Background: Positive microbial cultures of peripheral blood progenitor cell (PBPC) products, although estimated to be low, are serious events in the manufacture of hematopoietic progenitor cell (HPC) products that warrant a thorough investigation to determine the contamination source.
Study design and methods: Two patients underwent autologous PBPC collection. The first patient was admitted before the collection and was febrile intermittently throughout hospitalization. The second patient spiked a low-grade fever by the end of the procedure. The HPC products from each patient were cultured during processing and before infusion. Blood cultures were drawn during febrile episodes and before transplant. Bacterial identification and antimicrobial susceptibilities were performed on all positive cultures. All strains were typed using pulsed-field gel electrophoresis (PFGE) to determine their relatedness.
Results: The blood cultures from both patients and their corresponding HPC products grew Staphylococcus epidermidis. The PFGE pattern of the S. epidermidis recovered from each patient blood was indistinguishable from the one recovered from the corresponding HPC product. The gel pattern of the strains recovered from the first patient differed by four bands from the one recovered from the second. For each patient, the antibiotic susceptibility patterns of the blood cultures and the HPC products were identical. Infusion of the contaminated HPC had no adverse event, and the patients engrafted successfully.
Conclusion: By use of PFGE technology, the contamination source of PBPC products was identified. It is concluded that the contamination resulted from intermittent bacteremia in the donors and was not introduced during laboratory manufacturing.