Quantitative microbiological assay of thiomersal using agar diffusion from paper discs

A quantitative assay method for determination of thiomersal in biological products is described and evaluated. A microbiological method using agar diffusion from filter paper discs is used. The advantages of the method in terms of low cost and reliability for determining the actual antimicrobial activity in the preparation are discussed. The assay method is in routine use in the production control of vaccines at our Institute.