Risk factors for microbial contamination of a peripheral stem cell product:
(1) large volume leukopheresis (> 15 liters processed)
(2) multiple samples taken for microbial culture
where:
• The significance of the multiple samples could reflect either (a) more handling and entry into the product thereby increasing the risk of contamination or (b) increasing the amount of fluid cultured which might detect lower numbers of organisms.
• Large volume procedures take longer but may simplify processing.
• The most common cause of a positive culture post-processing was a coagulase-negative Staphylococcus species.
A positive culture from a sample taken after specimen processing was a risk factor for a positive culture after thawing of a cryopreserved specimen and after infusion.
The bacterial isolate friom a stem cell product culture:
(1) may or may not be the same organism cultured from a patient after the product is transfused.
(2) may not be associated with infection in the recipient (of 20 contaminated products transfused, 9 patients did not have infection after the stem cell transplant. This occurred most often when coagulase-negative Staphyloccus was isolated.)
It is important to treat a febrile patient with a broad spectrum antibiotic regimen guided by blood culture and not to rely on the stem cell product culture result.
When collecting a peripheral blood stem cell product:
(1) Skin preparation prior to venipuncture should be scrupulous. Infection of central vein catheters dropped significantly when barriers and surgical gowning are used.
(2) Potential sources of contamination during processing should be identified and controlled.
(3) Entry into the product after the collection should be minimized.
