Staphylococcus aureus bloodstream infection due to contaminated hematopoietic stem-cell graft

To the Editor—The Foundation for the Accreditation of Cellular Therapy and the American Association of Blood Banks publish guidelines to ensure the quality and safety of hematopoietic stem-cell (HSC) products. These HSC products are generally cultured after procurement by the collection facility and following processing at the transplant center. Reported contamination rates of HSC grafts range from 1% to 45%. The clinical significance of infusion of contaminated HSC products is unclear. When fresh products are used, contamination is often not identified prior to HSC infusion. Bacterial contamination is not an absolute contraindication to HSC infusion, as options are limited following a myeloablative preparative regimen. In a review of 12 studies, 91% of contaminated grafts contained bacterial species of low pathogenicity (eg, Staphylococcus epidermidis and Propionibacterium acnes). Of 26 patients who received grafts contaminated with highly pathogenic bacteria (eg, S. aureus), none developed symptoms or had a positive culture matching an organism found in the HSC graft. In prior reports of infections putatively caused by graft contamination, confirmation that the graft was the source of infection was based solely on the finding of identical species. Contrary to these prior reports, we present a case of catheter-related bloodstream infection with methicillin-susceptible S. aureus due to a contaminated HSC graft in which pulsed-field gel electrophoresis (PFGE) confirmed that the graft and patient isolates were identical