Microbial contamination of hematopoietic stem cell products: incidence and clinical sequelae

Microbial contamination of hematopoietic stem cell products is a rare but potentially fatal complication of hematopoietic stem cell transplantation. We report the incidence of contaminated products and describe the clinical outcomes for 35 patients at the University of Minnesota who received contaminated products from January 1990 to December 2004. In total, 2935 products were infused for 2863 transplants during this time, 36 of which 36 (1.2%) were contaminated. Coagulase negative Staphylococcus was the predominant species isolated on culture of the hematopoietic stem cell products. Patients received prophylactic antibiotics before infusion of the contaminated product based on the organism identified from culture and antibiotic sensitivities, if known. After transplantation, blood cultures from 2 patients grew the same pathogen as in the infused contaminated product, including 1 patient who had blood cultures positive for Pseudomonas cepacia. All patients who received contaminated products had benign post-transplantation courses except for the patient with Pseudomonas bacteremia, who ultimately died from complications. These results suggest that, although rare, microbial contamination of stem cell products does occur and there must be ongoing efforts by physicians and laboratory personnel to minimize the risk for introduction of contaminants. Prophylactic antibiotics are useful for certain contaminants; however, caution must be exercised when gram-negative contaminated products are administered.