Clostridium infections associated with musculoskeletal-tissue allografts

Lethal toxin is a critical determinant of rapid mortality in rodent models of Clostridium sordellii endometritis

The toxigenic anaerobe Clostridium sordellii is an uncommon but highly lethal cause of human infection and toxic shock syndrome, yet few studies have addressed its pathogenetic mechanisms. To better characterize the microbial determinants of rapid death from infection both in vitro and in vivo studies were performed to compare a clinical strain of C. sordellii (DA-108), isolated from a patient who survived a disseminated infection unaccompanied by toxic shock syndrome, to a virulent reference strain (ATCC9714). Rodent models of endometrial and peritoneal infection with C. sordellii ATCC9714 were rapidly lethal, while infections with DA-108 were not. Extensive genetic and functional comparisons of virulence factor and toxin expression between these two bacterial strains yielded many similarities, with the noted exception that strain DA-108 lacked the tcsL gene, which encodes the large clostridial glucosyltransferase enzyme lethal toxin (TcsL). The targeted removal by immunoprecipitation of TcsL protected animals from death following injection of crude culture supernatants from strain ATCC9714. Injections of a monoclonal anti-TcsL IgG protected animals from death during C. sordellii ATCC9714 infection, suggesting that such an approach might improve the treatment of patients with C. sordellii-induced toxic shock syndrome.

Comparative analysis of the extracellular proteomes of two Clostridium sordellii strains exhibiting contrasting virulence

Clostridium sordellii is a toxin-producing anaerobic bacillus that causes severe infections in humans and livestock. C. sordellii infections can be accompanied by a highly lethal toxic shock syndrome (TSS). Lethal toxin (TcsL) is an important mediator of TSS. We recently obtained a clinical strain of C. sordellii (DA-108) lacking the TcsL-encoding tcsL gene, which was not fatal in rodent models of infection, in contrast to a tcsL(+) reference strain (ATCC9714). Protein preparations derived from cell-free, stationary phase cultures obtained from ATCC9714 were lethal when injected into mice, while those obtained from DA-108 were not, a difference that was attributed to the unique presence of TcsL in the ATCC9714-derived proteins. We questioned whether there were other major differences between the extracellular proteomes of these two strains, apart from TcsL. Two-dimensional gel electrophoresis was conducted using crude cell-free supernatants from these strains and 14 differentially expressed proteins were subjected to mass spectrometric analysis. Nine of these 14 proteins were more highly expressed by DA-108 and 5 by ATCC9714. Twelve of the 14 proteins isolated from the 2-D gels were putatively identified by mass spectrometry. Several of these proteins were identical, possibly reflecting enzymatic cleavage, degradation, and/or post-translational modifications. Excluding identical sequences, only 5 unique proteins were identified. Four proteins (ferredoxin-nitrite reductase; formate acetyltransferase; Translation Elongation Factor G; and purine nucleoside phosphorylase) were over-expressed by DA-108 and 1 (N-acetylmuramoyl-l-alanine amidase) by ATCC9714. These results support the concept that TcsL is the major determinant of C. sordellii TSS during infection.

Isolation and implantation of bone marrow-derived mesenchymal stem cells with fibrin micro beads to repair a critical-size bone defect in mice

Fibrin microbeads (FMBs) made using thermal treatment of fibrin drops in oil can efficiently isolate mesenchymal stem cells (MSCs) from bone marrow (BM) and other similar sources and culture them continuously in suspension culture. The pure mesenchymal profile of MSCs isolated using FMBs and their differentiation potency to different mesenchymal lineages were previously described in detail. In the current study, MSCs were isolated from the BM of (GFP+) C57/bl mice using FMBs. Addition of pro-osteogenic medium with 10 mM of ss-glycerolphosphate, 50 microg/mL of ascorbic acid, and 10(-8) M of dexamethasone for 1 month resulted in ossified bone-like solid cellular structures, as seen using fluorescence and scanning electron microscopy (SEM). Such spontaneously formed structures were implanted in full-depth approximately 5-mm-diameter drilled defects in the skulls of wild-type c57/bl mice. Two months later, the excised upper parts of the skulls with the defects were viewed using fluorescence microscopy for green fluorescence protein of the cells in the defect and using SEM. They were also scanned using micro-computed tomography to visualize the formation of new hard tissue. Then the samples were processed and sectioned for hematoxylin and eosin staining and immunohistochemistry. Implanted FMBs loaded with (GFP+) MSCs formed partially mature, dense bone-like tissue using a residual moderate inflammatory process containing remnants of FMBs and neo-angiogenesis. The filled defect with bone-like tissue had a Ca/P ratio similar to that of native bone. Limited merging of the implant with the skull indicated that the induced bone regeneration derived from the MSCs that were delivered with the implant. No repair was seen in the control animals without implants or where the defect was filled with FMBs only. Repair scoring (on a 0-5 scale) was found to be 3.38+/-0.35 in the experimental arm, relative to 0 in the controls (p < 0.001).

Bioburden assessment of banked bone used for allografts

Allograft bone is commonly used in reconstructive orthopaedic surgery and needs to be assessed for bioburden before transplant. The Microbiology Department of the South Eastern Area Laboratory Services (SEALS), located at the St. George Hospital, Sydney, has provided this service to the New South Wales (NSW) Bone Bank. This study reviewed the organisms isolated from femoral head allografts of living donors from the NSW Bone Bank over a 7-year period. It was found that growth was reported from 4.9% of samples with the predominant organism being coagulase-negative staphylococci. This review will focus on the micro-organisms isolated, the interaction of the laboratory with the bone bank, the relevance of the bioburden assessment in the overall quality process and patient safety.

Tissue Engineering Options for Ligament Healing

The anterior cruciate ligament (ACL) is one of five ligaments in the knee that are important for stability and kinematics. It is also the most commonly injured ligament of the knee and due to its poor healing potential, severe damage warrants surgical intervention including complete replacement. Ligaments are longitudinally arranged, complex tissues; the mechanical properties of ligaments are a direct result of their components and the arrangement of these components in the tissue. It is these mechanics that have made ligaments so difficult to replace. Past ACL replacements have had many limitations that prevented their extensive use. These limitations range from mechanical fatigue over time to fraying of the device after implantation. In light of these problems, investigators have begun to pursue a host of new techniques to create a range of viable options for the repair, replacement, and/or regeneration of the ACL. These options include tissue engineered scaffolds with novel designs and specially treated transplanted tissues. In this article, the composition, arrangement, and mechanics of the ACL will be discussed in order to elucidate important aspects of ACL repair; past replacements will also be discussed. Afterwards, novel replacement options that look to solve problems faced by older replacement options will be presented. These devices use a wide variety of materials and designs to replicate ligament mechanics and allow for new tissue regeneration.

Tissue processing: role of secondary sterilization techniques

Secondary sterilization of musculoskeletal allografts may use chemicals, radiation, or combinations of these. No sterilization techniques have been definitively proven to be more effective than others, and their biomechanical and biological effects on allograft tissue remain largely unknown. The current risk of an allograft infection appears to be much less than the risk of infection surrounding the surgical procedure itself. With appropriate donor screening, improved donor testing—including nucleic acid testing (NAT), and adherence to AATB standards—the risk of disease transmission or infections can be eliminated or substantially decreased.

Primary ACL reconstruction using allograft tissue

While bone-patellar tendon-bone (BPTB) autograft continues to be the "gold standard" and most popular graft choice for primary anterior cruciate ligament (ACL) reconstructions, the use of allograft tissues in ACL reconstruction has steadily increased over the last 2 decades. Advantages of allograft include a lack of donor-site morbidity, unlimited available sizes, shorter operative times, availability of larger grafts, smaller incisions, improved cosmesis, lower incidence of postoperative arthrofibrosis, faster immediate postoperative recovery, and less postoperative pain. Disadvantages include the potential for disease transmission and prolonged graft healing. Presented in this article are 2 techniques used at the authors' institution for primary ACL reconstruction with allograft. With the proper indications, knowledge of graft preparation and handling, and technique, allograft tissues in ACL reconstructions can provide the surgeon with clinical results equal to those of autograft reconstructions.

Evaluation of Gram-positive rod surveillance for early anthrax detection

Since 2003, Connecticut laboratories have reported Gram-positive rod (GPR) isolates detected within 32 h of inoculation from blood or cerebrospinal fluid. The objectives were to rapidly identify inhalational anthrax and unusual Clostridium spp. infections, and to establish round-the-clock laboratory reporting of potential indicators of bioterrorism. From 2003 to 2006, Connecticut's GPR surveillance system identified 1134 isolates, including 657 Bacillus spp. (none B. anthracis) and 241 Clostridium spp. Reporting completeness and timeliness improved to 93% and 92%, respectively. Baseline rates of Bacillus spp., Clostridium spp. and other GPR findings have been established and are stable. Thus far, no cases of anthrax and no unusual clusters of Clostridium spp. have been detected by the GPR surveillance system. This system would probably have confirmed the inhalational anthrax case in Pennsylvania in 2006 3 days sooner than traditional reporting. Using audits and ongoing evaluation, the system has evolved into a highly functional 24/7 laboratory telephone reporting system with almost complete reporting.

Stem cell and cellular therapy developments

Recent discoveries on human and non-human stem cells have prompted the development of several studies aimed at the translation of laboratory evidences into novel clinical procedures collectively known as 'cellular therapy'. In this regard, a number of features specifically related to the clinical setting require stringent evaluation, including, but not limited to: ethical appropriateness; donor and recipient informed consent; autologous versus allogeneic use; media and devices for cell collection, processing, characterization, storage and distribution; donor and recipient adverse events registration and management; risk-to-benefit and cost analysis; outcome analysis; production sites accreditation and management; regulatory oversight. This article describes recent national and international developments related to the distribution of cells and tissues for clinical use. Moreover, an example is reported of the implementation of a cellular therapy production site compliant with good manufacturing practices (GMPs) in a large European University hospital.

Organ and tissue safety workshop 2007: advances and challenges

A workshop in June 2005 ("Preventing Organ and Tissue Allograft-Transmitted Infection: Priorities for Public Health Intervention") identified gaps in organ and tissue safety in the US. Participants developed a series of allograft safety initiatives. "The Organ and Tissue Safety Workshop 2007: Advances and Challenges" assessed progress and identified priorities for future interventions. Awareness of the challenges of allograft-associated disease transmission has increased. The Transplantation Transmission Sentinel Network will enhance communication surrounding allograft-associated disease transmission. Other patient safety initiatives have focused on adverse event reporting and microbiologic screening technologies. Despite progress, improved recognition and prevention of donor-derived transmission events is needed. This requires systems integration across the organ and tissue transplantation communities including organ procurement organizations, eye and tissue banks, and transplant infectious disease experts. Commitment of resources and improved coordination of efforts are required to develop essential tools to enhance safety for allograft recipients.

Musculoskeletal allograft risks and recalls in the United States

There have been several improvements to the US tissue banking industry over the past decade. Tissue banks had limited active government regulation until 1993, at which time the US Food and Drug Administration began regulatory oversight because of reports of disease transmission from allograft tissues. Reports in recent years of disease transmission associated with the use of allografts have further raised concerns about the safety of such implants. A retrospective review of allograft recall data was performed to analyze allograft recall by tissue type, reason, and year during the period from January 1994 to June 30, 2007. During the study period, more than 96.5% of all allograft tissues recalled were musculoskeletal. The reasons underlying recent musculoskeletal tissue recalls include insufficient or improper donor evaluation, contamination, recipient infection, and positive serologic tests. Infectious disease transmission following allograft implantation may occur if potential donors are not adequately evaluated or screened serologically during the prerecovery phase and if the implant is not sterilized before implantation.

Allograft and bone morphogenetic proteins: an overview

Allograft is frequently used in orthopaedic and trauma surgery. On top of safety issues its biological activity is limited also due to processing. Consequently, the combination of allograft with osteoinductive substances may increase its effectiveness and decrease failure rates. In particular Bone Morphogenetic Proteins (BMPs) seem to be a promising partner for clinical applications. This overview focuses on the combined application of allograft/BMPs. Current points of view from available literature are summarized.

Mechanical strength of bone allografts subjected to chemical sterilization and other terminal processing methods

Infectious disease transmission through the use of human donor allografts can be a catastrophic complication in an otherwise straightforward surgical procedure. The use of bone allograft in reconstructive orthopedic surgeries is increasing, yet severe complications, including death, can result if the transplanted tissues transmit a communicable disease to the tissue recipient. The BioCleanse tissue sterilization process is a fully automated, low-temperature chemical sterilization process that renders allograft tissue sterile. The purpose of this study was to evaluate the effect of a chemical tissue sterilization process on the mechanical strength of cortical bone allografts prior to implantation. Cylindrical cortical bone specimens were harvested from seven human cadaver donors and treated either by: chemical sterilization alone; chemical sterilization and terminal sterilization by gamma irradiation; chemical sterilization, lyophilization, terminal sterilization by STERRAD and rehydration; or untreated. The specimens were tested to failure in axial compression, diametral compression, shear, or bending. There were no significant differences in ultimate stress, strain, or fracture energy between the chemically sterilized and control groups in any of the testing modes.

Bisphosphonate delivery to tubular bone allografts

Large structural allografts used for reconstruction of bone defects after revision arthroplasty and tumor resection fracture up to 27% of the time from osteolytic resorption around the fixation screw holes and tendon or ligament attachment sites. Treating structural allografts before implantation with bisphosphonates may inhibit local osteoclastic processes and prevent bone resorption and the development of stress risers, thereby reducing the long-term fracture rate. Taking advantage of allografts' open-pore structure, we asked whether passive soaking or positive-pressure pumping was a more efficient technique for delivering bisphosphonates. We treated matched pairs of ovine tibial allografts with fluids containing Tc-99m pamidronate and toluidine blue stain to facilitate indicator distribution analysis via microSPECT-microCT imaging and light microscopy, respectively. Surfactants octylphenoxy polyethoxy ethanol or beractant were added to the treatment fluids to reduce flow resistance of solutions pumped through the allografts. Indicator distribution after 1 hour of soaking produced a thin ring around periosteal and endosteal surfaces, while pumping for 10 minutes produced a more even distribution throughout the allograft. Flow resistance was reduced with octylphenoxy polyethoxy ethanol but unaffected with beractant. Pumped allografts displayed a more homogeneous indicator distribution in less time than soaking while surfactants enhanced fluid movement.

Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3-21.8 kGy) and a moderate absorbed dose (24.0-28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.

Allograft safety in anterior cruciate ligament reconstruction

Allograft tissue seems to provide an excellent option for reconstruction of the ACL in the primary and revision setting. Although in general the risks of using allograft tissue in ACL reconstruction are low, the consequences of complications associated with disease or infection transmission or of recurrent instability secondary to graft failure are large. Surgeons should provide patients with the information available regarding allograft risks and should have thorough knowledge of the source and preparation of the grafts by their tissue bank before implantation for ACL reconstruction.

Direct detection of Clostridium sordellii in pleural fluid of a patient with pneumonic empyema by a broad-range 16S rRNA PCR

We report the case of a 56-y-old male admitted with a left-sided post-pneumonic empyema. Clostridium sordellii DNA was directly detected in its pleural fluid by a broad-range 16S rRNA PCR, after 24 h of specimen collection. This is the third case of pleural infection caused by C. sordellii in the literature.

No influence of collagenous proteins of Achilles tendon, skin and cartilage on the virus-inactivating efficacy of peracetic acid–ethanol

The risk of transmitting human pathogenic viruses via allogeneic musculoskeletal tissue transplants is a problem requiring effective inactivation procedures. Virus safety of bone transplants was achieved using peracetic acid (PAA)-ethanol sterilisation. Proteins are known to have an adverse effect on the virus-inactivating capacity of PAA. Therefore we investigated virus inactivation by PAA in collagenous tissues. Achilles tendon, skin and cartilage were cut into small pieces, lyophilised and contaminated with pseudorabies virus (PRV) or porcine parvovirus (PPV). The inactivating capacity of PAA-ethanol was investigated by determining virus titres in the supernatant or the tissue pellet at different time-points. In all virus-contaminated tissue samples treatment for 10 min with PAA-ethanol resulted in titre reductions by a factor of >10(3). PRV was rapidly inactivated below the detection limit (< or =2.8 x 10(1) TCID(50)/ml). After 240 min a reduction by a factor of >10(4) was obtained for PPV in all samples, but a residual infectivity remained. Collagenous proteins of Achilles tendon, skin and cartilage had no adverse effect on the virus-inactivating capacity of PAA. PAA-ethanol used in the production process at the Charité tissue bank can therefore be recommended for treatment of non-osseous musculoskeletal tissues.

Overview of Procurement, Processing, and Sterilization of Soft Tissue Allografts for Sports Medicine

Musculoskeletal allografts are commonly used in orthopedic surgery and have become increasingly popular. Their indications have widened as an alternatives to autografts. A tissue processing industry has secondarily evolved. An increasing number of accredited tissue banks are providing donor screening, procurement, processing, storage, and distribution of tissue. Multiple factors play a role for a graft to be successfully implanted: sterility, reduction of antigenicity, and preservation of its biologic and biomechanical properties. A rare but catastrophic complication that has raised concern is disease transmission. Controversies exist on which is the best way to produce a strong, disease-free graft. There is no current standard, but as allograft technology evolves, surgeons need to be aware of the regulations and policies surrounding allograft tissue procurement and processing to provide the best outcomes in transplanted patients.

Bone Graft Substitutes in Sports Medicine

Bone graft substitutes are used commonly in orthopedic surgery as an alternative to autograft bone. Autograft bone has the advantages of being osteoconductive, osteoinductive, and osteogenic. However, the quantity of autograft bone available is limited in a given patient and the harvest of autograft bone has been associated with significant morbidity. Bone graft substitutes have become available in an attempt to address these issues and have found widespread use in many areas of orthopedic surgery including sports medicine. The various categories of bone graft substitutes are reviewed here, with an examination of their biologic mechanism of action. Clinical evidence to support their use is also reviewed, with a focus on sports medicine applications.

The routine culture of allograft tissue in anterior cruciate ligament reconstruction

BACKGROUND

Allograft tissue is an acceptable alternative to autograft tissue in anterior cruciate ligament (ACL) reconstruction. However, several infections associated with tissue procurement have led some to consider routine intraoperative cultures of allograft tissue before implantation. A positive culture result presents a treatment dilemma in the asymptomatic patient.

HYPOTHESIS

Treatment of culture swab-positive allograft tissue is unnecessary if there is no evidence of clinical infection.

STUDY DESIGN

Cohort study (prognosis); Level of evidence, 2.

METHODS

Retrospective analysis was performed on 247 cultures taken in 321 consecutive ACL reconstructions from a single surgeon. Allograft cultures were taken intraoperatively before antibiotic washing and implantation. All patients received standard prophylactic antibiotics consisting of intravenous vancomycin and perioperative cefazolin, and were routinely monitored in the postoperative period for signs of infection.

RESULTS

Twenty-four of 247 (9.7%) cultures were positive after implantation. Sixteen of these (67%) grew organisms of high pathogenicity, whereas 8 (33%) were of low pathogenicity. Cultures were classified as poor, scant, or rare in all 24 patients. These patients did not receive additional antibiotics, and none went on to develop septic arthritis or wound complications. The 2 cases of septic arthritis had negative intraoperative cultures.

CONCLUSIONS

Treatment of low-virulence organisms or minimal growth high-virulence organisms is unnecessary if no evidence of clinical infection exists. The results may call into question the utility of routinely culturing allograft tissue as positive results did not correlate with infectious complications.

Present Status and Perspective of Articular Cartilage Regeneration

Because the capacity of articular cartilage for repair is limited, defects are a major clinical problem, and there is at present no satisfactory clinical technique to regenerate cartilage defects. Current clinical practice involves the bone stimulation technique, which breaks subchondral bone to facilitate cartilage repair from bone marrow derived cells and cytokines. This consists of multiple perforations, abrasions, and micro-fractures. However, with this procedure, cartilage defects are repaired with fibrocartilage, which is known to be biochemically and biomechanically different from normal hyaline cartilage and degeneration occurs in the reparative tissue. Autologous chondrocyte implantation (ACI) for repair of human articular cartilage was reported in 1994, and approved by the USA Food and Drug Association in 1997. This procedure has been performed for more than 20000 people all over the world, but its effectiveness is still controversial. Mosaic plasty was explored in the 1990s. Using this procedure, we can repair defects with hyaline cartilage, but the donor site morbidity is unsolved. To explore a new method for cartilage repair, we transplanted autologous culture-expanded bone marrow mesenchymal cells into articular cartilage defects. Clinical symptoms were improred but the repair cartilage was not hyaline cartilage. Further improvement is required. Many investigations have been made in the search for better means of repair, including gene transduction and the addition of growth factors during cell culture. In addition to bone marrow mesenchymal cells, synovial cells, adipocytes, muscle cells, etc. have been evaluated.

Anterior cruciate ligament reconstruction with a porcine xenograft: a serologic, histologic, and biomechanical study in primates

PURPOSE

This study proposes treatment methods to provide a mechanically competent, immunocompatible, and sterile porcine graft for human knee ligament reconstruction.

METHODS

The anterior cruciate ligament (ACL) was reconstructed by using treated porcine patellar tendon grafts or controls of untreated porcine grafts or allografts in 20 rhesus monkeys. Animals were stratified into 2-, 6-, and 12-month postreconstruction cohorts. Serologic and histologic assessments were performed to evaluate host immunological and cellular response. Healing and functional integrity of the ACL reconstructions were assessed by tensile biomechanical testing.

RESULTS

Untreated porcine grafts were acutely resorbed and rejected, whereas treated porcine grafts and allografts were incorporated by the host as functional grafts. Temporal histologic assessment of treated porcine grafts and rhesus grafts revealed gradual host cellular infiltration and graft collagen remodeling through a similar mechanism of ligamentization. Biomechanical evaluations support graft functional integration with no difference between allograft and treated graft reconstructions.

CONCLUSION

Rhesus allograft and treated porcine grafts presented with similar healing profiles in a long-term evaluation of ACL reconstruction.

CLINICAL RELEVANCE

Immunochemical modification and sterilization of porcine patellar tendon grafts may improve initial biocompatibility and long-term functionality of xenografts in musculoskeletal applications.

Mechanical properties of patellar tendon allografts subjected to chemical sterilization

PURPOSE

We tested the hypothesis that the preimplantation mechanical properties of BioCleanse-treated bone-patellar tendon-bone (BPTB) allografts are not significantly different from those of untreated specimens.

METHODS

For this controlled laboratory study, specimens were harvested as central third or hemi-BPTB units from both knees of 17 cadaveric tissue donors (11 men and 6 women) aged 19 to 88 years. Donor-matched specimens (20 per group) were randomly assigned to either BioCleanse-treated or untreated control groups. Specimens were subjected to 25 minutes of pretensioning at 89 N and then cyclically loaded under longitudinal tension between 50 N and 250 N for 1,000 cycles at 1 Hz, followed by ramp to failure at 50 mm/min.

RESULTS

No statistically significant difference was found between untreated and BioCleanse-treated specimens in stiffness (235.3 +/- 37.6 N/mm v 222.3 +/- 53.4 N/mm, P = .37), cyclic creep (0.38 +/- 0.42 mm v 0.40 +/- 0.26 mm, P = .81), maximum force (1,685.7 +/- 471.6 N v 1,807.0 +/- 657.8 N, P = .47), or ultimate stress (29.0 +/- 9.8 MPa v 29.0 +/- 12.8 MPa, P = .98).

CONCLUSIONS

The preimplantation mechanical properties of BPTB allografts treated with BioCleanse are not significantly different from those of untreated controls.

CLINICAL RELEVANCE

This laboratory study compares the biomechanical properties of chemically treated allografts, which are currently being used in anterior cruciate ligament reconstruction, with those of nontreated fresh-frozen allografts.

Infections and human tissue transplants: review of FDA MedWatch reports 2001-2004

BACKGROUND

More than 1.5 million tissue allografts are transplanted annually in the U.S. As part of the federal effort to improve tissue safety, FDA's May 2005 Current Good Tissue Practices (CGTP) Rule requires tissue establishments to report to FDA serious infectious adverse events following allograft transplantation. To provide baseline data, we summarize reports of such infections received by FDA prior to the CGTP Rule.

METHODS

We reviewed reports received by FDA's MedWatch adverse event reporting system during 2001-2004. Our case definition was a reported infection in a human tissue transplant recipient within 1 year of transplantation. We examined demographics, tissue type, clinical outcomes and interventions, infectious organism(s), time from transplant to infection and reporter characteristics.

RESULTS

We identified 83 reports of infections following allograft transplantations. Median patient age was 40 years (range: 1 month-87 years). The allografts included heart valves (42%), tendons (33%), bones (8%), blood vessels (6%), ocular tissues (5%), and skin (4%). Commonly reported outcomes and interventions were hospitalization (72%), antibiotic therapy (46%) and graft removal (42%). Nine of 11 patients who expired had received heart valves. In 65 reports that identified suspected organisms, bacteria were most common (42), followed by fungi (25) and prions (1). The median time from transplant to infection was 5.5 weeks (range: 3 days-52 weeks). Tissue manufacturers submitted 26% of reports. Among the remaining 74%, the reporters were quality assurance staff, infection control or risk management personnel (45%); physicians (15%); consumers (15%); nurses (13%); and surgical staff (12%).

CONCLUSION

This is the first review of reports to FDA for infections following allograft tissue transplantations. Infections led to serious outcomes and involved many tissue types. Although we were unable to confirm that reported infections were caused by the suspected tissue product, required reporting by tissue establishments and improvements in adverse event investigation will help to improve tissue safety surveillance.

Human tissue oversight in hospitals: an AABB survey

BACKGROUND

Reports of human tissue allograft-transmitted infections have underscored the need for better accounting of allografts in health-care facilities. The Joint Commission on Accreditation of Healthcare Organizations (JCAHO) implemented new storage and issuance tissue standards for hospital oversight as of July 1, 2005. This study sought to survey hospital tissue responsibilities.

STUDY DESIGN AND METHODS

The AABB Tissue Task Force conducted a Web-based survey distributed to all 904 hospital institutional members in January 2005. The survey asked about tissue type used, breadth of responsibility, hospital department involvement, and views on AABB involvement. Data from 402 of 904 (45%) respondents were tabulated and analyzed.

RESULTS

Among the 402 respondents, 325 (81%) used allogeneic and/or autologous human tissue. The most frequently used tissues were musculoskeletal (n = 240, 74%) and skin (n = 169, 52%) allografts. The department of surgery (e.g., operating room; n = 245, 76%) most often had responsibility for tissue use, followed by the blood bank (i.e., transfusion service; n = 164, 51%); surgery most frequently had responsibility for all tissue types except peripheral blood progenitor cells. Only 32 of 402 (8%) respondents had plans for increased oversight in the next 12 months; 129 of 178 (72%) thought there was a role for AABB in developing guidance on hospital tissue responsibilities.

CONCLUSIONS

In this survey, most AABB member hospital respondents indicated facility use of allogeneic and/or autologous tissues. Although tissue allograft responsibility by surgery was extensive, hospital blood banks also had significant involvement. Few blood banks, however, plan increased oversight in the near future. Given JCAHO standards, blood banks have an opportunity to assist their hospital in planning for assigned tissue responsibilities and oversight to ensure patient safety.

Bacterial infection transmitted by human tissue allograft transplantation

Bacterial contamination of tissue allografts obtained from cadaveric donors has been a serious cause of morbidity and mortality in recipients. Recent cases of fatal and nonfatal bacterial infections in recipients of contaminated articular cartilage (distal femur) and tendon allografts have called attention to the importance of avoiding tissue donors suspected of carrying infectious disease, of not processing donated tissue carrying virulent bacteria, the occurrence of falsely negative final sterility tests, and the need to sterilize tissues. These cases demonstrated that contamination can arise from an infected donor, during tissue removal from cadaveric donors, from the processing environment, and from contaminated supplies and reagents used during processing. Final sterility testing can be unreliable, especially when antibiotics remain on tissues. There is an increasing need for control of microbial contamination in tissue banks, and sterilization of tissue allografts should be recommended whenever possible.

Overview of safety issues concerning the preparation and processing of soft-tissue allografts

With the increasing use of allograft tissue and the recent infections found in patients undergoing surgical procedures, the current practices that prepare grafts for implantation must be examined. Initially, most tissue banks harvest allografts aseptically. There are many steps in the different techniques of preparation and processing of allograft tissue. Before allograft tissue is ready for clinical use, it undergoes specific disinfection methods, according to the individual tissue bank's specific process. Tissue banks use in-process bactericidal and virucidal steps via physical cleaning, chemical treatments, or application of irradiation to the allografts (or some combination thereof). Gamma irradiation may also be used as a terminal processing method to reach an assurance of sterility after the allograft has been packaged. Because of the allograft toxicity potential, the use of ethylene oxide as a final tissue sterilization measure is really nonexistent. The role of the Food and Drug Administration and American Association of Tissue Banks in allograft tissue handling is presented, as well as the new rules that regulate tissue banks and affect their processing methods.

Culture-Negative Surgical Site Infections

BACKGROUND

The appearance of postoperative surgical site infection (SSI) in the absence of culturable bacterial pathogens is a common dilemma for the surgeon.

METHODS

The literature was searched through references to primary articles, as well as a MEDLINE review, for reports of culture-negative SSIs.

RESULTS

Potential causes of culture-negative SSIs include prior antimicrobial therapy; the presence of fastidious or slow-growing microorganisms such as mycobacteria, Mycoplasma spp., and Legionella spp.; infection caused by mundane bacteria that may be dismissed as "contaminants"; factitious infection; and others.

CONCLUSIONS

We review the recognized causes of "culture negative" SSIs and discuss the laboratory capabilities that may enhance recognition of many of these pathogens and management options.

Clostridium sordellii infection: epidemiology, clinical findings, and current perspectives on diagnosis and treatment

Clostridium sordellii infections pose difficult clinical challenges and are usually fatal. Most commonly, these infections occur after trauma, childbirth, and routine gynecological procedures, but they have recently been associated with medically induced abortions and injection drug use. We report 2 fatal cases, one of which was associated with minor trauma, and the other of which was associated with normal childbirth, and we summarize the clinical features of 43 additional cases of reported C. sordellii infection. Of these 45 cases, 8 (18%) were associated with normal childbirth, 5 (11%) were associated with medically induced abortion, and 2 (0.4%) were associated with spontaneous abortion. The case-fatality rate was 100% in these groups. Ten (22%) of the C. sordellii infections occurred in injection drug users, and 50% of these patients died. Other cases of C. sordellii infection (in 19 patients [43%]) occurred after trauma or surgery, mostly in healthy persons, and 53% these patients died. Overall, the mortality rate was 69% (31 of 45 patients). Eighty-five percent of all patients with fatal cases died within 2-6 days of initial infection, and nearly 80% of fatal cases developed leukemoid reactions. Rapid diagnostic tests and improved treatments are needed to reduced the morbidity and mortality associated with this devastating infection.

Effect of gamma irradiation on viability and DNA of Staphylococcus epidermidis and Escherichia coli

Gamma irradiation is widely used for sterilization; however, its effect on elimination of amplifiable DNA, an issue of relevance to molecular diagnostic approaches, has not been well studied. The effect of gamma irradiation on the viability of Staphylococcus epidermidis and Escherichia coli (using quantitative cultures) and on their DNA (using quantitative 16S rRNA gene PCR) was evaluated. Viability was abrogated at 2.8 and 3.6 kGy for S. epidermidis and E. coli, respectively. The radiation dose required to reduce viable bacteria by one log10 (D10 value) was 0.31 and 0.35 kGy for S. epidermidis and E. coli, respectively. D10 values for amplifiable DNA extracted from bacteria were 2.58 and 3.09 kGy for S. epidermidis and E. coli, respectively, whereas D10 values for amplifiable DNA were significantly higher for DNA extracted from irradiated viable bacterial cells (22.9 and 52.6 kGy for S. epidermidis and E. coli, respectively; P<0.001). This study showed that gamma irradiation of DNA in viable bacterial cells has little effect on amplifiable DNA, was not able to eliminate amplifiable 16S rRNA genes at a dose of up to 12 kGy and cannot therefore be used for elimination of DNA contamination of PCR reaction components or laboratory equipment when this DNA is present in microbial cells. This finding has practical implications for those using molecular diagnostic techniques in microbiology.

The mechanical properties and osteoconductivity of hydroxyapatite bone scaffolds with multi-scale porosity

The relative osteoconductivity and the change in the mechanical properties of hydroxyapatite (HA) scaffolds with multi-scale porosity were compared to scaffolds with a single pore size. Non-microporous (NMP) scaffolds contained only macroporosity (250-350 microm) and microporous (MP) scaffolds contained both macroporosity and microporosity (2-8 microm). Recombinant human bone morphogenetic protein-2 (rhBMP-2) was incorporated into all scaffolds via gelatin microspheres prior to implantation into the latissimus dorsi muscle of Yorkshire pigs. After 8 weeks, only the MP scaffolds contained bone. The result demonstrates the efficacy of the MP scaffolds as drug carriers. Implanted and as-fabricated scaffolds were compared using histology, microcomputed tomography, scanning electron microscopy, and compression testing. Implanted scaffolds exhibited a stress-strain response similar to that of cancellous bone with strengths between those of cancellous and cortical bone. The strength and stiffness of implanted NMP scaffolds decreased by 15% and 46%, respectively. Implanted MP scaffolds lost 30% of their strength and 31% of their stiffness. Bone arrested crack propagation effectively in MP scaffolds. The change in mechanical behavior is discussed and the study demonstrates the importance of scaffold microporosity on bone ingrowth and on the mechanical behavior of HA implant materials.

CHALLENGES IN THE EVALUATION OF SAFETY AND EFFICACY OF HUMAN TISSUE AND CELL BASED PRODUCTS

Human tissue and cell-based therapeutic interventions provide efficacious alternative treatment where traditional drugs or medical devices have proved unsatisfactory. Yet human tissue and cell-based products (HTC/P) still present a series of challenges regarding their safety and efficacy. By reviewing the history of development and current regulatory standards and observing activities related to the manufacture of HTC/P, we have described the common characteristics of HTC/P, including the risk of pathogen transmission, transportation methods of human tissues, quality control in HTC/P manufacturing, and the concern of ancillary materials. The ethical issues of cadaveric donation and clinical trial standards for HTC/P have also been discussed. Overall, we have provided a general standard, which articulates the essential requirements on the safety and efficacy of HTC/P.

Reconstruction of the lateral ankle ligaments with allograft in patients with chronic ankle instability

The management of chronic lateral instability of the ankle remains controversial. In general, the anterior talofibular ligament (ATFL) must be reconstructed in all patients. Some will also need reconstruction of the calcaneofibular ligament (CFL) (or its function) to regain stability of both the ankle and the subtalar joints, and to avoid recurrence of instability. After reconstruction, most authors report good to excellent results in 80% to 85% of patients. We describe the augmented reconstruction technique of ATFL and CFL with a semitendinosus tendon allograft through a peroneal bone tunnel fixed with biodegradable anchors, and advocate this procedure as a safe, effective method to manage lateral ankle instability.