Sterility Maintenance of Isolators After a Power Failure

Background
The Cytotoxic Production Unit (CDP) is equipped with N1000 and N4N2 isolators (JCE Biotechnology^®). The airlocks seals on the doors are rigid for the N1000 and inflatable for the N4N2, ensuring the system integrity. Power supply incidents (ou failures) occurred, causing the isolators to shut down and potentially compromising sterility. Production could only restarted after a time-consuming full sterilisation process, resulting in delays in treatment administration.

Objective
Determine how long the isolators remain sterile after apower outage (or failures, loss of power supply).

Materials and methods
The sterility of the preparations and the environment following a power interruption was performed on the isolators using aseptic process simulation filling tests, the Media Fill Test (MFT), and by environmental sampling with/using contact Tryptic Soy Agar (TSA) plates and a microbial air sampler. Power outages were simulated for 15 mins, 30 mins, 4 hours, 12 hours and 24 hours for the N4N2, and for 24 hours, 48 hours and 72 hours for the N1000 (previous tests had demonstrated adequate sealing of the rigid seal for several days). On each isolator, positive controls were prepared using a strain of S.aureus (ATCC 29213) at 100 CFU/mL. Under each condition, the isolators were first sterilized, then the power supply was interrupted for the specified duration of the test. They were subsequently switched back on and the MFT tests were carried out.
Each MFT test was repeated three times and include one bag (50 mL) and four syringes (one 30 mL and three 10 mL syringes), which were incubated for 14 days at 32.5°C. In parallel, five contact agar plates and two 1 m³ air samples collected using an aerobiocollector were incubated for 3 days at 32.5°C, followed by 11 days at room temperature, exceeding the standard recommendations of the European Pharmacopoeia (Ph. Eur).

Results
For both isolators, S. aureus positive controls cultures tested showed growth withing 24 hours. All AFT tests were negative after 14 days of incubation.
For N1000, contamination by low-pathogenic environmental bacteria (particularly S. capitis) was detected on contact agar plates from the 24 hours and 72 hours outage tests. As the time taken for these agar plates to turn positive exceeded the recommendations of the European Pharmacopoeia, a second series of test was conducted after 24 and 72 hours outages, and all results and all other samples were negative.
For the N4N2, the air samples collected using an microbial air sampler showed microbiological contamination on the test after a 12-hour test. The other samples were negative.

Conclusion
The results indicate that both isolator environmental sterility and sterile production can be maintained for a limited period following a power failure. The sterility hold timed retained were 4 hours for the N4N2 isolator and 48 hours for the N1000 isolator. Additionnal tests are planned for the N4N2 to further investigate power outage durations between 4 to 12 hours.

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