Cross-contamination risk and decontamination during changeover after cell-product processing

Introduction: During changeover in cell-product processing, it is essential to minimize cross-contamination risks. These risks differ depending on the patient from whom the cells were derived. Human error during manual cell-product processing increases the contamination risk in biosafety cabinets. Here, we evaluate the risk of cross-contamination during manual cell-processing to develop an evidence-based changeover method for biosafety cabinets. Methods: Contaminant coverage was analyzed during simulated medium preparation, cell seeding, and waste liquid decanting by seven operators, classified by skill. Environmental bacteria were surveyed at four participating facilities. Finally, we assessed the effect of conventional UV irradiation in biosafety cabinets on bacteria and fungi that pose a cross-contamination risk. Results: Under simulated conditions, scattered contamination occurred via droplets falling onto the surface from heights of 30 cm, and from bubbles rupturing at this height. Visible traces of contaminants were distributed up to 50 cm from the point of droplet impact, or from the location of the pipette tip when the bubble ruptured. In several facilities, we detected Bacillus subtilis, of which the associated endospores are highly resistant to disinfection. Irradiation at 50 mJ/cm2 effectively eliminated Bacillus subtilis vegetative cells and Aspergillus brasiliensis, which is highly resistant to UV. Bacillus subtilis endospores were eliminated at 100 mJ/cm2. Conclusions: Under these simulated optimal conditions, UV irradiation successfully prevents cross-contamination. Therefore, following cell-product processing, monitoring the UV dose in the biosafety cabinet during cell changeover represents a promising method for reducing cross-contamination.