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Bacterial contamination of peripheral blood progenitor cells for transplantation
H K Jestice1, M Farrington, C Hunt
1Department of Clinical Haematology, Addenbrooke's NHS Trust, Cambridge, U.K.
Abstract:
Peripheral blood progenitor cells (PBPC) were obtained from 128 apheresis harvests on 64 patients and were tested in duplicate for microbiological contamination (1) after collection and (2) after thawing, following processing and cryopreservation. In this study we have attempted to improve the monitoring of contamination in peripheral blood progenitor cell collections by identifying exogenous contamination that probably originated from the testing laboratory and is therefore not clinically significant. We found no contamination in 82% of harvests, 1.6% of harvests to be significantly contaminated and organisms were isolated from 16.4% that were assessed as clinically nonsignificant. Our experience indicates that the choice of microbiological methods will influence the results and their clinical relevance. No samples were positive by direct culture. We recommend that sampling should be performed at more than one stage during the procedure and that initially only the post-thaw samples be analysed. Testing should be performed by enrichment culture in duplicate only and if positive to aid interpretation the post-collection sample should then be cultured. No patient given nonsignificantly contaminated graft without antibiotic cover suffered infection from the identified organism. The incidence of significant contamination was low and we recommend that in these cases PBPC grafts can be infused safely provided prophylactic antibiotic cover is given.
Insights
This study on peripheral blood progenitor cell (PBPC) collections found most contamination was not clinically significant. Safe infusion of PBPC grafts is possible even with some contamination, with appropriate antibiotic cover.
Area of Science:
- Hematology
- Microbiology
- Transplantation Science
Background:
- Microbiological contamination of peripheral blood progenitor cell (PBPC) collections poses a risk to patients undergoing transplantation.
- Accurate monitoring is crucial to differentiate clinically significant contamination from laboratory-derived or non-pathogenic organisms.
Purpose of the Study:
- To improve the monitoring of microbiological contamination in PBPC collections.
- To identify exogenous contamination and assess its clinical significance.
- To optimize testing protocols for PBPC apheresis harvests.
Main Methods:
- Testing of 128 PBPC apheresis harvests from 64 patients for microbiological contamination.
- Duplicate testing performed post-collection and post-thaw after processing and cryopreservation.
- Utilized enrichment culture methods, with direct culture as a comparison.
Main Results:
- 82% of harvests showed no contamination.
- 1.6% of harvests had significant contamination.
- 16.4% of harvests yielded organisms deemed clinically non-significant.
- No samples were positive by direct culture.
- No infections occurred in patients receiving non-significantly contaminated grafts without antibiotic cover.
Conclusions:
- The choice of microbiological methods significantly influences contamination detection and clinical relevance.
- Recommends multi-stage sampling (post-collection and post-thaw) with initial analysis of post-thaw samples.
- Suggests enrichment culture in duplicate, with post-collection culture if initial results are positive.
- Low incidence of significant contamination allows safe PBPC graft infusion with prophylactic antibiotics.