Single-Use System Integrity I: Using a Microbial Ingress Test Method to Determine the Maximum Allowable Leakage Limit...

Area of Science:

• Biopharmaceutical Manufacturing
• Microbial Integrity Testing
• Risk Assessment

Background:

• Single-use systems (SUSs) are increasingly used in biopharmaceutical manufacturing, making their integrity critical for drug safety and cost-effectiveness.
• Assessing microbial ingress and leakage in SUSs requires robust scientific methods to ensure product quality and patient safety.
• Existing integrity testing methods need enhancement to reliably predict potential microbial contamination risks.

Purpose of the Study:

• To design and validate an aerosol microbial ingress test for determining the Maximum Allowable Leakage Limit (MALL) of single-use systems (SUSs).
• To develop a predictive model for MALL based on experimental data, considering various physical and microbial factors.
• To establish a scientifically sound method for assessing the microbial integrity of SUSs under simulated real-world conditions.

Main Methods:

• Developed an aerosol microbial ingress test using film patches (ethylene vinyl acetate and polyethylene) with laser-drilled defects (1-100 µm).
• Exposed test units filled with culture media to a standardized aerosol of *Bacillus atrophaeus* spores under varying pressures (0-300 mbar).
• Utilized logistic regression analysis to statistically determine the MALL based on observed microbial ingress over a 14-day incubation period.

Main Results:

• The microbial integrity test successfully detected bacterial ingress through defects as small as 3 µm.
• Estimated MALL values were determined for typical use-case conditions: 10-20 µm for storage and 2-10 µm for shipping.
• The study demonstrated a probabilistic approach to MALL determination, integrating defect size, material properties, and microbial challenge.

Conclusions:

• The developed aerosol microbial ingress test provides a reliable and accurate method for predicting the MALL of single-use systems.
• This method enhances the scientific basis for single-use system integrity (SUSI) assessment, improving drug safety and manufacturing assurance.
• The findings support more accurate risk assessments and informed decisions regarding the use and integrity validation of SUSs in biopharmaceutical processes.