Creutzfeld-Jakob disease: recommendations for infection control

An Efficient Procedure for Removal and Inactivation of Alpha-Synuclein Assemblies from Laboratory Materials

Background: Preformed α-synuclein fibrils seed the aggregation of soluble α-synuclein in cultured cells and in vivo. This, and other findings, has kindled the idea that α-synuclein fibrils possess prion-like properties.

Objective: As α-synuclein fibrils should not be considered as innocuous, there is a need for decontamination and inactivation procedures for laboratory benches and non-disposable laboratory material.

Methods: We assessed the effectiveness of different procedures designed to disassemble α-synuclein fibrils and reduce their infectivity. We examined different commercially available detergents to remove α-synuclein assemblies adsorbed on materials that are not disposable and that are most found in laboratories (e.g. plastic, glass, aluminum or stainless steel surfaces).

Results: We show that methods designed to decrease PrP prion infectivity neither effectively remove α-synuclein assemblies adsorbed to different materials commonly used in the laboratory nor disassemble the fibrillar form of the protein with efficiency. In contrast, both commercial detergents and SDS detached α-synuclein assemblies from contaminated surfaces and disassembled the fibrils.

Conclusions: We describe three cleaning procedures that effectively remove and disassemble α-synuclein seeds. The methods rely on the use of detergents that are compatible with most non-disposable tools in a laboratory. The procedures are easy to implement and significantly decrease any potential risks associated to handling α-synuclein assemblies.

Prions: Beyond a Single Protein

Since the term protein was first coined in 1838 and protein was discovered to be the essential component of fibrin and albumin, all cellular proteins were presumed to play beneficial roles in plants and mammals. However, in 1967, Griffith proposed that proteins could be infectious pathogens and postulated their involvement in scrapie, a universally fatal transmissible spongiform encephalopathy in goats and sheep. Nevertheless, this novel hypothesis had not been evidenced until 1982, when Prusiner and coworkers purified infectious particles from scrapie-infected hamster brains and demonstrated that they consisted of a specific protein that he called a "prion." Unprecedentedly, the infectious prion pathogen is actually derived from its endogenous cellular form in the central nervous system. Unlike other infectious agents, such as bacteria, viruses, and fungi, prions do not contain genetic materials such as DNA or RNA. The unique traits and genetic information of prions are believed to be encoded within the conformational structure and posttranslational modifications of the proteins. Remarkably, prion-like behavior has been recently observed in other cellular proteins-not only in pathogenic roles but also serving physiological functions. The significance of these fascinating developments in prion biology is far beyond the scope of a single cellular protein and its related disease.

A direct assessment of human prion adhered to steel wire using real-time quaking-induced conversion

Accidental transmission of prions during neurosurgery has been reported as a consequence of re-using contaminated surgical instruments. Several decontamination methods have been studied using the 263K-hamster prion; however, no studies have directly evaluated human prions. A newly developed in vitro amplification system, designated real-time quaking-induced conversion (RT-QuIC), has allowed the activity of abnormal prion proteins to be assessed within a few days. RT-QuIC using human recombinant prion protein (PrP) showed high sensitivity for prions as the detection limit of our assay was estimated as 0.12 fg of active prions. We applied this method to detect human prion activity on stainless steel wire. When we put wires contaminated with human Creutzfeldt–Jakob disease brain tissue directly into the test tube, typical PrP-amyloid formation was observed within 48 hours, and we could detect the activity of prions at 50% seeding dose on the wire from 10^2.8 to 10^5.8 SD₅₀. Using this method, we also confirmed that the seeding activities on the wire were removed following treatment with NaOH. As seeding activity closely correlated with the infectivity of prions using the bioassay, this wire-QuIC assay will be useful for the direct evaluation of decontamination methods for human prions.

Effect of heating on the stability of amyloid A (AA) fibrils and the intra- and cross-species transmission of AA amyloidosis

Amyloid A (AA) amyloidosis is a protein misfolding disease characterized by extracellular deposition of AA fibrils. AA fibrils are found in several tissues from food animals with AA amyloidosis. For hygienic purposes, heating is widely used to inactivate microbes in food, but it is uncertain whether heating is sufficient to inactivate AA fibrils and prevent intra- or cross-species transmission. We examined the effect of heating (at 60 °C or 100 °C) and autoclaving (at 121 °C or 135 °C) on murine and bovine AA fibrils using Western blot analysis, transmission electron microscopy (TEM), and mouse model transmission experiments. TEM revealed that a mixture of AA fibrils and amorphous aggregates appeared after heating at 100 °C, whereas autoclaving at 135 °C produced large amorphous aggregates. AA fibrils retained antigen specificity in Western blot analysis when heated at 100 °C or autoclaved at 121 °C, but not when autoclaved at 135 °C. Transmissible pathogenicity of murine and bovine AA fibrils subjected to heating (at 60 °C or 100 °C) was significantly stimulated and resulted in amyloid deposition in mice. Autoclaving of murine AA fibrils at 121 °C or 135 °C significantly decreased amyloid deposition. Moreover, amyloid deposition in mice injected with murine AA fibrils was more severe than that in mice injected with bovine AA fibrils. Bovine AA fibrils autoclaved at 121 °C or 135 °C did not induce amyloid deposition in mice. These results suggest that AA fibrils are relatively heat stable and that similar to prions, autoclaving at 135 °C is required to destroy the pathogenicity of AA fibrils. These findings may contribute to the prevention of AA fibril transmission through food materials to different animals and especially to humans.

Virale Infektionen: RNA-Viren

Rhinoviren sind die Haupterreger der sog. Erkältungskrankheiten. Eine wichtige Rolle spielen sie auch als Auslöser von Asthmaattacken.

Es findet eine stete Kozirkulation mehrerer Serotypen statt, im gemäßigten Klima gibt es Herbst-, Winter- und Frühjahrsepidemien, die Übertragung geschieht weit häufiger über infizierte Sekrete als durch Aerosole.

Rhinoviren gehören zu den Picornaviren. Rhinoviren sind sehr kleine Viren mit einem positiven Einzelstrang-RNA-Genom ohne Lipidhülle und daher gegen Detergens enthaltende Desinfektionsmittel sehr resistent. Sie sind empfindlich gegen Umgebungs-pH außerhalb des Bereichs 5,0–7,5.

Zurzeit bilden sie zusammen mit den Enteroviren das Genus Enterovirus der Picornaviren. Serologisch lassen sich über 100 Typen unterscheiden. Kennzeichnend ist die Bindungsfähigkeit an das von den meisten Rhinoviren für die Zelladsorption genützte ICAM-1 (interzelluläres Adhäsionsmolekül).

Nach einer Inkubationszeit von 1–3 Tagen tritt Schnupfen auf, die höchste Viruskonzentration im Nasensekret nach 2–4 Tagen, wiederum nach 2–4 Tagen bei disponierten Patienten auch bronchiale Obstruktion. Es konnte gezeigt werden, dass zu dieser Zeit auch Virus-RNA im Bronchialepithel vorhanden ist. Die postinfektiöse bronchiale Hyperreagibilität korreliert mit der Dauer des Virus-RNA-Nachweises im Nasopharynx. Die Immunität ist im Wesentlichen abhängig von der nur sehr kurzen Anwesenheit sekretorischer spezifischer IgA-Antikörper. Die bei den Serotypen beobachtbare Kreuzreaktivität spiegelt sich nicht in Kreuzimmunität wider.

Transmission of infection by flexible gastrointestinal endoscopy and bronchoscopy

Flexible endoscopy is a widely used diagnostic and therapeutic procedure. Contaminated endoscopes are the medical devices frequently associated with outbreaks of health care-associated infections. Accurate reprocessing of flexible endoscopes involves cleaning and high-level disinfection followed by rinsing and drying before storage. Most contemporary flexible endoscopes cannot be heat sterilized and are designed with multiple channels, which are difficult to clean and disinfect. The ability of bacteria to form biofilms on the inner channel surfaces can contribute to failure of the decontamination process. Implementation of microbiological surveillance of endoscope reprocessing is appropriate to detect early colonization and biofilm formation in the endoscope and to prevent contamination and infection in patients after endoscopic procedures. This review presents an overview of the infections and cross-contaminations related to flexible gastrointestinal endoscopy and bronchoscopy and illustrates the impact of biofilm on endoscope reprocessing and postendoscopic infection.

Notification and support for people exposed to the risk of Creutzfeldt-Jakob disease (CJD) (or other prion diseases) through medical treatment (iatrogenically)

BACKGROUND

Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD) are rare and always-fatal diseases transmissible via certain medical procedures. If a person is exposed to the disease risk through medical treatment, they may need to be notified of this to prevent them passing the risk to others in healthcare settings and to enable additional infection control measures to be put in place for certain procedures. As CJD is incurable, and unable to be screened for or effectively treated, communicating this risk information after an exposure incident may have significant implications for the person at risk, their families/ carers and healthcare professionals. The best ways to notify people of their exposure to the risk of CJD or vCJD, and to support them subsequently, are currently unknown.

OBJECTIVES

To evaluate the effects of interventions to notify and support consumers (patients and their family members or carers) in situations where exposure to the risk of CJD or vCJD has occurred as a result of medical treatment (iatrogenically), on consumer, healthcare provider and healthcare system outcomes.

SEARCH STRATEGY

We searched the Cochrane Consumers and Communication Review Group Specialised Register (10 February, 2009), the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1 2009), MEDLINE (OVID SP), EMBASE (OVID SP), PsycINFO (OVID SP), CINAHL (EBSCO Host), Current Contents (OVID SP) and Dissertation Abstracts (Proquest) from start date to February 2009. We searched MEDLINE In-process and Other Non-indexed Citations (OVID SP) and Sociological Abstracts (CSA) in November 2009. We searched reference lists, websites, and contacted consumer groups and experts for details of relevant research.

SELECTION CRITERIA

Randomised and quasi-randomised controlled studies, controlled before-and-after studies and interrupted time series analyses assessing the effects of any intervention to communicate with (notify or support) people exposed to the risk of CJD or vCJD through medical treatment were included. We sought outcomes relevant to consumers, health providers and health services, including both benefits and harms.

DATA COLLECTION AND ANALYSIS

Cochrane reviewTwo authors independently assessed studies for inclusion against selection criteria, and would have applied standard Cochrane review methodology were any studies identified.Thematic synthesisWe also conducted a thematic synthesis by systematically identifying and screening those studies that met the same population, intervention and outcome criteria as the Cochrane review, but that were identified from the broader literature providing evidence on policy implementation and consumer experiences. We systematically extracted and synthesised the data from these studies to produce a thematic synthesis, presented in appendices to this Cochrane review, which assembles evidence on the views, experiences and acceptability of notification and support strategies for people at risk.

MAIN RESULTS

Results of the Cochrane reviewNo studies meeting the study design criteria were identified for inclusion in this Cochrane review.Results of thematic synthesisIn total, 49 studies and pieces of literature meeting the same population, intervention and outcome criteria as the Cochrane review, but identified from the broader literature providing evidence on policy implementation and consumer experiences, were included and formed the basis of a thematic synthesis, and which is presented in appendices to this Cochrane review. The thematic synthesis indicates that ideally communication may be considered as a longitudinal multicomponent programme, ensuring that notification and support are coordinated; that communication is tailored and responsive to need; and that activities to support individual risk communication, such as widespread education and monitoring of access to health care for those at risk, are in place. The thematic synthesis also indicates that poor communication practices may have negative impacts or cause harm, such as discrimination in accessing health care.

AUTHORS' CONCLUSIONS

There is insufficient rigorous evidence to determine the effects of interventions to notify people at CJD or vCJD risk and to support them subsequently, or to identify the best approach to communication in these situations. The thematic synthesis can be used to inform policy and practice decisions for communicating with people at risk in the absence of rigorous evaluative studies.

Prion stability and infectivity in the environment

The biology of normal prion protein and the property of infectivity observed in abnormal folding conformations remain thinly characterized. However, enough is known to understand that prion proteins stretch traditional views of proteins in biological systems. Numerous investigators are resolving details of the novel mechanism of infectivity, which appears to feature a protein-only, homologous replication of misfolded isoforms. Many other features of prion biology are equally extraordinary. This review focuses on the status of infectious prions in various natural and man-made environments. The picture that emerges is that prion proteins are durable under extreme conditions of environmental exposure that are uncommon in biological phenomena, and this durability offers the potential for environmental reservoirs of persistent infectivity lasting for years. A recurrent theme in prion research is a propensity for these proteins to bind to mineral and metal surfaces, and several investigators have provided evidence that the normal cellular functions of prion protein may include metalloprotein interactions. This structural propensity for binding to mineral and metal ions offers the hypothesis that prion polypeptides are intrinsically predisposed to non-physiological folding conformations that would account for their environmental durability and persistent infectivity. Similarly, the avidity of binding and potency of prion infectivity from environmental sources also offers a recent hypothesis that prion polypeptides bound to soil minerals are actually more infectious than studies with purified polypeptides would predict. Since certain of the prion diseases have a history of epidemics in economically important animal species and have the potential to transmit to humans, urgency is attached to understanding the environmental transmission of prion diseases and the development of protocols for their containment and inactivation.

Virale Infektionen

Adenoviren verursachen im Kindesalter Krankheiten der Atemwege und des Darms, aber auch Krankheiten der Harnwege, der Lymphorgane und kardiologische und neurologische Manifestationen werden beobachtet. Einige typische Krankheitsbilder können klinisch diagnostiziert werden.

Insulin amyloid fibrillation at above 100 degrees C: new insights into protein folding under extreme temperatures

To investigate the folding behavior of amyloidogenic proteins under extreme temperatures, the kinetics of fibrillation and accompanying secondary structure transitions of bovine insulin were studied for temperatures ranging up to 140 degrees C. The presence of extreme heat stress had traditionally been associated with irreversible denaturation of protein while the initial steps of such a denaturation process may be common with a fibril formation pathway of amyloidogenic proteins. The present work demonstrates the ability of insulin to form amyloid fibrils at above 100 degrees C. Amyloid formation was gradually replaced by random coil generation after approximately 80 degrees C until no amyloid was detected at 140 degrees C. The morphology of insulin amyloid fibrils underwent sharp changes with increasing the temperature. The dependence of amyloid formation rate on incubation temperature followed non-Arrhenius kinetics, which is explained by temperature-dependent enthalpy change for amyloid formation. The intermediate stage of amyloid formation and random coil generation consisted of a partially folded intermediate common to both pathways. The fully unfolded monomers in random coil conformation showed partial reversibility through this intermediate by reverting back to the amyloid pathway when formed at 140 degrees C and incubated at 100 degrees C. This study highlights the non-Arrhenius kinetics of amyloid fibrillation under extreme temperatures, and elucidates its intermediate stage common with random coil formation.

In vitro study of osteogenic differentiation of bone marrow stromal cells on heat-treated porcine trabecular bone blocks

This in vitro study investigated the potential of the heat-treated porcine trabecular bone block as a bone substitute for the treatment of bone defects or related diseases. Chemical, mechanical, and morphological studies of bone blocks were performed. The resultant properties were compared with the properties of currently available commercial products from bovine trabecular bones. The major component of the bone block was hydroxyapatite, and the ratio of Ca/P was 1.65-1.66. The average values of the compressive Young's modulus and the ultimate strength were 346.33 +/- 83.15 and 6.66 +/- 1.62 MPa, respectively. The pore size of the heat-treated bone blocks was approximately 300-500 microm. For the biological investigations, expanded bone marrow stromal cells (BMSCs) were isolated from the femurs of New Zealand White rabbits and were dynamically seeded into the heat-treated porcine bone block (10x10x5 mm3). Before the cells were seeded, the heat-treated porcine bone blocks were divided into two groups: collagen coated blocks (n=16) and uncoated blocks (n=16). Within each group, the blocks were again divided into two groups, depending on the culture method, i.e., static or rotating culture. Cells were cultured in the blocks for up to 6 weeks. Scanning electron microscopic examination after 4 weeks showed that the cell layers attached to the porcine bone block. Proliferation and osteogenic differentiation were analyzed by cell counting, an MTT assay, alkaline phosphatase activity, and total protein content. The deposition of extracellular substances and osteoid formation surrounded by osteoblast-like cuboidal cells were confirmed through histochemical staining and transmission electron microscopy. Based on the results of this study, we conclude that heat-treated porcine trabecular bone has great potential as a bone substitute and may even be superior to currently available commercial products.

Diagnostic challenges in Creutzfeldt-Jakob disease: case report

Sporadic Creutzfeldt-Jakob disease (CJD) is the most common prion disease. The diagnosis can be confirmed only by histological examination of brain tissue obtained at biopsy or at autopsy. Because of the transmissible nature of the disease, autopsy or brain biopsy cannot be performed at many institutions, which poses numerous challenges in confirming the diagnosis. We report the case of a patient with CJD in which autopsy to confirm the diagnosis was performed after overcoming numerous obstacles and advocating with hospital leadership. This case illustrates the numerous challenges that exist in achieving a definitive diagnosis of CJD and in postmortem disposition of the body, and we provide recommendations to clinicians who face similar challenges.

Creutzfeldt-Jakob disease--identifying prions and carriers

Two major obstacles to be overcome in minimizing the possibility of transmitting Creutzfeldt-Jakob disease or variant Creutzfeldt-Jakob disease are associated with identifying the prion on disinfected surgical instruments and identifying carriers of the protease-resistant form of the prion. New developments indicate that the means for doing both soon may be available.

Prions: pathogenesis and reverse genetics

Spongiform encephalopathies are a group of infectious neurodegenerative diseases. The infectious agent that causes transmissible spongiform encephalopathies was termed prion by Stanley Prusiner. The prion hypothesis states that the partially protease-resistant and detergent-insoluble prion protein (PrPsc) is identical with the infectious agent, and lacks any detectable nucleic acids. Since the latter discovery, transgenic mice have contributed many important insights into the field of prion biology. The prion protein (PrPc) is encoded by the Prnp gene, and disruption of Prnp leads to resistance to infection by prions. Introduction of mutant PrPc genes into PrPc-deficient mice was used to investigate structure-activity relationships of the PrPc gene with regard to scrapie susceptibility. Ectopic expression of PrPc in PrPc knockout mice proved a useful tool for the identification of host cells competent for prion replication. Finally, the availability of PrPc knockout and transgenic mice overexpressing PrPc allowed selective reconstitution experiments aimed at expressing PrPc in neurografts or in specific populations of hemato- and lymphopoietic cells. The latter studies helped in elucidating some of the mechanisms of prion spread and disease pathogenesis.

Prion disease and medical devices

Prions are novel proteinaceous-infectious agents that have been implicated in transmissible spongiform encephalopathies. It is now generally accepted that noninfectious prion proteins are normally produced by the host and may undergo a conformational change to an abnormal, pathologic form, which appears to be responsible for disease symptoms. Many methods of decontamination and sterilization are claimed to be ineffective against prion proteins. Incidences of iatrogenic transmission of prions due to medical devices have been reported, and the recommended clinical practices when handling suspected cases are reviewed. Recent results with a peracetic acid based sterilant indicate that it may be a safe and effective means of prion inactivation on medical devices.

Effect of gas composition on spore mortality and etching during low-pressure plasma sterilization

The aim of this work was to investigate possible mechanisms of sterilization by low-temperature gas plasma: spore destruction by plasma is compared with etching of synthetic polymers. Bacillus subtilis spores were inoculated at the bottom of glass vials and subjected to different plasma gas compositions (O(2), O(2)/Ar, O(2)/H(2), CO(2), and O(2)/CF(4)), all known to etch polymers. O(2)/CF(4) plasma exhibited much higher efficacy than all other gases or gas mixtures tested, with a more than 5 log decrease in 7.5 min, compared with a 2 log decrease with pure oxygen. Examination by scanning electron microscopy showed that spores were significantly etched after 30 min of plasma exposure, but not completely. We speculate about their etch resistance compared with that of synthetic polymers on the basis of their morphology and complex coating structure. In contrast to so-called in-house plasma, sterilization by Sterrad(R) tended to increase the observed spores' size; chemical modification (oxidation), rather than etching, is believed to be the sterilization mechanism of Sterrad(R).

Mad cow disease--the OR connection

Creutzfeldt-Jakob disease (CJD) is one of the transmissible spongiform encephalopathies, a group of fatal, neurodegenerative disorders affecting both humans and animals. The causative agent is the prion, which is still being researched and is controversial. In the 1980s, bovine spongiform encephalopathy brought much media attention to these diseases. Bovine spongiform encephalopathy is the result of faulty industrial practices that produced cattle feed contaminated by prions. In the 1990s, a new variant of CJD (i.e., nvCJD) appeared in Britain. Researchers believe that nvCJD was passed to humans through oral consumption of contaminated beef. This article describes the history, causative agent, mode of transmission, clinical features and course, diagnosis, treatment, and decontamination and sterilization guidelines for this baffling disease.

Reuse of angioplasty catheters and risk of Creutzfeldt-Jakob disease

BACKGROUND

In 1996, the Quebec Ministry of Health and Social Services, concerned that reuse of devices contaminated with blood or blood products could cause the transmission of Creutzfeldt-Jakob disease (CJD), discontinued its practice of reusing angioplasty catheters despite the significant cost savings reuse had afforded the health care system for several years. The objective of this study was to establish whether the medical literature provides documentation of any cases in which CJD was transmitted by reused percutaneous transluminal coronary angioplasty (PTCA) equipment.

METHODS AND RESULTS

A Medline search was performed to identify previous studies that examined this issue. Key words for the search included PTCA, CJD, and material and equipment reuse. A substantial amount of effort has been spent on the study of PTCA catheter reuse in relation to the risk of infection, toxicity, and catheter breakage as well as cost. In Québec, studies by the Conseil d'Evaluation des Technologies de la Santé investigated the effectiveness of cleaning and sterilizing PTCA equipment and considered the possibility that reuse of single-use catheters, hemodialyzers, and cardiac pacemakers could spread CJD. A number of other studies found evidence that iatrogenic transmission was responsible for several cases of CJD by direct implantation in or adjacent to the central nervous system during neurosurgery. CJD was also transmitted to human beings by injection of pituitary growth hormone and to mice through cerebral inoculation of contaminated blood and urine. However, there were no documented cases of CJD occurring as a complication of PTCA equipment reuse.

CONCLUSIONS

The current literature indicates that there are no known cases of CJD attributable to the reuse of PTCA devices contaminated by blood or to the transfusion of blood or blood products. This practice is associated with a very low risk of CJD transmission. With the considerable cost savings made possible by reuse of PTCA equipment, reimplementation of this practice should be considered by health delivery systems, provided that stringent methods of cleaning and sterilization are observed.

Biomechanical properties of sterilized human auditory ossicles

Bone allograft material is treated with sterilization methods to prevent the transmission of diseases from the donor to the recipient. The effect of some of these treatments on the integrity of the bone is unknown. This study was performed to evaluate the effect of several sterilization methods on the mechanical behaviour of human middle ear bones. Due to the size and composition of the bones (approximately 1.5 mm diameter by 4 mm long), mechanical testing options were limited to the traditional platens compression test. Experiments were first performed with synthetic bone to evaluate the precision of this test applied to small specimens. Following this, fresh frozen human ossicles were thawed and sterilized with (i) 1 N NaOH (n = 12); (ii) 0.9% LpH, a phenolic solution (n = 12); or (iii) steam at 134 degrees C (n = 18). A group of 26 control specimens did not receive any sterilization treatment. Material and structural properties were determined from axial compression testing. Results from the synthetic bone showed that the test was reproducible, with standard deviations less than 20% of the means. Significant differences occurred in stiffness and ultimate force values between NaOH-treated and autoclaved bones when compared to normals (p<0.05), but not for LpH-treated bones. LpH is not approved for medical use, so NaOH is the most appropriate of the treatments studied for the sterilization of ossicle allografts.

Radiologic and mechanical properties of inactivated ossicle homografts

OBJECTIVE

This study examined the effects of old and new inactivation (sterilization) techniques on the radiologic and mechanical properties of ossicle homografts.

MATERIALS AND METHODS

Ninety normal incuses and malleuses received either treatment with 1) 5% formaldehyde/cialit, 2) 1N NaOH, 3) 0.9% LpH, or 4) autoclaving at 134'C, or no treatment. All ossicles were assessed radiologically by high-resolution computed tomography. After imaging, all ossicles underwent mechanical testing by destructive axial compression in a mechanical testing machine measuring force and displacement.

RESULTS

Ossicles treated with cialit, NaOH, or autoclaving showed a significant decrease of ultimate force and stiffness compared with controls. LpH treatment caused no such changes in these structural properties. Material properties of yield strength, ultimate strength, and elastic modulus were also altered by cialit, NaOH, and autoclaving, but were much more difficult to assess because of uncertainty in parameter estimates. There was a significant increase in radiologic density in autoclaved ossicles, a reduction in cialit- and LpH-treated ossicles, and no change in NaOH-treated ossicles.

CONCLUSIONS

All tested inactivation procedures changed the biomechanical and/or radiologic properties of ossicle homografts. However, the new procedures used to inactivate infectious agents produced changes similar to the older treatments with formaldehyde/cialit. Human allografts are able to withstand harsh but safe sterilization procedures. The NaOH treatment seems to be the most suitable method for the future. The biologic (osteogenic) potentials of ossicle homografts treated with these new preservation/inactivation methods are still unknown. Further investigations are necessary to re-evaluate the clinical use of ossicle homografts in middle ear reconstructive surgery.

Exposure Workups

Exposure workups are an important responsibility for infection control personnel. A well-designed plan for investigating exposures, which includes appropriate algorithms, will enable infection control personnel to evaluate exposures rapidly and consistently so that nosocomial transmission is minimized. Infection control personnel should use their own data to develop policies and procedures that suit the needs of their facility. After they have imple-merited the plan, infection control personnel should continue to collect data on exposures so they can continuously improve their performance.