Interlaboratory study comparing the microbiological potency of spiramycinsI, II and III

An interlaboratory study has been performed to determine the relative poten cies of spiramycins (SPMs) I, II and III by diffusion or/and turbidimetric assays with Bacillus subtilis or Staphylococcus aureus as the test organism s. Six laboratories from three countries participated. Experimental procedu res were according to the European Pharmacopoeia, 3rd ed. The activity of S PM I is markedly higher than that of SPM II and LII. By diffusion, the acti vities of SPM II and III relative to SPM I were found to be 57 and 72%, res pectively. The interlaboratory relative standard deviations (RSD) varied fr om 3.6 to 16.3%. By turbidimetry, the activities of SPM II and III relative to SPM I were found to be 45 and 52%, respectively. The interlaboratory RS D values varied from 2.6 to 7.7%. The results of the study were analyzed ac cording to the ISO 5725-2 guidelines to determine the repeatability, the be tween-laboratory and the reproducibility variances of both methods. (C) 199 9 Elsevier Science B.V. All rights reserved.