ON THE MECHANISM OF KILL OF MICROBIAL CONTAMINANTS DURING TABLET COMPRESSION

Separate batches of three tabletting excipients, lactose monohydrate, maize starch and Avicel PH-101, were contaminated with vegetative bacteria, Staphylococcus aureus or Enterobacter cloacae. The bacteria were allowed to grow in the excipient, such that they were adhered to the surface of the powder. The contaminated powders were tabletted at various compression forces. The extent of kill was assessed for each organism and compression/kill curves were produced. The extent of kill on tablet compression was greatest for the larger organism, E. cloacae, indicating that size is important and that cell rupture by shear, rather than heat, is the mechanism of kill. The type of consolidation during compaction (plastic flow or brittle fracture) influenced survival, plastic flow causing the greatest kill at low compression forces. The results are related to published data for the kill of spores during compaction.