Sources and sequelae of bacterial contamination of hematopoietic stem cell components: implications for the safety of hematotherapy and graft engineering

Successful autologous hematopoietic stem cell transplants using Salmonella positive products collected from asymptomatic donors

BACKGROUND

Bacterial contamination of hematopoietic stem cell (HSC) products is most commonly due to normal skin flora. Salmonella in HSC products is rare, and to our knowledge safe administration of an autologous HSC product containing Salmonella has not been reported.

STUDY DESIGN AND METHODS

We describe two patients undergoing autologous HSC transplant: peripheral blood HSC collection was performed by leukapheresis, and samples were cultured according to standard institutional protocol. Subsequent microorganism identification was performed using MALDI-TOF (Bruker Biotyper). Strain-relatedness was investigated by infrared spectroscopy using the IR Biotyper (Bruker).

RESULTS

The patients were asymptomatic throughout the collection process; however, HSC products collected on two consecutive days from each patient were positive for Salmonella. Isolates from both cultures were further characterized as Salmonella enterica serovar Dublin by the local public health department. Antibiotic susceptibility testing revealed different sensitivity patterns for the two strains. IR Biotyper demonstrated significant discriminatory power among the clinically significant Salmonella enterica subspecies, serogroups B, C1, and D. The patient strains were similar as both belonged to Group D Salmonella enterica serovar Dublin but were not identical. The Salmonella positive autologous HSC products were infused to both patients following administration of empiric antibiotic therapy. Both patients successfully engrafted and did well.

CONCLUSION

Salmonella is rarely seen in cellular therapy products and positivity may be the result of asymptomatic bacteremia at the time of collection. We present two instances of autologous HSC products containing Salmonella that were infused, along with prophylactic antimicrobial therapy without significant adverse clinical effects.

Effects of cryopreservation on gram-positive bacteria contaminants in umbilical cord blood

OBJECTIVE

To evaluate the effects of cryopreservation in post-thaw umbilical cord blood units for the survivability of Gram-positive bacteria strains.

BACKGROUND

Microbial screening is required for all cord blood units (CBUs). Four gram-positive contaminants were documented to survive cryopreservation poorly and isolation of other contaminants were reported.

METHODS

Forty-eight contaminated CBUs detected with either Staphylococcus epidermidis, Corynebacterium species, Peptostreptococcus or Streptococcus species before cryopreservation were used in this study. CBUs were processed, DMSO-infused and microbial screened before cryopreservation. Post-thaw microbial screening was achieved using 1 and 10 ml inoculants in BACTEC culture bottles. Positive bottles were subjected for microbial identification and results were compared with those from pre-freeze.

RESULTS

A higher rate of microbial contamination was found using the 10 ml inoculant. Screening of 11 CBUs did not detect any contaminants while 30 CBUs screened detected more than one unknown contaminants and majority of contaminants were identified to be gram-negative species.

CONCLUSION

A higher inoculation volume used at post-thaw for microbial screening improves contamination detection but leads to the loss of precious cord blood. Some contaminants did not survive cryopreservation or were not identified due to their low microbial levels. Contrasting contaminants found at post-thaw suggest the improvements made in detection and identification of contaminants over the years.

Impact of microbial contamination of haematopoietic stem cells on post-transplant outcomes: A retrospective study from tertiary care centre in India

BACKGROUND

Haematopoietic stem cells (HSC) may act as a source of infection for the recipient due to manipulation at multiple levels from collection to infusion. Due to the high risk of contamination cultures are usually taken during multiple steps. The clinical significance of microbial contamination of HSC on the post-transplant course and the role of prophylactic antibiotics is relatively unknown.

AIMS AND METHODS

The aim of our study is to investigate the incidence of microbial contamination of haematopoietic stem cell and to assess its impact on the post-transplant febrile neutropenia, engraftment kinetics, hospitalisation and day 100 mortality. Details of all patients admitted in the bone marrow transplantation unit of a tertiary care centre in India between January 2014 and December 2018 were collected from case records.

RESULTS

Of the 1306 stem cell harvests from 503 patients sent for culture, 17 harvests (1.3%) were found to have a culture positive report. Sixteen patients had undergone autologous transplant. Multiple myeloma was most common indication of HSC transplant followed by Non-Hodgkin Lymphoma (NHL). Twelve of 17 HSC cultures were positive at the time of infusion and five were positive at the time of harvest. The five HSC that were culture positive at the time of harvest were culture negative at the time of infusion. Gram-positive organisms were isolated in six cultures and gram-negative in rest. All patients developed febrile neutropenia post-transplantation between day 1 and day 7. The median time of onset of fever was day +5 (1-7), the median duration of fever was 4 days (2-7), the median duration of antibiotic use was 11 days (9-16). Median day for neutrophil engraftment was 11 days (9-16), the median day for platelet engraftment was 14 days (10-25) and median duration of hospitalisation was 15 days (12-78). All patients were alive at day 100 of transplant.

CONCLUSION

This study shows that there appears to be minimal impact of culture positive HSC on transplant related outcomes in terms of engraftment kinetics, duration of hospitalisation and day 100 mortality. Discarding of contaminated HSC may not be required, though on development of febrile neutropenia appropriate antibiotics should be administered based on sensitivity pattern of HSC culture. Larger prospective studies are needed to determine the clinical relevance of such contaminations. Emphasis should be laid on better infection control practices to minimise contamination rates.

Prevalence and significance of bacterial contamination of autologous stem cell products

There is limited and conflicting information on the prevalence of contamination of haematopoietic stem and progenitor cell products (HPCPs), and their optimal management remains unclear. The authors reviewed the microbial surveillance data of HPCPs collected between January 2002 and December 2019 for autologous transplantation at the study institution to determine the prevalence of microbial contamination and the potential infectious complications among recipients. Among 3935 HPCPs, 25 (0.6%) were contaminated. Ultimately, 22 patients received contaminated grafts, with pre-emptive antimicrobial therapy initiated in six of these patients. No patients developed subsequent infectious complications. These data suggest that microbial contamination of autologous HPCPs and associated adverse outcomes are rare.

Improved harmonization of critical characterization assays across cell therapies

The field of cell therapy has blossomed, providing exciting new options for treating a variety of diseases. While few cell therapy products have US FDA approval, there are thousands of cell treatments at various stages of development, pointing to a potential revolutionary shift in patient care. The expanding number and nature of cellular therapies necessitate greater standardization. Several international organizations are collaborating to pursue some level of global standardization, especially concerning cell banking. However, less harmonization surrounds assays used for critical quality characterization including: identity, purity, safety and potency. Frequently, there is divergence regarding the terms describing the characterization assays across regulatory authorities and guidances. This review summarizes the critical quality assays currently used for different categories of cell therapies. Areas of harmonization and an absence of standardization are highlighted. We propose potential solutions to facilitate harmonization of critical quality characterization assays and the language used to describe them.

Sterility release testing of peripheral blood stem cells for transplantation: impact of culture bottles and incubation temperature

BACKGROUND

Sterility testing of peripheral blood stem cells (PBSCs) is mandatory before release. As antibiotic treatment of the PBSC donor may result in false-negative results, PBSC matrix validation must be carried out.

STUDY DESIGN AND METHODS

Three spiked PBSCs and a buffy coat (BC; control matrix) were analyzed using the blood culture device BacT/ALERT 3D with the low-temperature module. Samples were spiked with Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Candida albicans, Aspergillus brasiliensis, Clostridium sporogenes, and Propionibacterium acnes. Standard iAST/iNST culture bottles and iFA/iFN Plus bottles, which include resorbing polymers, were incubated for 14 days. All aerobic bottles were incubated at 22.5°C and for a direct comparison also at 35°C while all anaerobic bottles were incubated at 35°C.

RESULTS

The BacT/ALERT 3D system detected all microbes in iAST/iNST culture bottles according to their growth behavior in the BC matrix. Detection of microbes differed significantly in PBSC products using standard iAST/iNST culture bottles and iFA/iFN Plus bottles with resorbing polymers: In Graft 1 no growth was detected in spiked bottles with S. aureus (iAST), B. subtilis (iAST/iNST), C. sporogenes (iNST), and P. acnes (iNST) compared to iFA Plus and iFN Plus bottles wherein growth of spiked microbes was confirmed. Graft 2, with another antibiotic treatment, showed no growth in iAST/iNST bottles spiked with P. aeruginosa, B. subtilis, and C. sporogenes. However, using iFA/iFN Plus bottles all spiked microbes were detectable. The comparison of incubation temperature showed an expected slower growth at 22.5°C.

CONCLUSION

The use of iFA/iFN Plus culture bottles incubated at different temperatures safely detected microbes in spiked PBSCs.

Does microbial contamination influence the success of the hematopoietic cell transplantation outcomes?

INTRODUCTION

Microbial contamination can be a marker for faulty process and is assumed to play an important role in the collection of hematopoietic progenitor cell (HPC) and infusion procedure. We aimed to determine the microbial contamination rates and evaluate the success of hematopoietic cell transplantation (HCT) in patients who received contaminated products.

PATIENTS-METHODS

We analyzed microbial contamination records of HPC grafts between 2012 and 2015, retrospectively. Contamination rates of autologous donors were evaluated for at three steps: at the end of mobilization, following processing with dimethyl sulfoxide, and just before stem cell infusion. Grafts of allogeneic donors were assessed only before HCT.

RESULT

A total of 445 mobilization procedures were carried out on 333 (167 autologous and 166 allogeneic) donors. The microbiological contamination of peripheral blood (323/333 donations) and bone marrow (10/333 donations) products were analyzed. Bacterial contamination was detected in 18 of 1552 (1.15 %) culture bottles of 333 donors. During the study period 248 patients underwent HCT and among these patients microbial contamination rate on sample basis was 1.3 % (16/1212). Microbial contamination detected in nine patients (7 autologous; 2 allogeneic). In 8 of 9 patients, a febrile neutropenic attack was observed. The median day for the neutropenic fever was 4 days (0-9). None of the patients died within the post-transplant 30 days who received contaminated products.

CONCLUSION

The use of contaminated products with antibiotic prophylaxis may be safe in terms of the first day of fever, duration of fever, neutrophil, platelet engraftment and duration of hospitalization.

Effects of storage temperature on hematopoietic stability and microbial safety of BM aspirates

Bone marrow (BM) remains a common source for hematopoietic SCT. Due to the transcutaneous approach, contamination with skin bacteria is common. The delay between harvest and transfusion can be considerable, potentially allowing for bacterial proliferation. The optimal transportation temperature, specifically with respect to bacterial growth and consequences thereof for hematopoietic quality, remain undefined. For 72 h, 66 individual BM samples, non-spiked/spiked with different bacteria, stored at 20-24 °C room temperature (RT) or 3-5 °C (cold), were serially analyzed for hematopoietic quality and microbial burden. Under most conditions, hematopoietic quality of BM was equal or better at RT: Typical BM contaminants (P. acnes and S. epidermidis) and E. coli were killed or bacterial proliferation was arrested at RT; hematopoietic quality was not impacted by the contamination. However, several pathogenic bacteria not typically found in BM (S. aureus and K. pneumoniae) proliferated dramatically at RT and impaired hematopoietic quality. Bacterial proliferation was arrested in the cold. The overwhelming majority of BM samples, that is, those that are sterile or contaminated only with skin commensals, will benefit from transportation at RT. Those bacteria that proliferate and perturb hematopoietic quality are not typically found in BM. Our data support recommendations for RT transportation and storage of BM.

Bacterial safety of cell-based therapeutic preparations, focusing on haematopoietic progenitor cells

Bacterial safety of cellular preparations, especially haematopoietic progenitor cells (HPCs), as well as advanced therapy medicinal products (ATMPs) derived from stem cells of various origins, present a challenge for physicians, manufacturers and regulators. The article describes the background and practical issues in this area and illustrates why sterility of these products cannot currently be guaranteed. Advantages and limitations of approaches both for classical sterility testing and for microbiological control using automated culture systems are discussed. The review considers novel approaches for growth-based rapid microbiological control with high sensitivity and faster availability of results, as well as new methods for rapid bacterial detection in cellular preparations enabling meaningful information about product contamination within one to two hours. Generally, however, these direct rapid methods are less sensitive and have greater sampling error compared with the growth-based methods. Opportunities for pyrogen testing of cell therapeutics are also discussed. There is an urgent need for development of novel principles and methods applicable to bacterial safety of cellular therapeutics. We also need a major shift in approach from the traditional view of sterility evaluation (identify anything and everything) to a new thinking about how to find what is clinically relevant within the time frame available for the special clinical circumstances in which these products are used. The review concludes with recommendations for optimization of microbiological control of cellular preparations, focusing on HPCs.

Effects of cryopreservation on microbial-contaminated cord blood

BACKGROUND

Cord blood units (CBUs) are associated with significant risk of exposure to microbial contamination during collection and processing; however, the survival of bacteria within a CBU is poorly understood. This study aimed to determine whether contaminating organisms in CBU survive the cryopreservation, frozen storage, and subsequent thawing conditions before infusion.

STUDY DESIGN AND METHODS

A total of 134 CBUs rejected from banking due to known contamination were thawed and rescreened using blood culture bottles (BacT/ALERT, bioMérieux). An additional 61 fresh CBUs were deliberately spiked with a range of microbial organisms and evaluated both before freeze and after thaw.

RESULTS

Microbial contaminants were detected after thaw in 63% of stored contaminated CBUs and 85% of spiked CBUs. Postthaw organism detection in spiked cord blood (CB) was higher in adult culture bottles (80%) than pediatric culture bottles (61%). Twenty percent of spiked organisms, particularly Bacillus subtilis, Escherichia coli, Clostridium sporogenes, and Propionibacterium acnes, were not detected in prefreeze samples but were detectable after thaw.

CONCLUSIONS

This study demonstrates that the majority of contaminating organisms isolated in a prefreeze sample of CB have the ability to survive cryopreservation, frozen storage, and thawing. Further, CBUs reported as microbial free may contain microbial contamination, which could result in transplantation of contaminated CB and be potentially deleterious to a patient.

Microbial contamination of hematopoietic progenitor cell products

INTRODUCTION

Microbial screening for contamination is a part of hematopoietic progenitor cell (HPC) collection and infusion procedure. We aimed to find out our microbial contamination rates during collection, processing and infusion steps of HPC products. We also evaluated the clinical course of patients who received contaminated HPC products.

PATIENTS-METHODS

We retrospectively analyzed microbial contamination records of HPC grafts between 2010 and 2012. HPC products of autologous donors were evaluated for contamination at three steps: at the end of mobilization, following processing with DMSO and just before stem cell infusion. Grafts of allogeneic donors were assessed only before HPC transplantation (HCT). Microbiological analysis of HPC samples were performed with an automated system (BacT/Alert®).

RESULT

During the study period a total of 492 mobilization procedures were performed on 329 (214 autologous and 115 allogeneic) donors. Bacterial contamination has been detected in 103 of 1630 samples (6%). Ninety-seven out of 1162 blood samples (8%) from 265 patients who were treated with HCT were contaminated. Forty-six patients (41 autologous and 5 allogeneic) were transplanted with contaminated HPC products. During HCT 42 patients experienced febrile neutropenic attack and 34 of them had positive blood culture results. In none of these 34 patients the isolated pathogens were the same organisms with those found in the final contaminated stem cell product before stem cell infusion. None of the patients who received contaminated products died because of sepsis within the posttransplant 30days. There was no significant difference between patients who received contaminated and non-contaminated products in terms of the first day of fever, duration of fever, engraftment kinetics and duration of hospitalization.

CONCLUSION

Our results suggest that microbial contamination of HPC products is an issue to be prevented, although it may not have a major impact on the general success of HCT.

Microbial contamination of hematopoietic progenitor and other regenerative cells used in transplantation and regenerative medicine

BACKGROUND

Microbial contamination of hematopoietic progenitor cells (HPCs) and other regenerative cells used in transplantation and regenerative medicine can occur during collection and after in vitro manipulation, including purging, cryopreservation, thawing, and infusion.

STUDY DESIGN AND METHODS

Microbiologic culture findings on consecutive HPCs and other cell preparations at a single institution derived from peripheral blood, marrow, cord blood, and mesenchymal stromal cells during all phases of manipulation were retrospectively examined from 2005 through 2011. Results were classified as confirmed positive, false positive, and indeterminate.

RESULTS

During the 6-year surveillance period, 365 patients underwent 912 procedures involving HPC or other cell-based transfusion. True positive microbial contamination was found in five of 663 (0.8%) peripheral blood and two of 34 (5.9%) marrow preparations (p = 0.04), while no contamination was found in 118 preparations from other sources. True-positive microbial contaminants included coagulase-negative staphylococci in autologous HPC products derived from peripheral blood from two patients with asymptomatic central venous catheter infections at time of apheresis and Propionibacterium acnes in one apheresis and two marrow products. Organism loads were low in all cases (≤500 colony-forming units/mL), and no adverse sequelae occurred in four patients that received contaminated products.

CONCLUSION

The incidence of microbial contamination of progenitor cell products in our institution over a 6-year period was low (0.8% overall), with contaminants originating from infected central venous catheters or from skin flora. All contaminants were bacterial species of low virulence, present in low titers and, if transfused, did not result in adverse reactions.

Monitoring mitochondrial inner membrane potential for detecting early changes in viability of bacterium-infected human bone marrow-derived mesenchymal stem cells

Introduction

One of the most challenging safety issues in the manufacture of cell based medicinal products is the control of microbial risk as cell-based products cannot undergo terminal sterilization. Accordingly, sensitive and reliable methods for detection of microbial contamination are called for. As mitochondrial function has been shown to correlate with the viability and functionality of human mesenchymal stem cells (hMSCs) we have studied the use of a mitochondrial inner membrane potential sensitive dye for detecting changes in the function of mitochondria following infection by bacteria.

Methods

The effect of bacterial contamination on the viability of bone marrow-derived mesenchymal stem cells (BMMSCs) was studied. BMMSC lines were infected with three different bacterial species, namely two strains of Pseudomonas aeruginosa, three strains of Staphylococcus aureus, and three strains of Staphylococcus epidermidis. The changes in viability of the BMMSCs after bacterial infection were studied by staining with Trypan blue, by morphological analysis and by monitoring of the mitochondrial inner membrane potential.

Results

Microscopy and viability assessment by Trypan blue staining showed that even the lowest bacterial inocula caused total dissipation of BMMSCs within 24 hours of infection, similar to the effects seen with bacterial loads which were several magnitudes higher. The first significant signs of damage induced by the pathogens became evident after 6 hours of infection. Early changes in mitochondrial inner membrane potential of BMMSCs were evident after 4 hours of infection even though no visible changes in viability of the BMMSCs could be seen.

Conclusions

Even low levels of bacterial contamination can cause a significant change in the viability of BMMSCs. Moreover, monitoring the depolarization of the mitochondrial inner membrane potential may provide a rapid tool for early detection of cellular damage induced by microbial infection. Accordingly, mitochondrial analyses offer sensitive tools for quality control and monitoring of safety and efficacy of cellular therapy products.

Bacillus cereus septicemia attributed to a matched unrelated bone marrow transplant

BACKGROUND

Hematopoietic cell transplantation (HCT) is performed in more than 25,000 patients annually. Clinically significant bacterial transmission from HCT products is rare.

CASE REPORT

A 36-year-old male of Asian descent with chronic myelogenous leukemia developed sepsis leading to acute renal failure and disseminated intravascular coagulation during infusion of matched unrelated donor bone marrow. This product later tested positive for Bacillus cereus.

DISCUSSION

This HCT product traveled 31 hours at room temperature before arriving at the transplant center. Reducing transport times, transporting at 4 °C, and enhancing bacterial surveillance of HCT products may increase the ability to detect bacterial proliferation from transport.

CONCLUSION

To prevent a similar case in the future, we will begin Gram staining all HCT products in transit more than 24 hours to alert physicians of the need for prophylactic antibiotic therapy.

Packaging Considerations for Biopreservation

SUMMARY: The packaging system chosen for biopreservation is critical for many reasons. An ideal biopreservation container system must provide for closure integrity, sample stability and ready access to the preserved material. This means the system needs to be hermetically sealed to ensure integrity of the specimen is maintained throughout processing, storage and distribution; the system must remain stable over long periods of time as many biobanked samples may be stored indefinitely; and functionally closed access systems must be used to avoid contamination upon sample withdraw. This study reviews the suitability of a new commercially available vial configuration container utilizing blood bag style closure and access systems that can be hermetically sealed and remain stable through cryopreservation and biobanking procedures. This vial based systems allow for current good manufacturing/tissue practice (cGTP) requirements during processing of samples and may provide the benefit of ease of delivery by a care giver. In this study, the CellSeal® closed system cryovial was evaluated and compared to standard screw cap vials. The CellSeal system was evaluated for durability, closure integrity through transportation and maintenance of functional viability of a cryopreserved mesenchymal stem cell model. The results of this initial proof-of-concept study indicated that the CellSeal vials are highly suitable for biopreservation and biobanking, and provide a suitable container system for clinical and commercial cell therapy products frozen in small volumes.

Predictors of high yield and purify of CD34(+) cell-selected PBPC, collected from patients with multiple myeloma

BACKGROUND

Wide ranges i n cell recovery and purity may be observed following CD34(+) cell selection of mobilized HPC componetns. Characteristics of the mobilized HPC, associated with isolation of a high CD34(+) cell yield and purity following cell selection, have yet to be defined.

METHODS

Cell number and purities were determined before and after 56 CD34(+) cell-selection procedures, performed using the CellPro Ceprate SC system from April 1997 to February 1998. HPC were collected from 28 patients with multiple myeloma, following cyclophosphamide (60mg/kg) and G-CSF (10microg/kg) mobilization.

RESULTS

A medium of 47.9% (range 1.5-109.6%) CD34(+) cells were recovered in the enriched (ENR) fraction. A linear correlation existed between total CD34(+) cells in the ENR fraction and total CD34(+) cells in the START fraction (R2=0.93); there was a logarithmic correlation between CD34 ENR fraction purity and START fraction purity (R2=0.73). A START CD34(+) cell purity > 0.42% improved purity in the ENR fraction. A median of one (range one to nine) procedure was required to isolate 2 x 10 6 CD34(+) cells/kg. Three patients pretreated with alkylating agents failed to mobilized adequate numbers of HPC.

DISCUSSION

Isolation of highly purified CD34(+) cell-selected components using the Ceprate SC system in dependent on the CD34(+) purity of the lekapheresis component collected. Mobilization regimens should be used to maximize CD34(+) cell purity in stem cell authografts if CD34(+) cell selection is to be performed. Similar strategies should be used to evaluate other cell-selection devices as they become available.

Microbiological analysis of cryopreserved human heart valves after storage: a survey of 3 banks in Spain

Several reports have shown liquid nitrogen containers as not being sterile. Microorganism transmission has been observed in different cells and tissues stored under this condition, but there is no data on contamination of stored human valves. We performed a survey on heart valve banking in Spain. Regarding the questionnaire, we have a complete microbiological analysis of 304 thawed tissues prior to implant. In six cases positive culture results were observed. Patient follow-up did not reveal any adverse effects. Although some other possibilities should be stated, contamination of heart valves during storage in liquid nitrogen should be considered as a risk element in tissue banking. Strategies to asses and prevent microbial transmission from liquid nitrogen to heart valve banking ought to be further developed.

Microbial contamination of BM products before and after processing: a report of incidence and immediate adverse events in 257 grafts

BACKGROUND

The incidence and potential clinical consequences of bacterial contamination of autologous and allogeneic BM products remains open to question. We report our experience of bacterial contamination of BM grafts and adverse events that occurred after transplantation.

METHODS

From January 2003 to February 2006, 257 BM harvests were processed and infused at our institution. Analysis of microbial contamination incidence before and after processing, sensitivity spectra of isolated bacteria and adverse events after graft infusion were analyzed.

RESULTS

Nineteen of 257 BM (7.4%) were contaminated. Coagulase-negative Staphylococcus (n=9) and Propionibacterium acnes (n=6) were the most frequently isolated microorganisms. Two of nine coagulase-negative staphylococci were found to be resistant to erythromycin and two of six P. acnes to fosfomycin and gentamycin. The frequency and severity of immediate adverse events reported in patients receiving a contaminated graft were similar to those observed in patients receiving a non-contaminated product. No major adverse sequelae occurred after infusion of contaminated grafts. Finally, none of the patients transplanted with a contaminated graft developed bacteriemia that could have been related to the isolated microorganism.

DISCUSSION

Microbial contamination of BM progenitor cell grafts does not induce severe clinical complications or infectious diseases after infusion. The vast majority of isolated pathogens were skin contaminants.

Similar Outcomes of Cryopreserved Allogeneic Peripheral Stem Cell Transplants (PBSCT) Compared to Fresh Allografts

The BMT program at Princess Margaret Hospital performed 105 transplants using cryopreserved peripheral blood stem cells (PBSC) from related allogeneic donors. The outcomes were compared with those of a historic control of 106 patients transplanted with freshly procured PBSC. The infusions were tolerated with limited toxicity related to nausea/vomiting or bradycardia, correlated with the total amount of DMSO infused. The average viability of the total nucleated cell (TNC) population after thawing was 71%. The survival of clonogenic progenitors amounted to 75% for colony-forming unit-granulocyte-macrophage (CFU-GM), 69% for burst-forming units erythroid (BFU-E), and 78% for colony-forming units granulocyte-erythrocyte-monocyte-megakaryocyte (CFU-GEMM). In contrast, colony-forming units megakaryocyte (CFU-MEG) was significantly more cryosensitive with recovery rates of 39%. The number of viable CD34(+) cells transplanted was correlated with the number of transplanted viable CFU-GM (P < .001), BFU-E (P < .001), CFU-MEG (P < .001), and CFU-GEMM (P = .049), but not with the TNC dose. The number of transplanted CD34(+) cells was correlated with engraftment of neutrophils (P = .012) and platelets (P = .013). The outcomes of cryopreseved or fresh PBSC transplants (PBSCT) with respect to engraftment of neutrophils (P = .178) and platelets (P = .785), lymphocyte recovery (P = .926), acute (P = .113), and chronic graft-versus-host disease (P = .673), recurrence (P = .295), nonrelapse mortality (P = .340), and overall survival (P = .668) were not significantly different. It is therefore reasonable to consider the option of cryopreserved allografts.

Microbial contamination of hematopoietic progenitor cell products: clinical outcome

We reviewed the results of routine microbiological assays of 3078 infused hematopoietic progenitor cell (HPC) products for autologous and allogeneic transplantation between January 2001 and December 2005. Thirty-seven (1.2%) contaminated products were found. All patients receiving contaminated infusions received empirical antibiotic prophylaxis according to the assay result. None of these patients developed a positive blood culture with the same agent, developed infections that could be attributable to the contaminated product or experienced any clinical sequelae. Coagulase-negative Staphylococcus was found in 32 (86.5%) products. Admission lengths and time to engraftment were within the expected time frame for autologous and allogeneic transplants. Microbial contamination of HPC products occurs at a low frequency; prophylactic use of antibiotics based on the microbiological assay appears to be effective in preventing clinical complications.

Cryopreservation of hematopoietic stem cells

Stem cell transplantation represents a critical approach for the treatment of many malignant and non-malignant diseases. The foundation for these approaches is the ability to cryopreserve marrow cells for future use. This technique is routinely employed in all autologous settings and is critical for cord blood transplantation. A variety of cryopreservatives have been used with multiple freezing and thawing techniques as outlined in the later chapters. Freezing efficiency has been proven repeatedly and the ability of long-term stored marrow to repopulate has been established. Standard approaches outlined here are used in many labs as the field continues to evolve.

Sterility testing of hematopoietic progenitor cell products: a single-institution series of culture-positive rates and successful infusion of culture-positive products

BACKGROUND

Administration of culture-positive hematopoietic progenitor cells (HPCs) causing adverse events has been a hypothesized yet largely unmeasured risk of the clinical practice of HPC transplantation. To enhance patient safety, the FDA has issued regulations prohibiting the use of culture-positive HPCs. Numerous studies have reported the infusion of culture-positive HPCs; however, the low frequency of adverse events prevents accurate determination of this risk.

STUDY DESIGN AND METHODS

Product culture results and clinical outcomes from January 1998 through March 2006 representing 7233 HPC collections for 2118 transplants at a single institution were reviewed.

RESULTS

A total of 119 units of HPCs (1.6%) intended for 95 patients were culture-positive. Of the 69 patients transplanted with culture-positive HPCs, 5 received products with cultures pending, and 64 received products with the positive culture results known. One of 69 patients had a new positive blood culture 5 days after infusion with the same species as the product. There was not a clinically relevant difference in the rate of infusion-related symptoms reported for patients who received culture-positive products compared to all infusions. The survival of patients who received culture-positive products (n = 69) was not different from all HPC recipients (n = 2046; p = 0.419).

CONCLUSION

No infusion-related risks of culture-positive HPCs to patient safety were identified. Our data suggest that the decision to use culture-positive HPCs must be made in the context of the global risks associated with transplants such as remobilization, replacement product availability, and the nature of the organism.

Applications of real-time PCR in the screening of platelet concentrates for bacterial contamination

Although there have been major improvements over the past few decades in detection methods for blood-borne infectious agents, platelet concentrates are still responsible for most cases of transfusion-transmitted bacterial infections. To date, real-time PCR is an indispensable tool in diagnostic laboratories to detect pathogens in a variety of biological samples. In this article, the applications of this powerful technique in the screening of platelet concentrates for bacterial contamination are discussed. Next to pathogen-specific (real-time) PCR assays, particular attention is directed to the recently developed 16S rDNA real-time PCR. This assay has been proven as a convenient way to detect bacterial contamination of platelet concentrates. The assay is sensitive and enables rapid detection of low initial numbers of bacteria in platelet concentrates. The short turnaround time of this assay allows high-throughput screening and reduction of the risk of transfusion of bacterially contaminated units. As with every method, real-time PCR has its advantages and disadvantages. These and especially limitations inherent to generation of false-positive or -negative results are emphasized. The universal nature of detection of the assay may be suitable for generalized bacterial screening of other blood components, such as red blood cells and plasma. Therefore, it is necessary to adapt and optimize detection in red blood cells and plasma with real-time PCR. Further sophistication, miniaturization and standardization of extraction and amplification methods should improve the total performance and robustness of the assay. Hence, real-time PCR is an attractive method in development as a more rapid screening test than currently used culture methods to detect bacterial contamination in blood components.

Sterility testing of cell therapy products: parallel comparison of automated methods with a CFR-compliant method

BACKGROUND

Automated blood culture systems are not FDA-approved for sterility testing of human cells, tissues, or cellular- or tissue-based products. It was previously demonstrated that BacT/ALERT (bioMérieux) and Bactec (Becton Dickinson) were superior to the manual CFR method described in the general biologics regulations, in rates of detection and time to detection of organisms seeded into mock mononuclear cell products with a variety of background media and antibiotics. In this study, the two automated systems were compared to the CFR method for sterility testing of actual cell therapy products manufactured in our facility.

STUDY DESIGN AND METHODS

Over a 36-month period, in-process and final product samples from all cell therapy products manufactured in our facility were tested for sterility both by the CFR method and by either BacT/ALERT or Bactec. Products were categorized according to collection and processing variables for analysis of results.

RESULTS

For 1617 samples of a broad range of cell therapy products, rates of true-positive tests were comparable for the automated and CFR methods (2.3% vs. 2.1%), but the CFR method had higher rates of false-positive results (7.3% vs. 0.2%). For automated systems, time to detection of organisms was equivalent to, or faster than, the CFR method.

CONCLUSION

Compared to the CFR method, both BacT/ALERT and Bactec are more sensitive, faster in time to detection, less prone to false-positive results, and less labor-intensive. Both of these automated systems are suitable for sterility testing of cell therapy products after site-specific validation has been performed.

Influence of harvest bacterial contamination on autologous peripheral blood progenitor cells post-transplant

Microbiological contamination of manipulated blood products, including hematopoietic progenitors obtained from peripheral blood, is an infrequent but persistent problem in transplant units. The relevance of such contamination in causing patient infection has been reported as insignificant, but the effect on the post-transplant course has not been well documented. We studied the incidence of bacterial contamination in autologous peripheral blood progenitor cell transplants in two of the bench processing steps, as well as the repercussions in the post-transplant course affecting incidence of infections, transfusion requirements and time to engraftment. A total of 365 aphereses performed on 152 patients were cryopreserved in 617 bags. In 31 of these bags (5.0%), bacterial cultures were positive for Coagulase-negative Staphylococcus (31.1%), S. epidermidis (21.9%), Corynebacterium sp. (6.3%), S. warneri (6.3%), Stenotrophomonas maltophilia (6.3%), Streptococcus sp. (9.4%), Viridans group Streptococcus (3.1%) and more than one bacteria (Coagulase-negative Staphylococcus plus Corynebacterium) (15.6%). Half of the bags were contaminated at the time of freezing and the others at the time of thawing. The 31 contaminated bags were infused into 17 patients. In five of these the same contaminating bacteria was found. No difference between the two groups of patients (contaminated and non-contaminated) was found on the day the fever started, length of fever, blood transfusion requirements and engraftment, but length of hospitalization was significantly greater in patients receiving contaminated transplants.

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.

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.

Safety control of peripheral blood progenitor cell processing—Eight year-survey of microbiological contamination and bag ruptures in a single institution

BACKGROUND AND OBJECTIVES

Recipients of peripheral blood progenitor cells (PBPC) are prone to opportunistic infections and their lives depend upon the availability of PBPC. Centres responsible for PBPC processing are committed to provide patients with products which are as safe as possible. These must be processed under quality assurance requirements.

MATERIALS AND METHODS

A retrospective analysis of PBPC processed in a single centre according to quality assurance premises was carried out to define the rate and the cause of microbiologic contamination and bag ruptures.

RESULTS

940 microbiologic cultures were run on 725 cryopreserved bags. Five bacterial strains were identified in the positive cultures. The rate of bacterial contamination was 1.85% of the patients, 0.34% of the collected bags, and 0.79% of the reinfused bags. Bag ruptures occurred in 1.06% of the thawed bags.

CONCLUSIONS

Permanent quality control of peripheral progenitor cell processing is mandatory. Preventive measures such as ex vivo cell manipulation in a clean room facility and the use of a double-bagged technique are highly recommended to prevent bacterial contamination and to rescue progenitor cells in the case of a bag rupture if those cells are necessary for the haematopoietic reconstitution of a patient.

Microbial contamination of hematopoietic progenitor cell grafts-incidence, clinical outcome, and cost-effectiveness: an analysis of 735 grafts

BACKGROUND

Screening of progenitor cell grafts (marrow, peripheral blood, and cord blood) for microbial contamination is required by the standards of AABB. Clinical sequelae from infusion of these contaminated grafts, however, is uncommon.

STUDY DESIGN AND METHODS

A retrospective analysis of 735 consecutive marrow and peripheral blood progenitor cell harvests between 1998 and 2003 was performed. Analysis included incidence, clinical outcome, and cost outcomes of positive blood cultures and antibiotic therapy.

RESULTS

Thirty-three of 735 (4.5%) harvests were contaminated. The incidence of microbial contamination varied with the source of the graft (4 of 26 [15%] were cord blood, 8 of 177 [4.5%] were marrow, and 21 of 532 [3.9%] were peripheral blood). Coagulase-negative Staphylococcus (n=22) and Propionibacterium acnes (n=8) were most frequently isolated. Potentially pathogenic organisms were isolated in 6 of 735 (0.81%) grafts (methicillin-sensitive Staphylococcus aureus, 4; methicillin-resistant S. aureus, 1; and Enterobacter cloacae, 1). The estimated total cost of surveillance was approximately $81,585. The cost of vancomycin therapy in 4 patients who received prophylactic antibiotic therapy was approximately $10,000. No adverse sequelae followed infusion of contaminated grafts.

CONCLUSION

Clinical sequelae following infusion of microbially contaminated progenitor cells is extremely rare. Prophylactic empiric antibiotics may be unnecessary. Routine microbial surveillance of progenitor cell grafts is a low-yield procedure.

Comparison of automated culture systems with a CFR/USP-compliant method for sterility testing of cell-therapy products

BACKGROUND

Although widely used, commercially available automated culture methods are not US Food and Drug Administration-approved for sterility testing of cell-therapy products. For cell-therapy products regulated under Section 351 of the Public Health Service Act, sterility testing must be performed by the methods described in 21 CFR 610.12 and USP <71> (CFR/USP method), or by methods demonstrated to be equivalent.

METHODS

Two automated methods, BacT/Alert (BTA; bioMerieux) and Bactec (Becton Dickinson), were compared with the CFR/USP method. Representative mononuclear cell (MNC) products were formulated using six different product media. MNC product aliquots containing 10-50 x 10(6) cells in a 0.5 mL volume were seeded with organisms, and cultured for 14 days in aerobic and anaerobic bottles of each system. Ten different organisms at target concentrations of 10 and 50 colony-forming units (CFU) per bottle were tested.

RESULTS

Positives were detected in a mean (range) of 72% (7-100%) of cultures for CFR/USP, 82% (0-100%) for BTA, and 93% (57-100%) for Bactec. For nine of the 10 organisms tested, overall detection rates for BTA and Bactec were equivalent to or higher than CFR/USP. Of the six product media tested, detection of organisms was impaired only by the medium containing multiple antibiotics: this occurred in all three systems. Both BTA and Bactec had shorter times to detection than the CFR/USP method, with overall means (ranges) of 87 (24-264) h for CFR/USP, 24 (12-54) h for BTA, and 33 (12-80) h for Bactec. Detection occurred consistently within 7 days for both BTA and Bactec, but not for CFR/USP.

DISCUSSION

Both BTA and Bactec are superior to the CFR/USP method for overall detection and time to detection of organisms in MNC products suspended in commonly used media. These data support general use of either BTA or Bactec for sterility testing of a variety of cell-therapy products, and suggest that a 7-day culture period is sufficient to detect clinically relevant organisms. These results confirm the need for bacteriostasis and fungistasis testing of antibiotic-containing products, even when antibiotic-binding substances are used.

Bacterial contamination of ex vivo processed PBPC products under clean room conditions

BACKGROUND

Patients undergoing high-dose radio- and/or chemotherapy and autologous or allogeneic PBPC transplantation are at high risk for infections owing to profound immunosuppression. In this study, the rate of microbial contamination of ex vivo processed PBPC products was analyzed, comparing preparation under clean room conditions to standard laboratory conditions.

STUDY DESIGN AND METHODS

After implementation of good manufacturing practice conditions in the two participating institutions, the microbial contamination rate of 366 PBPC harvests from 198 patients was determined under certified clean room conditions (Group A) from 2000 until 2002. To investigate influence of improved environmental conditions along with other parameters, this set of samples was compared with a historical control set of 1413 PBPC products, which have been processed ex vivo under a clean bench in a regular laboratory room and were harvested from 626 patients (Group B) from 1989 until 2000.

RESULTS

In Group B microbial contamination was found in 74 PBPC products (5.2%) from 57 patients. In Group A microbial growth was detected in 3 leukapheresis products (0.8%) from 3 patients. After exclusion of PBPC products, which were probably contaminated before manipulation, statistical analysis showed a significant difference (chi2= 10.339; p < 0.001).

CONCLUSION

These data suggest an impact of clean room conditions on the bacterial contamination rate of PBPC products. To identify confounding variables, variables like technique of leukapheresis, culture methodology, and microbial colonization of central venous catheters were taken into account. Further variables might be identified in following studies.

Endogenous microbial contamination of cultured autologous preparations in trials of cancer immunotherapy

BACKGROUND

Standardization of the manufacturing and processing of cellular immunotherapy products is necessary to ensure patient safety, establish efficacy, and demonstrate potency. Recognition of the autologous donor as a likely source of microbial contamination of cellular immunotherapy products may improve patient care and reduce expense to the laboratory.

METHODS

Data on 243 immunotherapy products manufactured in the authors' institution between December 1997 and June 2001 were retrospectively reviewed. Also reviewed were the case reports of four patients whose autologous immunotherapy products were contaminated.

RESULTS

Twenty-five (10%) of the 243 immunotherapy products processed were positive on one or more tests for microbial contamination. In six (24%) of the products, the source of microbial contamination was the autologous donor. In 17 of the remaining 19 products, test results were judged to be false-positive.

DISCUSSION

The unique processing techniques and stringent controls involved in the manufacture of cellular immunotherapy products may result in changes in the sources of microbial contamination routinely encountered. The identification of the autologous donor as a potential source of the microbial contamination of the product may assist the clinician and the laboratory in troubleshooting products with positive results on microbial sterility testing. Also, the number of false-positive results in this study indicates that further research is needed to maximize the specificity of testing while maintaining the present high sensitivity.

Catastrophic failures of freezing bags for cellular therapy products: description, cause, and consequences

BACKGROUND

Container integrity is critical for maintaining sterility of cryopreserved cellular therapy products. We investigated a series of catastrophic bag failures, first noticed in early 2001.

METHODS

Process records were reviewed for all PBPC and lymphocyte products cryopreserved in bags from January 2000 through April 2002. Patient charts were also reviewed.

RESULTS

One thousand two hundred and four bags were removed from storage for infusion to 261 patients. All products had been cryopreserved in Cryocyte poly(ethylene co-vinyl acetate) (EVA) bags in either 10% DMSO or 5% DMSO and 6% pentastarch. Product volumes were 25-75 mL, and bags were stored with overwrap bags in a liquid nitrogen tank. From January 2000 to April 2001, failure occurred in 10 of 599 (1.7%) bags. From May 2001 to April 2002, 58 of 605 (9.6%) bags failed, typically with extensive fractures that were visible before thaw. Of the 58 that failed, 24 were salvaged by aseptic methods and infused to patients under antibiotic coverage; 10 of those 24 (42%) had positive bacterial cultures. Bag failures were not related to product type, cryoprotectant solution, liquid versus vapor storage, or freezer location. Failures were linked to use of four Cryocyte bag lots manufactured in 2000 and 2001. After replacing these lots with a 1999 Cryocyte lot and with KryoSafe polyfluoroethylene polyfluoropropylene (FEP) bags, no more failures occurred in 75 and 102 bags, respectively, thawed through April 2002.

DISCUSSION

High rates of bag failure were associated with four Cryocyte bag lots. No serious adverse patient effects occurred, but bag failures led to microbial contamination, increased product preparation time, increased antibiotic use, and increased resource expenditure to replace products.

Favorable outcome after infusion of coagulase-negative staphylococci-contaminated peripheral blood hematopoietic cells for autologous transplantation

Bacterial contamination of peripheral blood hematopoietic cells collected for autologous bone marrow transplantation occurs sporadically. Although transfusion of contaminated hematopoietic cells without adverse clinical sequelae has been reported, detailed guidelines for transfusing cells with contamination are not available. We report a case of autologous hematopoietic cell transplantation that necessitated using multiple aliquots of peripheral blood hematopoietic cells known to be contaminated with coagulase-negative Staphylococcus bacteria. Prophylactic intravenous antibiotic therapy was given with the infusion of contaminated hematopoietic cells. The patient had positive results on a blood culture, but engraftment was successful, and serious adverse effects did not occur. With appropriate microbial identification and prophylactic antibiotic therapy, contaminated hematopoietic products can be safely infused when necessary with a good clinical outcome.

Processing of peripheral blood progenitor cell components in improved clean areas does not reduce the rate of microbial contamination

BACKGROUND

Microbial contamination of peripheral blood progenitor cell components (PBPCs) may cause severe complications in immunosuppressed recipients. Therefore, principles of Good Manufacturing Practice (GMP) are applicable for processing of PBPC components to reduce potential risks of contamination.

STUDY DESIGN AND METHODS

It was investigated in a retrospective study whether the microbial contamination of PBPC components could be reduced after processing in improved clean areas according to the "Manufacture of Sterile Medicinal Products." Starting in 1994, a total of 1478 autologous and allogeneic PBPC components have been collected and processed into 3149 cryopreservation bags at the Department of Transfusion Medicine. Sterility testing was performed for all bags. Until December 1998, 783 PBPC components were processed at a clean bench only (group I). Thereafter, 695 PBPC components have been processed at a clean bench located in a clean area with an airlock system for personnel and equipment (group II).

RESULTS

In group I, 16 of 1555 bags (1.03%) showed positive results in the first sterility testing. In group II, 21 of 1594 bags (1.32%) were positive (p = NS). The clinical follow-up was inconspicuous.

CONCLUSION

Microbial contamination of PBPC components could not be reduced by installation of improved clean area conditions.