International reference preparation of anti-staphylococcal P-V leucocidin serum.

The National Institute for Medical Research, London, England, was requested by the WHO Expert Committee on Biological Standardization to arrange a collaborative assay of a serum they had obtained which was suitable to serve as an international reference preparation of anti-staphylococcal P-V leucocidin serum. Seven laboratories in 5 countries assayed a batch of this serum against 4 test preparations. On the basis of the results obtained, the serum has been established as the International Reference Preparation of Anti-Staphylococcal P-V Leucocidin Serum and the International Unit of Anti-Staphylococcal P-V Leucocidin Serum has been defined as the activity contained in 0.3565 mg of the International Standard.