Preliminary results for a new final package test to assess the quality of sterile package systems

To develop a microbial test method to ascertain the passage of airborne bacteria through the medical device packaging system after sterilization, and to apply this test method to flexible packages under mechanical pressure changes.

Petri dishes filled with nutrient agar were integrated into the packaging unit prior to sterilization. We examined paper packaging consisting of 1 (single-paper packaging [P]), 2 (double-paper packaging [PP] and textile and paper double packaging [TP]), and 3 (double packaging with transport packaging [TPP]) layers. After sterilization, the test packages were pressed five times per minute for 1 or 3 hours by a mechanical device weighing 1 kg. This exposure took place in rooms with an average airborne bacterial count of 35 (room 1) or 440 (room 2) CFU/m3. The packaging was opened following culture at 37 degrees C for 48 hours to determine the number of colonies formed.

The proportion of contaminated packages rose with the duration of mechanical stress and increased airborne bacteria concentration. Thus, mechanical pressure change for 3 hours resulted in the contamination of 60% (P), 15% (PP), 0% (TP), and 0% (TPP) of the packages in room 1, whereas 100% (P), 65% (PP), 73% (TP), and 0% (TPP) of the packages in room 2 were contaminated.

This test method allows sterile packaging systems to be tested for contamination under practical conditions without extensive laboratory preparation. Contamination as a result of laboratory errors can be ruled out almost certainly.