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Background

Microbial contamination of hematopoietic progenitor cells (HPCs) and other regenerative cells used in transplantation and regenerative medicine can occur during collection and after in vitro manipulation, including purging, cryopreservation, thawing, and infusion.

Study Design And Methods

Microbiologic culture findings on consecutive HPCs and other cell preparations at a single institution derived from peripheral blood, marrow, cord blood, and mesenchymal stromal cells during all phases of manipulation were retrospectively examined from 2005 through 2011. Results were classified as confirmed positive, false positive, and indeterminate.

Results

During the 6-year surveillance period, 365 patients underwent 912 procedures involving HPC or other cell-based transfusion. True positive microbial contamination was found in five of 663 (0.8%) peripheral blood and two of 34 (5.9%) marrow preparations (p = 0.04), while no contamination was found in 118 preparations from other sources. True-positive microbial contaminants included coagulase-negative staphylococci in autologous HPC products derived from peripheral blood from two patients with asymptomatic central venous catheter infections at time of apheresis and Propionibacterium acnes in one apheresis and two marrow products. Organism loads were low in all cases (≤500 colony-forming units/mL), and no adverse sequelae occurred in four patients that received contaminated products.

Conclusion

The incidence of microbial contamination of progenitor cell products in our institution over a 6-year period was low (0.8% overall), with contaminants originating from infected central venous catheters or from skin flora. All contaminants were bacterial species of low virulence, present in low titers and, if transfused, did not result in adverse reactions.