Microbial contamination of isolators: from risk analysis to decision-making flowchart

Aims
How to deal with microbiological non-compliance of production equipment is a difficulty for the teams and regularly leads to delays and heterogeneous decisions. A Preliminary Hazard Analysis (PHA) was carried out in our chemotherapy preparation unit to determine possible areas for improvement.

Method
The multidisciplinary working group met 8 times from March to October 2020, in order to identify, analyze, prioritize and assess the risks associated with this process. Two scales (severity degree of hazard and possibility of occurrence of hazard) were defined to evaluate initial and residual criticality after the implementation of the corrective actions.

Results
The studied process was divided into 3 phases. The analysis identified 6 hazards, of which 3 were the main ones: in decreasing order of frequency, the organisational factor, the physico-chemical factor and the financial factor. Fifteen priority situations were identified with 18 scenarios developed: 14/15 (93%) have a tolerable initial risk under control (level 2) and 1/15 an unacceptable initial risk (level 3). After proposing 7 corrective measures, the scenarios become either acceptable as they are (93%, 14/15) or tolerable under control (7%, 1/15). The phase with most of the dangerous situations is the sampling conditions. The main corrective measure resulted in the creation of a decision-making flowchart on what to do in the event of a positive microbiological sample from an isolator. Several parameters were taken into account: type of sampling (sterile glove, aerobiocontamination control, microbiological surface control), the sterilisation date of the isolator concerned and the availability of an alternative means of production. The implementation of other actions allowed a rapid improvement of our practices, as they were easily achievable (simplification of sampling procedures, acquisition of a second oven, updating of the checklist of actions in the ZAC, creation of a summary table of the type of agar used and sampling frequencies).

Discussion/conclusion
This PHA made it possible to review the possible situations and to propose a decision logigram describing the action to be taken in the event of a non-compliant microbiological result, allowing for faster and more consistent decision-making. A re-evaluation of the effectiveness of this new procedure is planned one year after its implementation.

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