Development of molecular sterility assay for rapid quality release of cord blood erythrocytes units for transfusion.

Background: Umbilical cord blood (CB) units stored in banks are an important source of hematopoietic stem cells for transplantation and other cell therapies. New applications, such as their use in transfusions, require rapid quality release as cord blood red blood cells (CB-RBC) have a shorter shelf life.

Study design and methods: This project aims to investigate the most prevalent microbial contaminants in CB preparations and validate a rapid sterility testing strategy for CB-RBC based on an automated system (BACT/ALERT®) in tandem with a molecular assay (real-time PCR) capable of detecting at least 100 CFU/mL of Cutibacterium acnes in CB-RBC to accelerate the detection of the most common slow-growing bacteria.

Results: Microbial contamination incidence was assessed by reviewing 4696 CB sterility tests, revealing a positivity rate of 3.4%, with C. acnes being the most common slow-growing pathogen. The BACT/ALERT® system, which was validated according to European Pharmacopeia guidelines, was an appropriate method for sterility testing of CB-RBC, although it required up to 14 days of culture to detect C. acnes when iFAPlus and iFNPlus bottles were used to neutralize antimicrobials. Interestingly, the BACT/ALERT® method detected C. acnes at 30 CFU/mL within 14 days, while real-time PCR identified concentrations ≥65 CFU/mL by Day 4.

Discussion: In conclusion, we developed a rapid sterility testing strategy that combines automated culture systems and real-time PCR for early microbial contamination, enhancing CB-RBC shelf life for transfusion and emphasizing the importance of combining detection methods.