What is the clinical significance of infusing hematopoietic cell grafts contaminated with bacteria?

Although hematopoietic stem cell (HSC) products are routinely cultured for sterility, bacterial contamination of these products is rarely observed and little is known about the clinical consequences of infusing contaminated grafts. We retrieved the sterility cultures of bone marrow and peripheral HSC grafts from 938 patients transplanted at our center from January 1990 to July 2005. Fever, septicemia and other adverse events were assessed for up to 14 days following infusion of the graft. Out of the 1502 grafts collected during this 15-year period, 15 (1.0%) had a positive sterility culture (11 Gram-positive cocci, 2 Gram-positive bacilli and 2 Gram-negative bacilli). No correlation was observed between the graft contamination rate and the extent of graft manipulation or the patient's underlying condition. Thirteen recipients were transplanted with contaminated grafts. Five patients were treated with specific pre-emptive antibiotics. Only one episode of Staphylococcus epidermidis bacteremia possibly related to a contaminated graft was observed on day +5. As the infusion of contaminated grafts with Gram-positive skin contaminants rarely results in unfavorable clinical outcomes, close patient monitoring without the use of specific pre-emptive antibiotics could be appropriate and could avoid antibiotic-associated adverse events.