Size characterization of Mycobacterium bovis BCG (Bacillus Calmette Guérin) vaccine, Tice substrain.

Reconstituted, lyophilized, attenuated Mycobacterium bovis, Bacillus Calmette Guérin (BCG) vaccine, Tice substrain, was characterized using a Coulter Multisizer and a HIAC/Royco counter. The primary organism has an equivalent spherical diameter approximating 1 micron but the BCG cell suspension is heavily aggregated. The cumulative size distribution of the suspension fits a log-probit plot and this information can be used to determine the total number of particles per ampoule. The instrumental count may be related to the viable count. The state of dispersion was unaffected by mild shear (syringe aspiration or ultrasound) and only slightly affected by the addition of cetylpyridinium chloride or sodium tauroglycolate.