having a representative range of in vitro potency, were injected into 6 groups of 8 or more rabbits according to the method proposed by the National Institute of Health. The specimens of blood from individual rabbits were titrated for antitoxin separately and the results subjected to statistical analysis. The arithmetic mean antitoxic titer of the various groups showed that only the toxoid which had a combining value of 2.3 L_b/ml failed to pass the test. The analysis of the figures shows, however, that two toxoids which contained 3 L_b/ml would have only a small chance of passing retest. These should therefore be considered borderline toxoids. Toxoids which contained more than 10 L_b/ml passed the test with ease and the statistical analysis showed that they would probably never fail to do so.

3. The requirements of the test proposed by the National Institute of Health are discussed in the light of these results and suggestions made for alterations in these requirements.

4. It is proposed that the combining value with antitoxin be included as a complementary criterion of the antigenic potency of staphylococcal toxoid.