Collaborative studies for the establishment of reference substances for the microbiological assay of antibiotics.

Collaborative studies were initiated by the European Directorate for the Quality of Medicines (EDQM) to assign potency values for candidate European Pharmacopoeia Chemical Reference Substances (Ph. Eur. CRSs) used for the microbiological assay of antibiotics. The candidates were assayed against their respective International Standard (IS), using the methods by diffusion or turbidimetry. Potencies were assigned to all the antibiotics concerned, which were adopted by the European Pharmacopoeia Commission.