Bacterial contamination of autologous bone marrow during processing

We were interested to read the report by Smith et al. bacteriological monitoring of 14 bone marrow harvests. They found a 36% bacterial contamination rate before cryopreservation, which rose to 45% at the thawing stage. We also monitor bone marrow harvests, and 34 (39.5%) of the 86 harvests cultured between January 1995 and April 1996 were positive with a comparable (although broader) range of isolates to those reported by Smith et al. To the microbiologist's eye, there are many similarities between the processes of bone marrow and peripheral blood stem cell (PBSC) harvest, and our recently published experience of monitoring 128 PBSC harvests from 64 patients has interesting analogies and contrasts with the results from University College. We cultured at the same stages as Smith et al., but in duplicate, and found 18.0% PBSC harvests to be contaminated, two (1.6%) of these with the same bacteria in both duplicate post-cryopreservation cultures.