Microbial Contamination of Hematopoietic Stem Cell Products: Incidence and Clinical Sequelae

Development of an in-house bone marrow collection kit: The Catalan bone marrow transplantation group experience

BACKGROUND AND OBJECTIVES

Bone marrow (BM) harvesting is one of the essential sources of stem cells for haematopoietic stem cell transplantation. In 2019, commercial BM collection kits became unavailable in Europe. Consequently, we created an in-house BM collection kit as an alternative.

MATERIALS AND METHODS

We compared two groups of BM collections. The first collections were taken using an in-house kit from June 2022 through February 2023 and the second with a commercial kit from February 2021 through May 2022. These all took place at seven collection centres (CC). We analysed the harvest quality (cell blood count, CD34+ cells, viability, potency and sterility), the incidents occurring with each kit and the time to neutrophil and platelet engraftment in recipients.

RESULTS

A total of 23 donors underwent BM harvesting with the in-house kit and 23 with the commercial one. Both cohorts were comparable regarding donor characteristics, CC and time to procedure. No statistical differences were found in harvest quality between the in-house and commercial kits. A new transfusion set was required in three BM harvests (13%) with the in-house kit because of filter clogging. The median time to neutrophil and platelet engraftment was 21 days for both cohorts and 29 days (in-house) and 33 days (commercial), p = 0.284, respectively.

CONCLUSION

The in-house BM collection kit offers a real approach to solve the diminished supply of commercial kits. A higher risk of filter clogging was observed compared with commercial kits due to the lack of 850 and 500 μm filters.

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.

Sterility Testing for Hematopoietic Stem Cells

Over the last two decades, rapid technological advances have led to the wide adoption of cell and gene therapy products for the treatment of a variety of disease states. In this study, we reviewed the literature between 2003 and 2021 to provide a summary of overarching trends associated with microbial contamination in hematopoietic stem cells (HSCs) derived from peripheral blood, bone marrow, and cord blood. We provide a brief background on the regulatory context for human cells, tissues, and cellular and tissue-based products (HCT/Ps) as regulated by the US Food and Drug Administration (FDA), sterility testing expectations for autologous (Section 361) and allogeneic (Section 351) HSC products, and discuss clinical risks associated with the infusion of a contaminated HSC product. Finally, we discuss the expectations for current good tissue practices (cGTP) and current good manufacturing practices (cGMP) for the manufacturing and testing of HSC based on Section 361 and Section 351 categorization, respectively. We provide commentary on what is practiced in the field and discuss the critical need for updates to professional standards that keep pace with advancing technologies with an aim to clarify expectations for manufacturing and testing facilities to improve standardization across institutions.

The ratio of nicotinic acid to nicotinamide as a microbial biomarker for assessing cell therapy product sterility

Controlling microbial risks in cell therapy products (CTPs) is important for product safety. Here, we identified the nicotinic acid (NA) to nicotinamide (NAM) ratio as a biomarker that detects a broad spectrum of microbial contaminants in cell cultures. We separately added six different bacterial species into mesenchymal stromal cell and T cell culture and found that NA was uniquely present in these bacteria-contaminated CTPs due to the conversion from NAM by microbial nicotinamidases, which mammals lack. In cells inoculated with 1 × 10⁴ CFUs/mL of different microorganisms, including USP <71> defined organisms, the increase in NA to NAM ratio ranged from 72 to 15,000 times higher than the uncontaminated controls after 24 h. Importantly, only live microorganisms caused increases in this ratio. In cells inoculated with 18 CFUs/mL of Escherichia coli, 20 CFUs/mL of Bacillus subtilis, and 10 CFUs/mL of Candida albicans, significant increase of NA to NAM ratio was detected using LC-MS after 18.5, 12.5, and 24.5 h, respectively. In contrast, compendial sterility test required >24 h to detect the same amount of these three organisms. In conclusion, the NA to NAM ratio is a useful biomarker for detection of early-stage microbial contaminations in CTPs.

Autologous hematopoietic stem cell product contaminated with Salmonella due to occult salmonellosis in an asymptomatic donor

Recent advancements in infectious disease testing methods and pathogen reduction technologies have greatly reduced the incidence of microbial contamination of allogeneic blood products. Despite this significant reduction, contamination of autologous cellular therapy products remains a challenging issue, as many of these mitigation strategies are not feasible for such products. Most microorganisms isolated from cellular therapy products are Gram-positive normal skin flora, and studies have demonstrated that adverse effects are infrequent when these contaminated products are infused. However, no prior report has documented an autologous hematopoietic stem cell (HSC) or other cellular therapy product contaminated with Salmonella bacteria-a pathogenic Gram-negative organism. We present the first known case of Salmonella contaminating an HSC product secondary to occult salmonellosis in the donor, and discuss the implications of this contaminating organism and the therapeutic dilemma posed by this scenario.

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.

Transfusion support for stem cell transplant recipients

Hematopoietic stem cell patients regularly require transfusion support. Indications for transfusion in this population are similar to other patients being treated with chemoradiation; however, special considerations must be made in regards to pretransfusion testing, ABO compatibility, product modifications, and anticipated challenges while patients undergo engraftment. Additionally, infusion of hematopoietic stem cells requires acute understanding of product collection, modification, and potential side effects. As these patients often require numerous platelet transfusions, platelet refractoriness may be encountered and practice options are discussed. We review current indications and guidelines for transfusion in hematopoietic stem cell patients and make recommendations for best practice based on current literature.

Sterility Testing for Cellular Therapies: What Is the Role of the Clinical Microbiology Laboratory?

Sterility testing of cellular therapy products along with the associated environmental monitoring requirements for aseptic facilities, including compounding pharmacies, continues to impact clinical microbiology laboratories, as evidenced by the numerous discussions recurring on American Society for Microbiology Division C and ClinMicroNet listservs. This minireview provides an overview of this complex field of current good manufacturing practices (cGMP) based on biopharmaceutical industry standards and summarizes the compendial and alternative rapid microbial test methods available for product sterility and Mycoplasma testing. In addition, this minireview highlights major overarching regulatory requirements governing any laboratory performing product testing as regulated by the United States Food and Drug Administration (FDA). These requirements are different from the more familiar clinical requirements of the Clinical Laboratory Improvement Act of 1988 (CLIA '88), the College of American Pathologists (CAP), and the Joint Commission on Accreditation of Healthcare Organizations (JCAHO), all of which have no jurisdiction in this area. As the cellular therapy field continues to advance and an increasing number of medical centers participate in clinical trials of these novel therapies, it is critical that laboratories have a sound understanding of the major regulations and cGMP practices governing microbiological testing in the biopharmaceutical industry.

Bacterial contamination rates in extracorporeal photopheresis

BACKGROUND

Extracorporeal photopheresis (ECP) is an immunosuppressive treatment that involves leukocyte apheresis, psoralen and UV light treatment, and subsequent reinfusion. Patients treated with ECP are usually immunosuppressed. Bacterial contamination therefore poses a much unwanted risk, but incidence data are lacking.

PATIENTS AND METHODS

We screened all 1922 consecutive ECP procedures scheduled within a roughly 3-year period for eligibility. Those with missing data on ECP method (inline or offline) or type of venous access (peripheral or central) were excluded. ECPs with complete aerobic and anaerobic microbial testing of baseline patient blood samples (n = 1637) and of ECP cell concentrates (n = 1814) were included in the analysis.

RESULTS

A test for microbial contamination was positive for 1.82% of the cell concentrates, with central venous access was the most significant risk factor for the contamination (odds ratio = 19). Patient blood samples were positive in 3.85% of cases, but no patients became septic. Staphylococcus spp. were most abundant, and products with bacterial contamination did not cause side effects after reinfusion. There were no significant differences in contamination rates between inline and offline ECP.

CONCLUSION

These findings stress the importance of sterile procedures and the benefits of using peripheral over central venous access for reducing the risk of bacterial contamination in ECP.

Microbial contamination risk in hematopoietic stem cell products: retrospective analysis of 1996–2016 data

Quality assurance and safety of hematopoietic stem cells (HSC) with special emphasis on bacterial and fungal contamination is the prerequisite for any transplantation procedure. The aim was to determine the incidence rate of such contamination during processing of transplantation material with regard to HSC source: peripheral blood stem cell (PBSC), bone marrow (BM), or cord blood (CB). Analysis involved autologous and allogenic products dedicated for patients and comprised in all 4135 donations, including 112 BM (2.70%), 3787 PBSC (91.60%), and 236 CB (5.70%) processed in cell bank over the period 1996–2016. Aerobic and anaerobic contamination was determined.

Analysis of the 20-year data revealed 42 contaminated products: 25 PBSC (0.66% of tested units) and 17 CB (7.20% of tested units). No microbial contamination of BM products was detected. Overall percentage of contaminated products was 1.01%, mostly with Staphylococcus epidermidis (61.36%). Bacterial contamination rate at cell bank is relatively low and processing in a closed system does not seem as crucial as might be expected. This is particularly true for BM components. Equally important are evaluation of donor’s medical status and condition of the puncture site for collection of source material. Implementation of appropriate sample collection procedures should help minimize the risk of false-positive results due to environmental contamination.

Prospective Evaluation of a Practical Guideline for Managing Positive Sterility Test Results in Cell Therapy Products

Product safety assurance is crucial for the clinical use of manufactured cellular therapies. A rational approach for delivering products that fail release criteria (because of potentially false-positive sterility results) is important to avoid unwarranted wastage of highly personalized and costly therapies in critically ill patients where benefits may outweigh risk. Accurate and timely interpretation of microbial sterility assays represents a major challenge in cell therapies. We developed a systematic protocol for the assessment of positive microbial sterility test results using retrospective data from 2007 to 2016. This protocol was validated and applied prospectively between October 2016 and September 2017 to 13 products from which positive sterility results had been reported. Viable and nonviable environmental monitoring (EM) data were collected concurrently as part of a facility control assessment. Three of 13 (23%) positive sterility results were attributable to bone marrow collections that had been contaminated with skin flora during harvest; all were infused without pertinent infectious sequelae. Of the remaining 10, 1 was deemed a true positive and was discarded before infusion, whereas 9 were classified as false positives attributed to laboratory sampling and/or culturing processes. Three products deemed false positive were infused and 6 were withheld because of patient issues unrelated to microbial sterility results. No postinfusion-associated infectious complications were documented. Almost half of the positive EM findings were skin flora. Paired detection of an organism in both product and associated EM was identified in 1 case. Application of our validated protocol to positive product sterility test results allowed for systematic data compilation for regulatory evaluation and provided comprehensive information to clinical investigators to ensure timely and strategic management for product recipients.

Development of a proof of principle for universal neutralization of antibiotics in cord blood by-products used for sterility testing

BACKGROUND

Bacterial contamination of cord blood (CB) represents a safety risk for transplantation patients. CB sterility testing at Canadian Blood Services' Cord Blood Bank is performed using a 1:1 mix of CB-derived plasma and red blood cells (RBCs). Culture bottles of an automated culture system, which lack antimicrobial neutralization properties, are used for bacterial screening of CB. This process is unsuitable for CB-containing antibiotics, potentially resulting in false-negative results. This study was aimed at developing a protocol for antibiotic neutralization in CB used for sterility testing.

STUDY DESIGN AND METHODS

Phase 1: four neutralizers-penicillinase, ion exchange resins L and A, lecithin + Tween80, and activated charcoal (AC)-were individually tested to neutralize penicillin or gentamicin in cultures of Staphylococcus epidermidis or Klebsiella pneumoniae, respectively, adjusted to 100 colony forming units/mL, in Müller-Hinton broth (MHB). Phase 2: combinations of penicillinase plus resin L or penicillinase plus AC were assayed for the simultaneous neutralization of both antibiotics in MHB. Phase 3: penicillinase plus resin L was used to neutralize both antibiotics in CB sterility testing samples (plasma + RBCs).

RESULTS

Phase 1: penicillin was neutralized by penicillinase and resin A, while gentamicin was neutralized by resin L and AC. Phase 2: the antibiotics were simultaneously neutralized by the two neutralizer combinations tested. Phase 3: neutralization of both antibiotics in CB was achieved with penicillinase and resin L.

CONCLUSION

A protocol for antibiotic neutralization in CB sterility testing samples has been successfully developed at Canadian Blood Services' Cord Blood bank. This in-house assay applies to any culture-based CB bacterial screening method.

Bone marrow harvest from unrelated donors-up-to-date methodology

OBJECTIVES

Bone marrow harvesting is one of the essential sources of stem cells for hematopoietic stem cell transplantation. We describe here the current "up-to-date" standard of the bone marrow harvest in unrelated stem cell donors.

METHODS

We analyzed medical data of 187 unrelated hematopoietic stem cell donors who underwent bone marrow harvest without previous peripheral blood stem collection at the center between 2011 and 2015. The methodology of marrow collection includes multiple cells aimed at safety of the procedure, for example, educational movie, modified skin disinfection protocol, cell enumeration during the procedure, reduction of the contamination surfaces, and ongoing monitoring of the quality of work of the doctors.

RESULTS

The total nucleated cell count over 2×10⁸ per kg of recipient has been reached in 93.6% of harvests. All of the donors harvested more than 1×10⁸ per kg of the recipient. There were no donors who required transfusions or had serious adverse events during and after the harvest.

CONCLUSION

We describe here the current up-to-date standard of bone marrow harvest, which leads to excellent results in majority of donors without causing significant complications during the donation.

Optimization of cord blood unit sterility testing: impact of dilution, analysis delay, and inhibitory substances

BACKGROUND

Different methods are used by cord blood banks to prepare samples for sterility testing. Suboptimal methods can result in the release of contaminated products. In our organization, samples are prepared by diluting the final product in RPMI-1640 medium. In this work, we have compared our method with different approaches to verify whether optimization should be sought.

STUDY DESIGN AND METHODS

Cord blood units (n = 6 units per bacterial strain) characterized to contain inhibitory substances or not were inoculated (10 colony-forming units/mL) with Streptococcus agalactiae, Staphylococcus epidermidis, Klebsiella pneumoniae, Escherichia coli, or Bacteroides fragilis. After plasma and red blood cell removal, stem cell concentrates were diluted in RPMI-1640, thioglycollate, or the unit's plasma. These products, as well as final product, plasma, and red blood cell fractions, were held from 0 to 72 hours at 20 to 24°C before inoculation in culture bottles and detection using the BacT/ALERT 3D system.

RESULTS

Dilution of cell concentrates in RPMI-1640 allowed bacterial detection in 93.3% of noninhibitory cord blood samples after a 24-hour storage period. Thioglycollate medium better promoted bacterial growth in inhibitory cord blood samples that were held for 72 hours before testing (66.7%) compared with RPMI-1640 (45.0%). Less than 33% of all spiked plasma samples were detected by the BacT/ALERT 3D system.

CONCLUSION

Diluting cord blood samples in culture medium containing bacterial growth promoting substances is a suitable option for sterility testing, whereas the use of plasma should be proscribed, because it might lead to false-negative results. Because inhibitory substances affect bacterial growth, inoculation of culture bottles should be done rapidly after sample preparation.

Molecular characterization of microbial contaminants isolated from Umbilical Cord Blood Units for transplant

Disposal of Umbilical Cord Blood Units due to microbial contamination is a major problem in Cord Blood Banks worldwide as it reduces the number of units available for transplantation. Additionally, economic losses are generated as result of resources and infrastructure used to obtain such units. Umbilical Cord Blood Units that showed initial microbial contamination were subject to strains isolation, identification, and characterization by sequencing the 16S rRNA gene and Enterobacterial Repetitive Intergenic Consensus (ERIC-PCR). Moreover, tests of antimicrobial resistance/sensitivity and phenotypic activities that may play an important role in microbial infection were performed. Microbial contamination was detected in 120 Umbilical Cord Blood Units (2.31%) in the period from 2003 to 2013. The most frequently isolated strains were Enterococcus faecium, followed by Staphylococcus epidermidis, Escherichia coli, Enterococcus faecalis, Staphylococcus haemoliticus, Klebsiella pneumoniae, Enterococcus durans, Lactobacillus helveticus, Enterococcus hiriae and Roseomonas genomospecies 5. The ERIC-PCR assays revealed a wide genetic diversity in some strains although belonging to the same genus and specie, indicating different sources of contamination. Broad-spectrum penicillins, third generation cephalosporins, aminoglycosides, and fluoroquinolones showed lower inhibitory activity on the tested strains. All strains were proteolytic, 67.69% were amylase-positive, 27.6% hemolysis-positive, and 34.71% nuclease-positive. The most common sources of contamination were: vaginal flora, digestive tract, and skin flora, highlighting the need for staff training in good manufacturing practices in collection SCU since all contaminants identified are part of the microbial flora of the donors. Implications and consequences in the therapeutic use of Umbilical Cord Blood Units for transplantation contaminated by multiresistant bacteria in immunocompromised patients are discussed.

Critical care of sub-lethal irradiated transgenic mice using a complete soft food formula-DietGel76A™

The objective of this research is to determine whether the administration of a complete soft food formula to sub-lethal irradiated animals from three different transgenic mouse strains over a period of 21 consecutive days will have a significant impact on the clinical signs, and the general survival rate of the animals. Our hypothesis is that using DietGel76A™, along with an antibiotic treatment, strict handling and manipulation procedures, the general mortality rate, as well as the onset of the clinical signs between the treated animals and the control animals, will be significantly lower. This hypothesis was confirmed for the C57BL/6 mice. However, the treatment with DietGel76A™ had only a very limited impact on the recovery of more irradiation sensitive strains (CD45.1 and mostly NRG). Further studies must be conducted on mice from these strains in order to assess whether mice belonging to more sensitive strains should be on DietGel76A™ for a longer period of time (at least 42days post irradiation).

A policy for the disposal of autologous hematopoietic progenitor cells: report from an Italian consensus panel

BACKGROUND

Autologous stem cell transplantation (ASCT) requires collection and cryopreservation of hematopoietic progenitor cells (HPCs), which in turn may be partially or never reinfused. Thus, HPC storage has become a logistic, ethical, and economic issue. SIDEM, GITMO, and CNT/ISS endorsed a project aimed to define national criteria for HPC disposal aimed to guarantee appropriateness and equity.

STUDY DESIGN AND METHODS

A multidisciplinary panel was convened including HPC harvest and manipulation experts from apheresis units, hematologists with clinical expertise in ASCT, a representative of the national health authority, and a bioethicist. An analytic hierarchy process (AHP) was carried out to select disposal criteria.

RESULTS

The AHP selected two criteria for prompt disposal of freshly collected HPCs: an abnormal freezing procedure causing highly reduced viability or major microbiology contamination. Moreover, AHP selected six major criteria, each one of them allowing for the disposal of stored HPC units: patient death, withdrawal of consent to ASCT, contraindications or loss of indications to ASCT, a damaged label that prevents correct identification of the unit, and time elapsed since harvest longer than 10 years. Three minor criteria were additionally identified that allowed to anticipate disposal only provided that viability levels are below the limit of acceptance: a documented cold chain interruption, loss of bag integrity, and total amount of stored CD34+ cells lower than 1 × 10(6) /kg or lower than 2 × 10(6)/kg in patients with a successfully completed stem cell transplantation program.

CONCLUSIONS

A formal consensus process allowed SIDEM and GITMO to propose a policy for autologous HPC disposal that fulfills clinical, ethical, and economic criteria.

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 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.

Evaluation of the sterility testing process of hematopoietic stem cells at Canadian Blood Services

BACKGROUND

Sterility testing of hematopoietic stem cells (HSCs) at The Canadian Blood Services Stem Cell Laboratory is performed using BacT/ALERT aerobic (SA) culture bottles. This study was conducted to verify the efficacy of this method and to assess the use of the BacT/ALERT aerobic (BPA) and anaerobic (BPN) culture bottles for microbial testing of HSCs.

STUDY DESIGN AND METHODS

HSC products, including cryopreserved apheresis peripheral blood, marrow, and cord blood and fresh cord blood, were spiked with four aerobic organisms including Staphylococcus epidermidis, Bacillus cereus, Pseudomonas aeruginosa, and Candida albicans, and the anaerobe Bacteroides fragilis at a target concentration of 100 colony-forming units (CFUs)/mL. One to 2 mL of pre- and postspiked samples was inoculated into SA, BPA, and BPN bottles in duplicate and incubated for 5 to 10 days. The presence of the testing organisms in positive culture bottles was confirmed by plating on blood agar.

RESULTS

The BacT/ALERT system detected the aerobic organisms in all HSCs in SA and BPA bottles within 34.1 hours while B. fragilis was detected only in BPN bottles within 68.6 hours. The mean recovered concentration of microorganisms in the HSC products ranged from 55 to 352 CFUs/mL with the exception of B. cereus, which was greater than 10(3) CFUs/mL.

CONCLUSION

This study shows that the current sterility testing process at the Canadian Blood Services Stem Cell Laboratory detected the tested aerobic but not the anaerobic microbial contaminants in HSCs. The ability of the BacT/ALERT system using BPA and BPN bottles to detect bacterial contamination in HSCs was also demonstrated.

Factors affecting microbial contamination rate of cord blood collected for transplantation

BACKGROUND

Collection and processing of cord blood (CB) is associated with significant risk of microbial contamination and hence relevant standards mandate microbial screening of the final product. This study aimed to determine the contamination rate and associated risk factors during 14 years of banking at the Sydney Cord Blood Bank.

STUDY DESIGN AND METHODS

CB was collected and processed using a closed system and tested for contamination using blood culture bottles (BacT/ALERT, bioMérieux) incubated for a minimum of 5 days. Four microbial screening methods were used with different combinations of inoculated bottles (adult or pediatric) and associated sample volumes (10 or 1 mL).

RESULTS

Of 13,344 CB units screened, 537 (4.0%) tested positive for contamination, with Bacteroides spp. (20.9%), Staphylococcus spp. (18.6%), and Propionibacterium spp. (13.7%) being the most common isolates. The contamination rate reduced from 10% in 1997 to 1.1% in 2009. Multivariate analysis demonstrated the following variables were independently associated with higher contamination rates: vaginal delivery, collection by obstetric staff, and use of an anaerobic bottle in addition to an aerobic bottle (which facilitated a larger sample inoculation volume than pediatric bottles).

CONCLUSIONS

This study demonstrates that contamination rates of CB collected for transplantation can be substantially reduced by collection after cesarean delivery and utilizing trained CB collection staff. These data also indicate that the common practice of testing using a pediatric (aerobic) bottle with its attendant small volume of the final CB product may be suboptimal for sensitive detection of contaminating anaerobic microbes.

Clinical significance of positive cranial bone flap cultures and associated risk of surgical site infection after craniotomies or craniectomies

OBJECT

The risk of surgical site infection (SSI) after craniotomies or craniectomies in patients in whom contaminated bone flaps have been reimplanted has not been determined. The objectives of this study were to identify the prevalence of bone flaps with positive cultures--especially those contaminated with Propionibacterium acnes--to assess the risk of SSI after reimplanting (either during the initial operation or subsequently) bone flaps with positive cultures, and to identify risk factors for SSI following the initial craniotomies or craniectomies.

METHODS

The authors conducted a retrospective review of cases in which patients underwent craniotomy/craniectomy procedures between January and October 2007 in the neurosurgery department at the University of Iowa Hospitals and Clinics. They also reviewed processes and procedures and did pulsed field gel electrophoresis of P. acnes isolates to look for a common source of contamination. They then conducted a prospective cohort study that included all patients who underwent craniotomy/craniectomy procedures between November 2007 and November 2008 and met the study criteria. For the cohort study, the authors obtained cultures from each patient's bone flap during the craniotomy/craniectomy procedures. Data about potential risk factors were collected by circulating nurses during the procedures or by a research assistant who reviewed medical records after the procedures. An infection preventionist independently identified SSIs through routine surveillance using the Centers for Disease Control and Prevention's definitions. Univariate and bivariate analyses were performed to determine the association between SSI and potential risk factors.

RESULTS

The retrospective review did not identify specific breaks in aseptic technique or a common source of P. acnes. Three hundred seventy-three patients underwent 393 craniotomy/craniectomy procedures during the cohort study period, of which 377 procedures met the study criteria. Fifty percent of the bone flaps were contaminated by microorganisms, primarily skin flora such as P. acnes, coagulase-negative staphylococci, and Staphylococcus aureus. Reimplanting bone flaps that had positive culture results did not increase the risk of infection after the initial craniotomy/craniectomy procedures and the subsequent cranioplasty procedures (p = 0.80). Allowing the skin antiseptic to dry before the procedures (p = 0.04, OR 0.26) was associated with lower risk of SSIs. Female sex (p = 0.02, OR = 3.49) was associated with an increased risk of SSIs; Gliadel wafer implants (p = 0.001, OR = 8.38) were associated with an increased risk of SSIs after procedures to treat tumors.

CONCLUSIONS

Operative factors such as the way the skin is prepared before the incision rather than the skin flora contaminants on the bone flaps may play an important role in the pathogenesis of SSIs after craniotomy/craniectomy. Gliadel wafers significantly increased the risk of SSI after procedures to treat tumors.

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.