Biology of Blood and Marrow Transplantation 12:1142-1149 (2006) 䊚 2006 American Society for Blood and Marrow Transplantation 1083-8791/06/1211-0001$32.00/0 doi:10.1016/j.bbmt.2006.06.011
Microbial Contamination of Hematopoietic Stem Cell Products: Incidence and Clinical Sequelae Mark A. Klein,1 Diane Kadidlo,3 Jeffrey McCullough,2 David H. McKenna,2 Linda J. Burns1 1
Division of Hematology, Oncology and Transplantation, Department of Medicine, and 2Division of Transfusion Medicine, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, Minnesota; 3 Clinical Cell Therapy Laboratory, University of Minnesota, St Paul, Minnesota Correspondence and reprints requests: Linda J Burns, MD, Mayo Mail Code 286, 420 Delaware Street SE, Minneapolis, MN 55455 (e-mail:
[email protected]). Received January 16, 2006; accepted June 24, 2006
ABSTRACT 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. © 2006 American Society for Blood and Marrow Transplantation
KEY WORDS Hematopoietic stem cell transplantation
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INTRODUCTION Intravenous infusion of microbially contaminated hematopoietic stem cell (HSC) products is a potential source of morbidity and mortality in immunocompromised transplant recipients. Possible sources of contamination include asymptomatic bacteremia of the patient or donor at time of collection, infected catheters or skin plugs from venous access, and improper execution of aseptic technique during collection or processing. Standard practice is to harvest bone marrow (BM) under sterile conditions in operating rooms, peripheral blood stem cells (PBSCs) via apheresis, and umbilical cord blood (UCB) after birth in hospital obstetric units. The potential for and mechanism of contamination differ for these various collection methods. Once cell products are collected, they are transferred to the 1142
Stem cell products
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Microbial contamination
cell-processing laboratory, where they may undergo further manipulation ranging from minimal ex vivo processing to more extensive cell-engineering techniques. As cell engineering becomes more complex, the potential for introducing a contaminant through laboratory processing is increased. Contamination rates for stem cell products have been reported as 0%-45% [1-19]. Although some contaminated products described in published reports were discarded, most products were transfused by choice or necessity. In 4 reports, subsequent blood cultures yielded the same organisms as in the contaminated graft [12,15,19,20]. However, no significant adverse clinical outcomes or deaths resulted. Such a wide range of reported contamination rates suggests institutional differences in harvesting, processing, and thawing protocols and an improvement in
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collection systems and processing techniques over time. We report the University of Minnesota experience with HSC product (BM, PBSCs, and UCB) contamination, including incidence, likely etiologies, and clinical sequelae of infusion. METHODS Patients
Between January 1990 and December 2004, 2863 consecutive patients with various malignant and nonmalignant hematologic disorders underwent transplantation at the University of Minnesota. In total, 2935 HSC products were infused because some patients received 2 products (BM plus PBSC). All patients received prophylactic antimicrobials directed toward bacterial, fungal, and viral pathogens beginning 1 day before transplantation. The Cell Therapy Laboratory processing records for these patients were examined for results of sterility testing. Medical records of those patients identified as having received contaminated stem cell products were then reviewed in detail. Data gathered included whether the product was known to be contaminated, prophylactic antibiotic administration, and clinical sequelae that occurred from time of infusion to 14 days after transplantation, including side effects of infusion, results of blood cultures and antibiotic sensitivities, and development of end-organ toxicity. The study protocol was approved by the institutional review board. Sterility Testing
Before 1998 all stem cell products were sampled for bacterial and fungal cultures immediately after collection/before processing and again immediately after processing. Subsequently, due to the low incidence of contaminated products, a policy change was made to discontinue routine sampling after collection and to obtain cultures for sterility testing only at the completion of processing before cryopreservation of HSC products and before the release of fresh products (allogeneic PBSC and BM) or thawed UCB from the laboratory for infusion. Sterility testing was not typically repeated after thawing of cryopreserved products unless tears were found in the product bag or breakage occurred during thawing. Stem Cell Collection
Stem cells were collected by BM harvest, apheresis, or cord blood drainage. BM was harvested from the posterior iliac crest under general anesthesia in the operating room using sterile techniques. Through a series of aspirates, BM was collected in sterile syringes containing heparin and electrolyte solution (PlasmaLyte A [Baxter Healthcare Corporation, Deerfield, IL] or Minimum Essential Media [Invitrogen, Grand
Island, NY]). The contents of the syringe were transferred to a sterile disposable bag filtration system in which the marrow passed through a series of inline filters of decreasing size for removal of particulate matter to a final product bag. PBSCs were collected by apheresis from autologous and allogeneic donors using a Baxter Fenwal CS3000 Plus Blood Cell Separator (Baxter Healthcare Corporation, Deerfield, IL) [21]. Blood was removed from the donor through a central venous catheter port or a peripheral venipuncture site and mixed with anticoagulant solution as it entered the instrument. The total blood volume processed ranged from 15 L for adults to 3-6 blood volumes for pediatric donors. The volume of the final product was approximately 60-80 mL. UCB collections for related donations were often performed in the early years of our study by inexperienced obstetrics staff using an open system in which the cord was transected and blood allowed to drain into a sterile container containing anticoagulant (citrate phosphate dextrose, Baxter Fenwal) and antibiotics. Collections for unrelated donations were performed by various UCB banks using primarily closed systems (blood bag sets). Unrelated donations were more prominent in the later years of our study group. UCB collection volumes by either method typically ranged from 50 to 150 mL. Processing Techniques
Most (93%) products underwent minimal cell manipulation in the laboratory, which involved removal of unwanted red blood cells and plasma, volume reduction, stem cell selection, or cryopreservation before infusion. Of the 7% of products involved in extensive cell processing, techniques included counterflow centrifugal elutriation, cell expansion, gene modification, and tumor cell purging. A brief description of stem cell processing techniques used during the period of study follows. Minimal Manipulation Cell Processing ● PBSC and UCB. Collections were weighed and sampled for total nucleated cell count, cell differential, CD34⫹ cell and colony-forming unit, and viability. All manipulations were performed in a biological safety cabinet. For most allogeneic PBSC products, no further processing was necessary. Autologous PBSC and UCB cells were cryopreserved and stored in liquid nitrogen (LN2) storage tanks until the day of infusion. ● Autologous BM buffy coat preparation. Processing was performed with a COBE 2991 Cell Processor. BM was transferred to a sterile disposable tubing set (Baxter Healthcare Corporation, Deerfield, IL) connected to the device. Cells were centrifuged at 1240g until visible layers of plasma,
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red blood cells, and buffy coat (white blood cells) were created. The buffy coat layer was extracted into a sterile plastic bag and cryopreserved. ● Allogeneic BM. Laboratory manipulation included centrifugation for removal of plasma for minor ABO incompatibilities and volume reduction, red blood cell depletion by hydroxyethyl starch sedimentation technique for major ABO incompatibility, and CD34 selection with an immunomagnetic cell selection device (Isolex 300i Magnetic Cell Separation System [Baxter Healthcare Corporation, Deerfield, IL]). Extensive Manipulation Cell Processing. Techniques included T cell depletion by counterflow centrifugal elutriation, transduction of retroviral vector, and tumor purging with pharmacologic agents (interferon-␥, ricin, and 4-hydroperoxycyclophosphamide). Techniques involved multiple transfers of cells via bags, tubes, and/or syringes. Many of these processes involved extensive incubation and exposure to reagents not approved for human use and not manufactured under standards currently mandated by the Food and Drug Administration (FDA). Cryopreservation
the patient care unit in a LN2 portable shipping container, placed in sterile overwrap plastic bags, and gently thawed in a water bath containing sterile saline. Once thawed the cells were directly injected into the patient’s intravenous access or hung and administered by controlled drip. Frozen UCB products were thawed in the laboratory on the day of transplantation, washed with a 10% dextran 40/5% human serum albumin solution, and transported to the patient care unit for timely infusion. Bag Breakage Protocols
The Cell Therapy Laboratory followed established procedures in the event that a break occurred at the time of thaw. If a minor break occurred, the hole or tear was sealed with a sterile hemostat and thawing was continued. If a major break occurred, the stem cell product was collected in a syringe as it thawed and transferred into a sterile bag. Samples for culture were obtained from all bags that leaked or broke. The transfusion medicine and transplantation attending physicians were notified by the Cell Therapy Laboratory medical director, and clinical decisions regarding appropriate management, including use of broad-spectrum antibiotics, were made.
Stem cell products were cryopreserved using a cryoprotectant solution consisting of dimethylsulfoxide, electrolyte solution (Plasma-Lyte A), and 20% human serum albumin or autologous serum. Products were aseptically transferred to sterile cryogenic bags through syringes and combined with an equal volume of cryoprotectant solution. The product was placed in a controlled-rate freezer and frozen to ⫺100°C. Products were then transferred to LN2 storage containers in direct contact with LN2 (products frozen from 1990 to 1996) or in vapor phase at ⬍⫺135°C (products frozen from 1997 to 2004).
Thirty-five patients (21 men, 14 women), with a median age of 25 years (range, 7 months to 61 years), received 36 contaminated stem cell products (1 patient received a second transplant due to failure of the first HSC product to engraft; each graft was contaminated with coagulase-negative Staphylococcus [CNS]). The types of diseases necessitating transplantation included acute and chronic myelogenous leukemias, lymphoma, and BM failure syndromes.
Infusion of Stem Cell Products
Contaminated HSC Products
All stem cell products were infused on the patient care unit. Cryopreserved products were transported to
Thirty-six (1.2%) of the 2935 HSC products were contaminated with microorganisms. The stem cell
RESULTS Patient Characteristics
Table 1. Microbially Contaminated Stem Cell Products
HSC Product
Preprocessing*
Postprocessing*
At Thaw*
Total
Total HSC Products†
Incidence of Contamination (%)
BM Allogeneic Autologous PBSC Allogeneic Autologous UCB Related Unrelated Total
13 10 3 4 1 3 3 3 0 20
9 5 4 2 0 2 4 2 2 15
1 0 1 0 0 0 0 0 0 1
22 15 8 6 1 5 7 5 2 36
1666 1257 409 919 296 623 350 18 332 2935
1.3 1.2 2.0 0.7 0.3 0.8 2.0 27.8 0.6 1.2
HSC indicates hematopoietic stem cell; BM, bone marrow; PBSC, peripheral blood stem cell; UCB, umbilical cord blood. *Phase in processing when contamination occurred. †Total number of the type of product infused at our center during study period.
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Microbial Contamination of HSC Products
sources of contaminated products are listed in Table 1. BM accounted for 22 (61%) of the 36 contaminated products. Of the 3 types of HSC products, UCB had the highest incidence of contamination at 2.0%. The phase when contamination occurred was identified upon review of processing records (Table 1). Twenty (55%) products had contamination identified before processing, 15 (42%) after processing, and 1 (3%) was identified after a bag break of autologous BM at the time of thaw. Of the 20 contaminated products identified before processing, 13 were BM, 4 were PBSCs, and 3 were UCB. Of the 15 products contaminated as a result of product processing, 9 were BM, 2 were PBSCs, and 4 were UCB; 9 products were minimally manipulated and 6 were extensively manipulated during processing. Six patients received contaminated autologous PBSC. Of these 6 patients, 5 had collection through a central venous catheter and 1 through antecubital veins. Two of the patients with central venous catheters had CNS bacteremia during the time of apheresis; 1 of these products was found to be microbially contaminated with CNS before processing and 1 was contaminated after processing. Microbial Organisms
Seventeen different bacterial or fungal organisms were found to be contaminants (Table 2). CNS was the most common isolate and was found in 19 HSC products. Bacillus was the next most frequent, being found in 4 products. Gram-negative organisms and mold/fungi were uncommon. Clinical Outcomes
Of the 35 patients who received contaminated products, 34 had benign clinical courses. Antibiotics
were changed in response to information received about the contaminated product for 16 patients; for the remaining 19 patients, the prescribed antibiotics were deemed appropriate or not commented on in the medical record. One patient was infused with Klebsiella pneumonia and Escherichia coli from a related UCB. This was known at infusion, and the patient was begun on ceftazidime and trimethoprim/sulfa based on antibiotic sensitivity results. This patient had only 2 febrile episodes (days 6 and 8 after infusion) with no serious clinical sequelae and no positive blood cultures in the first 14 days after infusion. Nine of the 35 patients subsequently developed positive blood (n ⫽ 8) or bile (n ⫽ 1) cultures within 14 days after transplantation (Table 3). Blood culture isolates were identical to the infused species in 2 patients, different in 6 patients, and unknown (antibiotic sensitivity results unknown) in 1 patient. At the time of stem cell infusion, all patients were on prophylactic antibiotics or being treated for an already isolated microorganism. Antibiotics were added or changed in 5 patients due to reporting of the positive stem cell product, documentation was unclear in 2 patients, and 2 patients had no modification in antibiotics. Of the 9 HSC products, 3 were identified as being contaminated before processing and 6 after processing. Of these 6 postprocessing events, 4 products underwent minimal and 2 extensive processing. Of the 4 products that underwent minimal processing, 3 were cryopreserved products (1 autologous PBSC, 1 related UCB, and 1 unrelated UCB) and 1 was an unrelated BM that was not manipulated. The unrelated UCB also underwent washing. Of the 2 extensively manipulated products, both were autologous BM products that underwent incubation with interferon-␥. One product was also subject to a buffy coat preparation. The other
Table 2. Contaminating Organisms and Stem Cell Products Organism
Contaminated Products (n)*
HSC Product (n)
Coagulase-negative Staphylococcus Bacillus sp Bacillus cereus Aerococcus sp ␣-Hemolytic streptococcus Aspergillus fumigata Bacteroides vulgatus Bifidobacterium sp Candida parasilopsis Clostridium sp, not perfringens Corynebacterium sp Escherichia coli Gram-positive cocci in clusters, not otherwise specified Klebsiella pneumonia Non-group D enterococcus sp Peptostreptococcus sp Pseudomonas cepacia Total
19 3 1 1 1 1 1 1 1 1 2 1 1 1 1 1 1 38
BM (12), PBSC (5), UCB (2) BM (2), PBSC (1) BM PBSC BM BM UCB UCB BM UCB BM (2) UCB BM UCB UCB UCB BM
HSC indicates hematopoietic stem cell; BM, bone marrow; PBSC, peripheral blood stem cell; UCB, umbilical cord blood. *More than 1 organism contaminated 3 products.
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Table 3. Summary of Patients with Post-transplantation Positive Blood Cultures
Stem Cell Source
Phase Contamination Occurred/Degree of Manipulation
Stem Cell Isolate
Blood Culture Isolate
Strain
Change in Antibiotics in Response to Contaminated Stem Cells
Autologous PBSC Postprocessing/minimal CNS CNS Same Vancomycin added Unrelated BM Postprocessing/minimal CNS CNS Unknown None—already on vancomycin Autologous BM Postprocessing/extensive Pseudomonas cepacia Pseudomonas cepacia Same Trimethoprim/sulfamethoxazole added Unrelated BM Preprocessing CNS Candida tropicalis Different None—already on vancomycin Autologous BM Postprocessing/extensive Corynebacterium sp Pseudomonas Different Unknown aeruginosa Unrelated UCB Postprocessing/minimal CNS Candida krusei Different Changed from cefazolin to vancomycin Autologous PBSC Preprocessing CNS CNS in bile Different Vancomycin added Related UCB Postprocessing/minimal CNS VRE and group D Different Unknown enterococcus Allogeneic PBSC Preprocessing Aerococcus sp 1. CNS Different Vancomycin added 2. ␣-Hemolytic streptococcus 3. Moraxella sp 4. Proteus mirabilis
CNS indicates coagulase-negative Staphylococcus; BM, bone marrow; PBSC, peripheral blood stem cells; UCB, umbilical cord blood; VRE, vancomycin resistant enterococcus.
product had a mononuclear cell preparation centrifugation step; the patient who received this product is described below. One patient who underwent a myeloablative autologous BM transplantation in 1991 died of complications from sepsis. At the time of BM harvest, the patient was clinically well and cultures obtained after collection/before processing were negative. The BM product was extensively manipulated and purged with interferon-␥, a process that included ⱖ8 steps, many in open systems. Pseudomonas cepacia was isolated from the BM product after processing and from blood cultures obtained from the patient after transplantation (Table 4). When culture results of the HSC product became known, the patient had already received pretransplantation conditioning and no other source of HSC was available. Based on antibiotic sensitivity testing, the patient was placed on trimethoprim/sulfamethoxazole and piperacillin 3 days before infusion. Acetaminophen, lorazepam, and hydrocortisone were
administered before infusion of the product. During infusion the patient became unresponsive, hypotensive, and bradycardic. After the patient was resuscitated with intravenous fluids, 3 more doses of hydrocortisone were administered in conjunction with diphenhydramine, and the remaining product was infused uneventfully. Later on the day of transplantation, the patient became febrile, tachypneic, complained of chest pain, and had a decline in urine output. By the next day, vasopressors were required to maintain an adequate blood pressure, and right atrial catheter readings were consistent with septic shock. Disseminated intravascular coagulation, renal failure, and respiratory failure ensued. Pseudomonas cepacia grew from patient blood cultures obtained on post-transplantation days 2 and 3 that had the same antimicrobial sensitivities as the HSC product isolate (Table 4). The patient died on post-transplantation day 7 from multiorgan failure.
Table 4. Sensitivities of Pseudomonas cepacia by Site Antibiotic
Bone Marrow
Blood
Amikacin Cefoperazone Cefotaxime Chloramphenicol Gentamicin Mezlocillin Piperacillin Tetracycline Ticarcillin Tobramycin Trimethoprim/sulfamethoxazole
R R I R R R S R R R S
R R R I R R S R R R S
I indicates intermediate; R, resistant; S, sensitive.
DISCUSSION We report the type and incidence of microbial contamination, phase of processing during which contamination occurred, and the clinical sequelae of infusing contaminated stem cell products at a single institution over the course of 14 years. In total, 2935 HSC products, including 350 UCB, were infused during the study period, with an overall 1.2% incidence of contamination. The organisms isolated in the stem cell products were predominantly skin-colonizing organisms and water-borne organisms, which is consistent with previous reports [1-19].
Microbial Contamination of HSC Products
The reported incidence of stem cell contamination rates is 0%-45% [1-19]. This wide range is likely influenced by multiple factors, including stem cell source, collection technique, extent of product manipulation, and center size. Over time, the source of stem cells has changed, with BM being the predominant HSC source in the early 1980s. BM is collected in the operating room under sterile conditions; however, the collection system in the 1980s consisted of multiple open containers. Ultimately, a closed system with an inline series of filters was developed. By the late 1980s and early 1990s, PBSCs emerged and have remained a primary HSC source. Central venous catheters, although convenient for apheresis, have a propensity to become infected in neutropenic, immunocompromised patients and are a source of PBSC product contamination. Most recently, UCB has emerged as a source of stem cells. The first UCB transplants were performed from related donors at a time when, now antiquated, open-system collection techniques were employed; collectors had little training, and if the product was microbially contaminated, it was typically used by necessity. Currently, UCB stem cells are collected with a closedsystem technique and, in the case of public UCB banks, those products that are microbially contaminated are not typically entered into usable inventory. A thorough review of the laboratory procedural records of the contaminated products was conducted for this study in an effort to identify the sources of contamination. About 50% of the products were contaminated before receipt into the laboratory. These BM and PBSC products were most likely contaminated during collection due to inadequate aseptic technique of the skin before puncture, because skin contaminants comprised most of the organisms identified from these products. After collection, even minimal manipulation resulted in contamination; however, the degree of product manipulation was likely a critical factor in the rate of stem cell contamination. Although all transfers of cells were performed in biological safety cabinets using sterile disposable syringes, tubing, and bags, the potential remained for introducing contamination at each processing step by failure to use proper aseptic techniques. Our patient who succumbed to complications from sepsis received an autologous BM that had undergone extensive manipulation that included ⱖ8 steps, many of which were in open systems. Although the small number of contaminated products in our study precludes a formal analysis of any correlation between contamination rates and degree of product manipulation, we recommend that physicians caring for patients who receive products that undergo multiple manipulations have a heightened awareness of the possibility of infusion of contaminated products. Skin, reagents, processing steps, and equipment such as water baths, incubators, and centrifuges have
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been shown to be potential sources of contamination [1-19]. Hirji et al [17] described an outbreak in stem cell products in which Actinomycete was isolated; a change in protocol significantly decreased contamination rates. In that report, examination of the collection, processing, and administration process yielded no breaks in the infection-control technique at reinfusion, and cultures of the equipment, staff hands, potted plants, water bath, and LN2 tanks did not yield the outbreak isolate. Eventually, evaluation of the cryopreservation process revealed multiple potential sources of contamination, including using a multipleuse bottle for cryopreservation media, cleaning of laminar flow hoods only at the end of the day, blockage of the laminar flow hood air filter, and using a sterile syringe to gain entry to media bottles multiple times instead of using sterile pipettes only once. Multiple changes in processing were implemented, and subsequently, no additional contamination of products with the outbreak strain occurred. During the period of review for this study, cellprocessing laboratories have witnessed the evolution and integration of regulations and standards by the FDA and professional organizations such as the American Association of Blood Banks and the Foundation for the Accreditation of Cellular Therapy. The FDA only recently (May 2005) introduced its first regulations for somatic cell and tissue products, known as current good tissue practices [22]. These regulations and those of the American Association of Blood Banks and the Foundation for the Accreditation of Cellular Therapy primarily focus on patient and product safety and mandate that laboratories and collection facilities operate under clean and sanitary conditions and demonstrate a level of environmental control that minimizes the risk for the introduction of contaminants. Approximately equal numbers of patients in our study had contamination detected before and after processing. However, the change in sterility testing protocol implemented during the study period may have skewed these results by erroneously suggesting a higher rate of contamination due to processing. It is also possible that contamination occurring from the time of collection evaded postcollection detection and was isolated only after processing. Expertise of donor center and laboratory personnel may also vary among collection centers and affect contamination rates. Previous studies have reported a total number of 100 to ⬎2000 stem cell products processed by individual centers [1-19]. It is conceivable that personnel at larger centers have more training and expertise, with a resultant decreased possibility of contamination of products during collection and processing. Four previous studies have reported patients with post-transplantation blood cultures positive for the
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same strain as the infused product [12,15,19,20]. In those reports, CNS and P cepacia were isolated. However, no significant clinical sequelae resulted. Webb et al [12] reported that 2 of 73 patients developed fever and positive blood cultures. One patient had P cepacia isolated from the infused product at 48 hours after infusion and in subsequent blood cultures at 72 hours after infusion. The isolates had identical antibiotic sensitivities. The second patient had Staphylococcus epidermidis isolated from the infusion product and blood cultures. In an analysis by Schwella et al [15] of 38 patients who received contaminated autologous BM , 5 had BM and subsequent post-transplantation isolates grew CNS. Larrea et al [19] reported on 28 patients who received contaminated products. Nine of 19 patients developing fever after transplantation had positive blood cultures; 3 patients were bacteremic with a CNS isolate identical to that of the infused contaminant. A case report by Nifong et al [20] was of a patient who received an autologous PBSC transplant contaminated with CNS. The patient had an identical organism isolated on blood cultures after product infusion. The patient had been on prophylactic antibiotics and no serious clinical sequelae ensued. We describe the only other reported case of a product contaminated with P cepacia resulting in posttransplantation positive patient blood cultures with the same strain of organism. Although the patient developed side effects from the infusion itself, these may have been due, at least in part, to the lack of diphenhydramine as part of the prescribed premedications. Despite initiation of appropriate antibiotics before infusion of the product, the patient ultimately died. This is the only reported death presumed due to an infused contaminated stem cell product. The phase of processing when contamination occurred was most likely during processing, because cultures obtained after collection/before processing were negative. Although the incidence of contaminated HSC products is low, steps to prevent contamination should continue to be employed at all times. To prevent contamination by skin organisms during the collection of PBSC with central catheters or peripheral lines, a technique of diversion and disposal of the first few milliliters to eliminate the skin-plug phenomenon has been suggested [23]. When possible, only closed collection systems should be used, the number of manipulation steps should be kept to an absolute minimum, and personnel should undergo routine training in the aseptic techniques of collection and processing of HSC products. Serious clinical sequelae from contaminated stem cell products are rare. Skin flora contaminants are likely to be innocuous or covered by prophylactic antibiotics as part of many transplantation center protocols. In contrast, we recommend that prophylactic antibiotics always be administered when HSC prod-
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ucts are contaminated with gram-negative organisms or that, if possible, an alternative HSC product be chosen.
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17. Hirji Z, Saragosa R, Dedier H, et al. Contamination of bone marrow products with an actinomycete resembling microbacterium species and reinfusion into autologous stem cell and bone marrow transplant recipients. Clin Infect Dis. 2003;36: e115-e121. 18. Kamble R, Pant S, Selby GB, et al. Microbial contamination of hematopoietic progenitor cell grafts-incidence, clinical outcome, and cost-effectiveness: an analysis of 735 grafts. Transfusion. 2005;45:874-878. 19. Larrea L, de La Rubia J, Soler MA, et al. Quality control of bacterial contamination in autologous peripheral blood stem cells for transplantation. Haematologica. 2004;89:1232-1237. 20. Nifong TP, Ehmann WC, Mierski JA, Domen RE, Rybka WB. Favorable outcome after infusion of coagulase-negative staph-
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ylococci-contaminated peripheral blood hematopoietic cells for autologous transplantation. Arch Pathol Lab Med. 2003;127: e19-e21. 21. Brecher ME, ed. American Association of Blood Banks Technical Manual. 13th ed. Bethesda, MD: American Association of Blood Banks; 2005. 22. Current good tissue practice for human cell, tissue and cellular and tissue-based products establishments; inspection and enforcement; final rule. FDA 21 CFR parts 16, 1270 and 1271, docket no. 1997N-484P. Fed Reg. 2004;69(226). 23. Wagner SJ, Robinette D, Friedman LI, Miripol J. Diversion of initial blood flow to prevent whole-blood contamination by skin surface bacteria: an in vitro model. Transfusion. 2000;40: 335-338.
