Prevalence of Microbially Contaminated Hematopoietic Stem Cell Products.

In 2001, the Docket Report from the Food and Drug Administration expressed concerns regarding the potential of microbially contaminated hematopoietic stem cell products to produce morbidity and mortality in transplant recipients. This concern was the basis for development of regulatory standards for hematopoietic stem cell products.

We surveyed a total of 2972 patients at 121 U.S. transplant centers that registered patients with the CIBMTR in the years 2000 and 2001. Information regarding microbial contamination of infused grafts was obtained from 94 transplant centers (80% response rate) for 2312 patients. 52 (2%) of 2286 infused grafts tested were culture positive for bacterial or fungal organisms. The microbial isolates included: coagulase negative staphylococcus (56%), gram negative organisms (15%), coagulase positive staphylococcus (10%), gram positive rods (10%), streptococcus (8%), and fungus (1%). Prophylactic antibiotics targeted at the contaminant were given to 17 of the 52 recipients of contaminated grafts. Antibiotic regimens included vancomycin alone (76%), aminoglycosides and vancomycin (12%), or cephalosporin and vancomycin (12%). 47 (50%) of the centers that participated have existing policies regarding contaminated products. Patients with non-malignant disorders or who received bone marrow were more likely to have a contaminated graft. No differences in age distribution, sex, race, type of transplant (allogeneic vs autologous) and year of transplant were noted between recipients of contaminated and non-contaminated grafts. The unadjusted 100-day survival of persons receiving contaminated grafts was 86% (95% Confidence Interval [CI] 72–93%) versus 81% (95% CI 80–83%) among those receiving non-contaminated grafts, p=0.35.

In summary, about 2% of hematopoietic stem cell products infused for allogeneic or autologous transplantations in U.S. centers will test positive for microbial contamination, but such contamination does not increase posttransplant mortality. The absence of significant 100-day mortality among patients infused with contaminated grafts suggests that stringent regulatory policies regarding the use of contaminated hematopoietic cell products may not be indicated.