Comparison of two methods for microbiological control of isolator for reconstitution unit of cytotoxic drugs

Objectives

Evaluate the reliability of microbiological samples taken by agar impression, compared to a dry swab at the same sampling points. Evaluate the relevance of swab for hard-to-access areas.

Methods

Controls conducted over 4 weeks by agar impression (count-tact agar) and by dry swab after the last preparation session and before bio cleaning. They cover the interior, isolator air-locks and the external environment (benches). A weekly cadence setting defines the sampling points. Contact plates were incubated at 30 ° C. TSB-T culture broths are inoculated with the swabs and then transplanted onto COS agar. After 72 h of incubation, results are interpreted according to the Good Preparation Practices (GPP) guidelines.

Results

Week 1: positive growth on the agar sample from the external closed-system preparation bench (3 CFU / 25cm²).
Weeks 2 and 3: all results are negative.
Week 4: two positive samples on agar from the preparation bench in closed-system (9 CFU / 25cm²).

Morphological identification isolated bacteria of the genus Staphylococcus and Micrococcus sp. The same week, an air-lock swab of the isolator was positive with gram positive cocci (probably Staphylococcus sp). A remote sampling (1 week) from the same point was negative suspecting transient contamination.

Conclusion

The results of both methods are below thresholds and / or with non-pathogenic germs. The isolator is "GPP compliant". The two methods are complementary. The agar print, easily standardized, allows a qualitative and quantitative analysis. It will be kept as a reference method. Swabbing allows the analysis of hard-to-access areas, but only allows qualitative control after enrichment. Its installation for the routine sampling of hard-to-access areas of the isolator is conceivable.