Mystery of Bio-burden over moist heat terminal sterilization process journey

Monitoring of bioburden is one of the most important aspect of terminal sterilization. Before sterilization all samples to be collected based on the predetermined interval to cover the complete process/manufacturing time. Sample to be collected in the final container to represent to bioburden in the unsterile product bioburden at beginning, middle and end of the process to represent the worst-case scenario.

Although the regulatory requirements are quite relaxant for terminal sterilization as the product get sterilized in the final container, however proper CIP/SIP of compounding vessel, use pre-sterilized items for manufacturing and filling activity, better aseptic practices, maintaining adequate environment for filling and sealing will helpful to control the bioburden level.

 Heat resistance test is helpful to understand the resistivity of the heat-resistance bacteria (spore-forming) on the unsterile product before sterilization. Tn the test collected samples are treated with heat at water bath at 80-100°C for 10 to 15 minutes and pass through a membrane filter under certain condition. Bacterial species detected from microbial limit test to be considered for identification. Data obtained from the identification to be used for sterilization resistance test and to understand route of contamination to build up better control.

Bacterial spore to be germinated into a suitable growth medium. D value should be determined at a product sterilization temperature according to procedures specified in ISO 11138.

If D-value determination is difficult, the reason for the difficulty should be clarified, and a suspension of viable cells at a count of more than 106/product should be prepared, heated for half of the sterilization time required to inactivate all of 106 counts of microorganisms (on the soybean-casein digest agar medium), and verified to be negative (to achieve 12-log reduction [12D] over the predetermined sterilization time) by the Sterility Test, “Membrane Filtration,” to ensure a SAL of 10-6.

Heat labile products always process through overkill approach which can with stand 121°C temperature for more than 15 min or F0 ≥12. It was a less complicated process with high control and better sterility assurance. Even minimum documentary evidence needs to be submitted to regulatory agencies compare to product specific method. Whereas Biological indicator/bioburden combined process and Bioburden-based process are the subsequent choice. Its all depends on the product behavior observed during development and design stage. 

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3. Growth in BI at Moist Heat Terminal Sterilization