Polymer materials for the prevention of catheter-related infections

Catheter-related infections are major problems in medicine because of severe consequences for the patient, prolongation of hospitalization, and increasing therapy costs. Beside progress in hygienic measures, development of catheters with antiinfective properties seems to be a promising approach to the prevention of such infections. Two approaches for infection-resistant catheter materials have been developed: materials with antiadhesive properties and materials with antimicrobial properties. Antiadhesive polymers shall prevent the adhesion of microorganisms to the medical device. However, up to now there has been no material which would lead to a complete inhibition of adherence ("zero adherence"). Materials with antimicrobial properties contain antimicrobial substances which are incorporated into the biomaterial or bound to the polymer surface. These devices seem to be effective in the prevention of "early onset infections". In this paper, an overview of the development and efficiency of antiadhesive or antimicrobial polymers is given.

Prevention of catheter-related infections by silver coated central venous catheters in oncological patients

Catheter-related infection (CRI) is a serious complication of central venous catheterization. We have investigated the efficacy of a silver-coated polyurethane catheter (Pellethane, Fresenius AG, Germany) in preventing CRI in oncological patients receiving chemotherapy in a phase II study. From November 1992 through April 1994, 266 patients were assigned to receive single lumen catheters, either standard uncoated catheters (UC, n = 113) or silver-coated ones (SC, n = 120). Catheters were inserted into the internal jugular vein after institutional approval and informed consent. Duration of catheterization (UC vs. SC = 13.3 vs. 12.7 days) and leukopenia (< 1.0 x 10(9) WBC/l; 4.3 vs. 3.6 days) were similar in both groups demonstrating a comparable risk for infections. Skin reactions at the catheter entry site were recorded daily. CRI and colonization rates were studied by semiquantitatively culturing intradermal and intravascular segments. CRI were confirmed by blood cultures obtained via catheter and from peripheral veins in cases of suspected sepsis or at the end of catheterization. No adverse effects from the silver-coated catheter could be observed. The bacteriological results showed that SC were colonized (> 15 CFU) in 45.1% and UC in 44.2%. CRI developed in 21.2% of the UC patients but only in 10.2% of the SC patients (p = 0.011). We conclude that this new silver-coated central venous catheter is biocompatible and effective in reducing the incidence of catheter-related infections in oncological patients.

Prevention of biofilm formation by polymer modification

Bacterial biofilm formation on synthetic polymers plays an important role in industry and in modern medicine, leading, for example, to difficult-to-treat infections caused by colonized foreign bodies. Prevention of biofilm formation is a necessary step in the successful prophylaxis of such infections. One approach is to inhibit bacterial adherence by polymer surface modification. We have investigated polymer modification by glow discharge treatment in order to study the influence of the modified surface on bacterial adherence. Surface roughness, surface charge density and contact angles of the modified polymers were determined and related to the adherence of Staphylococcus epidermidis KH6. Although no influence of surface roughness and charge density on bacterial adherence was noticed, a correlation between the free enthalpy of adhesion (estimated from contact angle measurements) and adherence was observed. There seems to exist a certain minimum bacterial adherence, independent of the nature of the polymer surface. Modified polymers with negative surface charge allow for bacterial adherence close to the adherence minimum. These polymers could be improved further by the ionic bonding of silver ions to the surface. Such antimicrobial polymers are able to prevent bacterial colonization, which is a prerequisite for biofilm formation. It is suggested that modification of polymers and subsequent surface coupling of antimicrobials might be an effective approach for the prevention of bacterial biofilm formation.

Susceptibility of staphylococci and enterococci to glycopeptides comparison of 3 test methods

The significance of grampositive bacteria, especially staphylococci and enterococci, as nosocomial pathogens has increased in the last decade. Furthermore, resistance to commonly used antibiotics like beta-lactams has also become more common and even resistance to glycopeptides has been observed. We evaluated the susceptibility of 150 staphylococcal clinical isolates (52 S. epidermidis, 52 S. haemolyticus, 10 S. saprophyticus, 10 S. hominis, 4 S. warneri, 4 S. simulans, 4 S. capitis and 14 S. aureus) and of 50 enterococci (49 E. faecalis, 1 E. faecium) to the glycopeptides, vancomycin and teicoplanin. The data from the agar dilution test used as reference method were compared with the results from the E test and the agar disk diffusion test. Concerning vancomycin, no resistance among all the staphylococcal isolates was observed whereas one single enterococcal strain (E. faecium) proved to be resistant. The overall resistance of staphylococcal isolates against teicoplanin was about 10.7% (15 S. haemolyticus, 1 S. epidermidis) being mainly due to the high proportion of S. haemolyticus strains (52 out of 150) among the staphylococcal isolates. Teicoplanin resistance among the enterococci was not detected. For vancomycin, a very close correlation between the MICs from the agar dilution test and the E test was noticed. As concerns teicoplanin, the MICs from the E-test were usually somewhat lower than those obtained by the agar dilution test. No correlation was found between the MICs of resistant and intermediate staphylococcal strains and the results from the teicoplanin agar disk diffusion test. For routine teicoplanin susceptibility testing of staphylococci, the determination of the MIC (e.g., by the E test) is much more reliable for detecting resistant strains than the agar disk diffusion test.

In vitro and in vivo efficacy of a rifampin-loaded silicone catheter for the prevention of CSF shunt infections

Infection of cerebrospinal fluid (CSF) shunts is one of the major complications associated with their use and is usually managed by shunt removal, temporary insertion of an external drainage and implantation of a new shunt system. We have evaluated the efficacy of a rifampin-loaded silicone ventricular catheter to prevent bacterial colonization and infection in vitro and in an animal model. On the basis of an incorporation process a rifampin-loaded catheter was developed which is capable of releasing rifampin in bacteriocidal concentrations for 60 days and more. In a stationary bacterial adherence assay using S. epidermidis as test strain, the colonization resistance of the device was demonstrated. To assess the capability of the catheter to prevent CSF shunt infections, a rabbit model was developed which allowed the establishment of a reliable and reproducible CSF infection by implantation of silicone catheters into the ventricle and inoculating S. epidermidis (minimal dose 10(6) cfu) or S. aureus (minimal dose 10(3) cfu). Rifampin-loaded catheters (12 animals inoculated with S. epidermidis, 8 animals inoculated with S. aureus) were compared with non-loaded (14 animals inoculated with S. epidermidis, 19 animals inoculated with S. aureus) control catheters, and infection was documented by clinical, microbiological and histological methods. In contrast to the control group, none of the animals with rifampin-loaded catheters showed clinical signs of infection. Furthermore, in none of the materials obtained after sacrifice of the animals (catheter, brain tissue, CSF, blood) could the infecting bacteria be cultured, whereas in materials from animals with the unloaded catheter the infecting strains could always be cultured from the catheter and from surrounding brain tissue. The histological examination of catheter-adjacent tissue supported these findings. We conclude that a rifampin-loaded silicone ventricular catheter is capable of completely preventing bacterial colonization and infection by staphylococci as the main causative organisms in CSF shunt infections and should be further evaluated in clinical trials.

Phosphorothioate oligonucleotides reduce melanoma growth in a SCID-hu mouse model by a nonantisense mechanism

In our efforts to investigate the biologic role of Ha-ras oncogenes in human melanoma by Ha-ras phosphorothioate antisense oligonucleotides, we observed that antisense, sense, and scrambled control oligonucleotides at a concentration of 10 microM all similarly and strongly inhibited growth of our human melanoma target cell line SK-2 in vitro but without specific decrease of the target protein. Cell numbers with respect to the untreated control were reduced by 84% +/- 4.2% (ISD), 82.9% +/- 3.6%, and 84% +/- 3%, respectively. In vivo studies in a SCID-hu mouse model confirmed these findings. Both antisense and sense control oligonucleotides administered through osmotic pumps significantly (p < 0.006) reduced the mean tumor weight (1.5 g +/- 0.4 g and 1.8 g +/- 0.8 g, respectively) in comparison with saline-treated (5.7 g +/- 0.7 g) or untreated control animals (5.8 g +/- 1.0 g). The vascularity of oligonucleotide-treated tumors was greatly reduced. Clinical signs of oligonucleotide-related toxicity were not observed, and there was no evidence of histopathologic alterations in a variety of mouse tissues. We could demonstrate that the antimelanoma effects can be abrogated in vitro by adding basic fibroblast growth factor (bFGF). In the context of the importance of bFGF in melanocyte biology and angiogenesis, we argue in favor of an interaction between polyanionic phosphorothioate oligonucleotides and bFGF in our melanoma system. These findings stress the notion that phosphorothioate oligonucleotides may be promising antineoplastic lead compounds capable of employing antitumor effects by mechanisms other than specific inhibition of gene expression.

In-vitro efficacy of an antibiotic releasing silicone ventricle catheter to prevent shunt infection

Infection due to implanted polymeric devices is a major problem in modern medicine. Microbial colonization of implants in neurosurgery, e.g. cerebrospinal fluid (CSF) shunts is the main reason for their failure, and often results in the consequent removal of the infected implants. In this paper we report on new approaches in the prevention of bacterial infections by incorporation of an antibiotic (rifampicin) into the polymer devices (silicone). Drug release characteristics are investigated, and the physico-chemical mechanism of the delivery is discussed. Measurements of killing kinetics and the bacterial adhesion to the antibiotic-loaded silicone in a static adhesion assay reveal that only the liberation of high antibiotic doses over a period of weeks can prevent the bacterial colonization of the polymeric surface.

In vitro evaluation of the antimicrobial efficacy and biocompatibility of a silver-coated central venous catheter

Central venous catheter infection presents an important problem in modern medicine, leading sometimes to a life-threatening situation for the patient as well as contributing to prolonged hospital stay and to an increase in costs. We have evaluated the in vitro biocompatibility and antimicrobial activity of a silver-coated polyurethane catheter designed for use as a colonization-resistant, antiinfective catheter. Due to a comparatively low silver release, the catheter performed well in cell toxicity and blood compatibility tests as well as in acute toxicity tests done with mice. The antimicrobial activity was tested in stationary and dynamic bacterial adherence experiments using S. epidermidis, E. coli and P. aeruginosa as test strains. The silver-coated polyurethane catheter showed good ability to prevent microbial colonization of the catheter surface. Currently a clinical trial of the silver-coated catheter is under investigation.

Outbreak of methicillin-resistant Staphylococcus aureus in a teaching hospital--epidemiological and microbiological surveillance

An outbreak of methicillin-resistant S. aureus (MRSA) in a large university teaching hospital occurred between December 1991 and May 1992, involving 7 different wards and more than 30 patients. Epidemiological typing was performed to control the epidemic and to identify the MRSA carriers. By a combination of various classical methods (antimicrobial susceptibility, phage typing) and molecular typing procedures (SDS-PAGE of extracellular proteins, plasmid DNA profile, restriction enzyme fragment pattern of chromosomal DNA), three different clones of MRSA could be discriminated. The epidemic clone A was recovered from 30 patients and from 3 staff members. By strict microbiological monitoring together with hygienic measures, the epidemic could be successfully controlled. It is concluded that a combination of phenotypic markers and DNA-based epidemiological markers is extremely useful in the microbiological surveillance of MRSA outbreaks.

Bacterial adherence to hydrophilic polymer-coated polyurethane stents

Biliary stent blockage by adherence of bacteria and formation of biofilm is a major problem in endoscopic stenting procedures. We have investigated bacterial adherence to hydrophilic polymer (Hydromer)-coated polyurethane stents in stationary and perfusion experiments. Adherence of gram negative and gram positive organisms under stationary conditions was similar between Hydromer-coated and non-coated control polyurethane stents; however, a marked 1 to 3 log reduction in adherence to Hydromer-coated stents occurred when perfusion experiments in phosphate buffer solution or bile were performed. The results suggest that Hydromer-coated polyurethane stents could be useful in preventing complications caused by biliary stent blockage.

Foreign body associated infection

One of the major complications associated with the use of medical devices and implants is foreign body associated infection. Its significance in modern medicine and its pathogenesis are discussed. Adherence to and colonization of a foreign body material and the interference of microbial products with the host defence are critical steps leading to foreign body infections. Therapy is difficult and hence the immediate administration of antibiotics and the removal of an infected device or implant is still preferred. New strategies for the prevention of foreign body infections are briefly introduced.

Localization of the ActA polypeptide of Listeria monocytogenes in infected tissue culture cell lines: ActA is not associated with actin "comets"

The ActA protein of the gram-positive pathogen Listeria monocytogenes is a 90-kDa polypeptide required for interaction of the bacteria with components of the host cell microfilament system to generate intra- and intercellular movement. To study the localization, distribution, and expression of the ActA polypeptide in L. monocytogenes grown either in broth culture or in infected tissue culture cells, we first isolated ActA by monoclonal antibody-based immunoaffinity chromatography. Polyclonal rabbit antisera raised against purified ActA revealed that ActA was associated with the cell wall and exposed on the surface of the bacteria, readily accessible to ActA antibodies. In contrast, a C-terminally truncated ActA1 polypeptide expressed by the isogenic actA1 mutant was detected only in the supernatant fluids. Immunofluorescence microscopy and electron microscopic studies using immunogold labeling showed that ActA was present on the surface of the bacteria infecting PtK2 and J774 cells at all stages of the infection cycle and was not found to be associated with the actin "tail" of individual bacteria. For the isogenic actA1 mutant strain, which grew as microcolonies within infected cells, only diffuse staining of the secreted ActA1 polypeptide in the host cytoplasm was observed. The ActA polypeptide therefore appears to be required in the initiation of actin accumulation by the bacterium and is apparently not directly involved in the generation of the actin tail. Analysis of strains of several L. monocytogenes serotypes indicated microheterogeneity in the molecular weights of the ActA polypeptides of individual strains and led to the detection of a serotype 3a strain that does not produce ActA.

Effective immunochemotherapy of human t(4;11) leukemia in mice with severe combined immunodeficiency (SCID) using B43 (anti-CD19)-pokeweed antiviral protein immunotoxin plus cyclophosphamide

Human mixed lineage leukemia cell line RS4;11 with the t(4;11)(q21;q23) translocation causes disseminated and invariably fatal leukemia in mice with severe combined immunodeficiency. Whereas an immunotoxin constructed from the murine anti-CD19(B43) monoclonal antibody and the plant toxin pokeweed antiviral protein (B43-PAP) has a potent in vitro anti-leukemic effect against clonogenic RS4;11 cells, its activity is further potentiated by the active cyclophosphamide congener mafosfamid. These intriguing observations prompted us to evaluate the in vivo antileukemic efficacy of combined immunochemotherapy employing B43-PAP immunotoxin plus cyclophosphamide against human t(4;11) leukemia cells in an RS4;11 severe combined immunodeficiency (SCID) mouse model system. Intravenous injections of B43-PAP or cyclophosphamide improved survival of SCID mice challenged with RS4;11 leukemia, as reflected by markedly prolonged median survival times. After intravenous inoculation of 5 x 10(7) RS4;11 leukemia cells, the median survival times were 41 days for saline-treated control mice (n = 12), 44 days for control mice treated with unconjugated B43 monoclonal antibody and PAP (n = 12), 56 days for mice treated with the control immunotoxin G17.2 (anti-CD4)-PAP (n = 6), 79 days for B43-PAP-treated test mice (n = 12), and 80 days for cyclophosphamide-treated test mice (n = 16). Notably, combined immunochemotherapy using B43-PAP plus cyclophosphamide was significantly more effective than either B43-PAP or cyclophosphamide alone. The median survival time for a total of 22 SCID mice undergoing combined immunochemotherapy with B43-PAP followed by cyclophosphamide (n = 12) or cyclophosphamide followed B43-PAP (n = 10) was > 150 days. The Kaplan-Meier estimates and standard errors of the probability of event-free survival at 5 months after inoculation of 5 x 10(7) RS4;11 cells were 21 +/- 13% for B43-PAP-treated mice, 7 +/- 6% for cyclophosphamide-treated mice, 90 +/- 10% for mice treated with B43-PAP followed by cyclophosphamide (n = 12), and 90 +/- 10% for mice treated with cyclophosphamide followed by B43-PAP (n = 10). Our results lead us to recommend that initial consideration be given to combined immunochemotherapy protocols using B43-PAP immunotoxin plus cyclophosphamide for treatment of refractory or relapsed t(4;11) leukemias.

[New strategies for the prevention of foreign body infections]

Foreign body infections continue to present a challenge to modern medicine. New aspects for the prevention of such infections are presented on the basis of modifying medical devices or implant materials (synthetic polymers). Physicochemical treatment of polymer surfaces is a possible tool to create anti-adhesive and thus anti-infective surfaces. Coupling or incorporation of antimicrobial substances to or into polymers is another way to prevent bacterial colonization and subsequently the development of polymer-associated infections.

In-vitro efficacy of a central venous catheter (‘Hydrocath’) loaded with teicoplanin to prevent bacterial colonization

A technique is described by which a central venous catheter ('Hydrocath') is loaded with the glycopeptide teicoplanin for the prevention of catheter infection. Catheters are immersed in teicoplanin solution and, due to the hydrophilic surface coating of the 'Hydrocath' catheter, teicoplanin is absorbed by the surface layer. The catheter loading is influenced by the experimental conditions and is assessed by measuring teicoplanin elution from the catheter using a bioassay. Increasing the antibiotic concentration, incubation time and temperature leads to the binding of higher amounts of teicoplanin to the catheter, resulting in a higher teicoplanin release from the catheter. Experiments on in-vitro bacterial adherence to teicoplanin-loaded and unloaded catheters reveal that the initial bacterial adhesion is not prevented. However, in the case of the teicoplanin-loaded catheter initially adherent bacteria are eliminated from the catheter surface, thus preventing catheter colonization by bacteria for at least 48 h. Such loaded catheters could be suitable for inhibiting early-onset, catheter-related infections.

In-vitro efficacy of a central venous catheter complexed with iodine to prevent bacterial colonization

Infections of central venous lines are still a problem in daily medicine. Despite adequate antibiotic therapy, removal of an infected catheter often becomes necessary. A simple procedure has been developed by which a special hydrophilic central venous catheter (Secalon-Hydrocath) can be loaded with iodine. Iodine is complexed in the hydrophilic polyvinylpyrrolidone surface coating of the Hydrocath catheter and is released during contact with an aqueous medium. The amount of complexed iodine depends on the incubation time in Lugol's solution. Antimicrobial activity of the loaded catheters was assessed with Staphylococcus epidermidis, showing complete inhibition of bacterial adherence to the catheters for the duration of iodine release. Depending on the experimental conditions, iodine released from the catheter is also active on bacteria in the surrounding medium.

Successful treatment of human acute T-cell leukemia in SCID mice using the anti-CD7-deglycosylated ricin A-chain immunotoxin DA7

The study of new therapeutic approaches for refractory human leukemia has been hampered by the lack of relevant in vivo models with disseminated disease, particularly T acute lymphoblastic leukemia (T-ALL). In the present study we evaluated methods for establishing and therapy of a human T-ALL cell line (MT-ALL) in 73 SCID mice. MT-ALL is a T-cell receptor alpha/beta +, CD3+, and CD7+ leukemia cell line, derived from a patient with refractory disease and early death. Injection of 5 x 10(7) MT-ALL cells i.v. caused disseminated human leukemia in hematopoietic and nonhematopoietic organs in 100% of SCID mice (n = 9) leading to death or terminal disease at 65 to 70 days after a uniform clinical course. To study possible therapeutic approaches for disseminated leukemia we utilized an immunotoxin, DA7, constructed by chemically linking the mouse IgG2b anti-CD7(3A1E) monoclonal antibody which recognizes a pan-T-cell marker expressed on almost all T-cell leukemias to deglycosylated ricin A-chain, a catalytic plant toxin and inhibitor of protein synthesis. Administration of DA7 led to greater than 5 log kill of clonogenic MT-ALL cells in vitro and selectively inhibited protein synthesis. DA7 was administered to mice at a dose of 10 micrograms/mouse/day for 5 consecutive days starting 8 days after i.v. inoculation of leukemia. The immunotoxin therapy resulted in significant long term survival over 348 days compared to untreated or control mice treated with anti-CD7 antibody and deglycosylated ricin A-chain which were all dead by day 70 (P less than 0.001). Even after more than 11 months there was no evidence of disease in 82% of the DA7 treated animals. SCID mice given i.p. injections (n = 9) developed an i.p. tumor mass but demonstrated metastasis outside the peritoneum with disseminated leukemia in hematopoietic and nonhematopoietic organs, a finding different from most conventional nude mouse models. The leukemia was fatal in 100% and killed the animals at 68-95 days. SCID mice given i.p. injections of MT-ALL completely responded to therapy with DA7, resulting in survival of 100% of the animals (n = 10) at 216 days (P less than 0.001 compared to untreated animals). Anti-CD7 antibody, deglycosylated ricin A-chain, and a control anti-melanoma immunotoxin (IND1-RTA) showed no therapeutic effect. We conclude that DA7 is an effective in vivo therapeutic agent against human MT-ALL in the SCID mouse system, suggesting potential usefulness for therapy of humans with poor prognosis T-cell leukemia.

Establishment of a human t(4;11) leukemia in severe combined immunodeficient mice and successful treatment using anti-CD19 (B43)-pokeweed antiviral protein immunotoxin

Human acute leukemia, with a chromosomal translocation involving chromosomes 4 and 11, t(4;11)(q21;q23), is the most common form of leukemia in infants and responds very poorly to conventional therapy. A human CD19+ mixed-lineage leukemia cell line with a t(4;11)(q21;q23) translocation, RS4;11, disseminated and proliferated in the hematopoietic tissues and other organs of mice with severe combined immunodeficiency in a manner similar to that observed in humans and killed 100% of the animals. The anti-CD19(B43)-pokeweed antiviral protein immunotoxin selectively inhibited clonogenic RS4;11 cells in vitro, markedly reduced the burden of disseminated leukemia of severe combined immunodeficient mice, and, most importantly, resulted in the long-term survival of treated animals. This severe combined immunodeficient mouse model should be useful for the design of more effective treatment strategies for refractory human leukemias.

Adhesion of fimbriated and non-fimbriated Klebsiella strains to synthetic polymers

Adherence of three fimbriated and non-fimbriated Klebsiella strains to polyetherurethane was investigated in order to assess the possible role of fimbriae in the adhesion of Klebsiella to synthetic polymers. Fimbriated strains with type 1 and type 1.3 fimbriae adhere significantly stronger to polyurethane than the same strains lacking fimbriae, whereas a strain with type 3 fimbriae shows no different adherence compared with the non-fimbriated variant. Analysis of adhesion kinetics and isotherms reveals that adherence of fimbriated Klebsiella strains is proceeded by the formation of multicellular bacterial layers on the polymer surface. Measurements of the relative hydrophobicity of the strains and adherence experiments under exclusion of unspecific interactions point out that fimbriae obviously play a more important role in adhesion than relative hydrophobicity. The demonstration of reduction of bacterial adherence to polyetherurethane by blocking fimbrial action with fimbriae-specific sugars supports this further.

Evidence for degradation of synthetic polyurethanes by Staphylococcus epidermidis

The survival of Staphylococcus epidermidis strain KH 11 in the presence of synthetic high molecular polyurethanes was prolonged in comparison to control experiments performed in the absence of any nutrients. Investigations of the bacteria after contact with the polymers revealed changes in their surface properties and metabolism, in particular a marked induction of urease activity. ESCA (Electron Spectroscopy for Chemical Analysis) measurements detected a decrease in elementary nitrogen in the polyurethane surfaces after incubation with the bacteria. The alterations observed indicate an urease-induced degradation of synthetic polymers by Staphylococcus epidermidis KH 11.

Differentiation in mature T lymphoid leukemia cells is unstable and reversible to myeloid cells, without the involvement of a common stem cell

Mechanisms for the unstable and reversible differentiation of a mature CD3+ CD7+TCR-alpha/beta+ T lymphoid leukemia into the myeloid lineage were investigated. Inasmuch as productive rearrangement of the TCR-alpha is a late determinant of T cell differentiation, the TCR-alpha rearrangement was sequenced to determine the state of differentiation of the leukemic multipotent cell. An identical productive rearrangement of J alpha C to a novel V alpha region was found in the myeloid and T lymphoid leukemic cells. Thus, a "terminally" differentiated T lymphoid leukemic cell after productively rearranging TCR-alpha and -beta continues to display potential for multilineage differentiation. Therefore, multilineage potential is due to an unstable and reversible differentiation in a mature T lymphocyte as opposed to differentiation of an uncommitted common T and myeloid precursor cell.

Differentiation in mature T lymphoid leukemia cells is unstable and reversible to myeloid cells, without the involvement of a common stem cell

Mechanisms for the unstable and reversible differentiation of a mature CD3+ CD7+TCR-alpha/beta+ T lymphoid leukemia into the myeloid lineage were investigated. Inasmuch as productive rearrangement of the TCR-alpha is a late determinant of T cell differentiation, the TCR-alpha rearrangement was sequenced to determine the state of differentiation of the leukemic multipotent cell. An identical productive rearrangement of J alpha C to a novel V alpha region was found in the myeloid and T lymphoid leukemic cells. Thus, a "terminally" differentiated T lymphoid leukemic cell after productively rearranging TCR-alpha and -beta continues to display potential for multilineage differentiation. Therefore, multilineage potential is due to an unstable and reversible differentiation in a mature T lymphocyte as opposed to differentiation of an uncommitted common T and myeloid precursor cell.

Modern strategies in the prevention of polymer-associated infections

Foreign body infections continue to present a challenge to modern medicine. New aspects for the prevention of such infections are presented on the basis of modifying medical devices or implant materials (synthetic polymers). Physicochemical treatment of polymer surfaces is a possible tool to create anti-adhesive and thus anti-infective surfaces. Coupling or incorporation of antimicrobial substances to or into polymers is another way to prevent bacterial colonization and subsequently the development of polymer-associated infections.

[Problems of infection in polymer implants]

Infections associated with indwelling devices have become a major problem in modern medicine. Coagulase-negative staphylococci and to a lesser extent Staphylococcus aureus, enterobacteriaceae und fungi are the predominant causative organisms in the etiology of these infections. The general features of the pathogenesis of foreign body infections are discussed, as are the clinical picture and therapy. Special emphasis is given to the occurrence of polymer-associated infections in urological devices such as penile prostheses and to their prevention and therapy.

Late onset endophthalmitis associated with intraocular lens: a case of molecularly proved S. epidermidis aetiology

A case of severe endophthalmitis after cataract extraction followed by posterior chamber lens implantation is reported. Microbiological cultures from a tap of the patient's aqueous humour prior to lens explantation as well as from the explanted lens and aqueous and vitreous humour during operation yielded Staphylococcus epidermidis sensu stricto. Scanning electron microscopy showed massive colonisation of the lens loop by staphylococci. Clonal identity of all isolates was demonstrated by plasmid DNA analysis and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) of extra-cellular products. This is strongly suggestive of the aetiological role of S. epidermidis in this case of late onset endophthalmitis.

Antimicrobial activity of polymers coated with iodine-complexed polyvinylpyrrolidone

Polymer-associated infection is a problem of increasing importance in modern medicine. In a new approach to prevent such infections we have modified polyvinylfluoride (TEDLAR) films by graft copolymerization with N-vinylpyrrolidone to which iodine can be complexed. Grafting reaction was performed by the preirradiation technique using an electron accelerator. Grafted films were then treated in Lugol's solution for at least 24 h. Release of free iodine from the films was determined either by titration or using the agar disc diffusion test, showing an iodine release for up to 4-5 days. The antimicrobial activity of the films was tested in bacterial adhesion measurements. Bacterial and fungal cells in the range of 10(3) to 10(6) cfu/cm2 polymer were found on control samples without iodine, whereas on iodine-complexed films no viable cells could be detected at least for 5 days or even longer. Thus, microbial adhesion and growth can be inhibited by iodine-containing polymers.

Ultrastructure of neutrophilic granulopoiesis in the bone marrow of patients with chronic myeloid leukemia (CML). A morphometric study with special emphasis on azurophil (primary) and specific (secondary) granules

In seven patients with chronic myeloid leukemia (CML) and ultrastructural and morphometric study was performed on neutrophilic granulopoiesis in bone marrow trephine biopsies. Bone marrow specimens from five patients without hematological abnormalities served as controls. In stable phases of CML, abnormalities of the maturing granulocytic lineage were most conspicuously expressed by an infrequently occurring nuclear disfiguration (blebs and disturbed bridging of segments). Morphometric evaluation included the numbers of azurphil (primary) and specific (secondary) granules, the cisternal length of the endoplasmic reticulum and the area of the mitochondrial profiles. These variables could be determined in early and late myeloblasts, promyelocytes, metamyelocytes, band cells and mature polymorphonuclear granulocytes. Statistical analysis with regard to control specimens demonstrated no significant differences in the total amount of neutrophil granules or of the other cell organelles.

Evidence for lectin-mediated adherence of S. saprophyticus and P. aeruginosa to polymers

By hemagglutination tests surface lectins on S. saprophyticus strain S 1 with N-acetylgalactosamine (GalNac) and N-acetylglucosamine (GlcNac) specificity and on P. aeruginosa ATCC strain 27853 with N-acetylneuraminic acid (NANA) specificity could be demonstrated. To elucidate the role of bacterial surface lectins for the specific adhesion, polyether urethane discs were preincubated for 15 h at 4 degrees C in human serum or urine. Adhesion studies with S. saprophyticus S1 and P. aeruginosa ATCC 27853 onto precoated polymers revealed that microbial lectins may play a role in the colonization of prosthetic devices since lectin-blocking with competitive glycoconjugates significantly decreased bacterial adherence to the coated surfaces. Non-specific carbohydrates did not inhibit the adherence demonstrating specificity of this process.

New concepts in the prevention of polymer-associated foreign body infections

Polymer-associated foreign body infections, especially those caused by coagulase negative staphylococci, have become a problem of increasing importance in modern medicine. Therapy of such infections is often difficult and requires in many cases the removal of a catheter or an implant. On the basis of polymer material modification alternative strategies for the prevention of foreign body infections are presented. By use of high energy radiation or glow discharge techniques polymers can be modified so that new chemical groups with potential antiadhesive or antimicrobial activities can be introduced to the polymer (surface). Another approach is the coupling or incorporation of antimicrobial agents (e.g. antibiotics) to or into polymers. Such polymer-antibiotic systems are obviously not able to prevent initial bacterial adhesion to the polymer material but can effectively eliminate already adherent bacteria from the polymer surface.

Bacterial adhesion to medical polymers--use of radiation techniques for the prevention of materials-associated infections

The basic principles of the adhesion of bacteria to polymer surfaces are discussed, as the first important step in the pathogenesis of foreign-body infections. Strategies for the prevention of foreign-body infections by polymer modification with ionizing radiation are presented. These include the modification of polymer surfaces by radiation or glow discharge techniques to obtain antiadhesive or antimicrobial surfaces, as well as the fixation or incorporation of antibiotic drugs to or into the polymer.

Characterization of the inner surface of tubular substrates by contact angle measurement

A new method for the direct measurement of the contact angle on the inner surface of tubular substrates is described. It is shown that the measured contact angles are in good accordance with those obtained on flat surfaces.

New aspects in the pathogenesis and prevention of polymer-associated foreign-body infections caused by coagulase-negative staphylococci

The significance of polymer-associated infections caused by coagulase-negative staphylococci is discussed. The aspects of bacterial adhesion to polymeric materials as the first important pathogenetic step in the development of such infections are treated. The role of extracellular slime substance (ESS) produced by the bacteria in the pathogenesis is elucidated and newer results concerning the interference of ESS with host defense mechanisms and antibiotic therapy are presented. As an approach to the prevention of polymer-associated foreign-body infections, the modification of the polymeric materials is introduced. Results of recent studies to achieve antiadhesive materials by radiation modification of polymers as well as the development of antimicrobial surfaces by incorporating or bonding antibiotics to polymers are presented.

Ultrastructure of megakaryocytes in the human bone marrow of patients with primary (essential) thrombocythemia

An ultrastructural study was performed on bone marrow specimens in 10 patients (5 males/5 females, median age 53 years) with primary (essential) thrombocythemia (PTH) and an excessive elevation of the platelet count (1,625 +/- 783 x 10(9)/l). In contrast to a not severely altered neutrophilic granulo- and erythrocytopoiesis, megakaryocytes showed conspicuous large to giant forms. These were characterized by a highly lobulated nucleus containing several nucleoli and an extensive intermediate zone of the cytoplasm with many Golgi fields, numerous profiles of the so-called demarcation membrane system and an abundance of alpha-granules and some dense bodies. Our results demonstrate that ultrastructure of the megakaryocytes in PTH does not reveal gross abnormalities, but features which are compatible with an enforced thrombocytogenetic activity in accordance with the excessively elevated platelet count. Similar changes have been described in animal experiments with induced thrombocytopenia and stimulation of platelet shedding. Evaluation of thrombocytogenesis suggests that it may be mediated by a process of fragmentation with partitioning of the extensive intermediate zone into numerous prospective platelet territories followed by segregation.

Typing of coagulase-negative staphylococci isolated from foreign body infections

Twenty-six coagulase-negative staphylococci isolated from patients with various foreign body infections were characterised using different typing systems. Staphylococcus epidermidis was the most predominant species found. Phage typability was below 50% in all strains. The strains showed differences in surface properties--relative hydrophobicity or hydrophilicity--and ability to adhere to polystyrene with subsequent slime production (adherence tube test). Protein and polypeptide profiles as well as plasmid profiles demonstrated the heterogeneity of the strains. Thus, this preliminary study indicates that all coagulase-negative staphylococci of human origin may become involved in foreign body infections.

Mechanisms and clinical relevance of bacterial adhesion to polymers

The mechanisms of bacterial adhesion to polymers with regard to their significance in the development of foreign-body infections are discussed. The morphological, physico-chemical and biological aspects are treated with special emphasis on the adhesion of coagulase-negative staphylococci to medical polymers. Strategies for the prevention of bacterial adhesion to biomaterials by developing antiadhesive polymers are given.

An immunohistochemical and electron microscopic study of extra-renal basement membranes in dogs with Samoyed hereditary glomerulopathy

Samoyed hereditary glomerulopathy (SHG) in dogs has been employed as a model for human hereditary nephritis (HN), since affected dogs and patients show splitting of glomerular capillary basement membranes by electron microscopy (EM) and absent staining of glomerular capillaries for Goodpasture antigen (GPA) by immunofluorescence (IF). EM and IF were used to examine basement membranes (BM) in skin, lung, choroid plexus, lens, retina, and inner ear in SHG. By EM, BM in these tissues appeared similar in affected male, carrier female, and unaffected dogs. By IF, GPA could be detected only in lens capsule, internal limiting membrane of retina and basilar membrane of inner ear of unaffected and carrier female dogs, but not in affected male dogs. However, eye abnormalities and hearing loss were not present in any dogs, in contrast to their frequent occurrence in human HN. Our findings on extra-renal BM in SHG suggest that GPA is not required to maintain normal vision or hearing in affected male dogs and permit a greater understanding of the pathogenesis of human HN.

Samoyed hereditary glomerulopathy: serial, clinical and laboratory (urine, serum biochemistry and hematology) studies

Human hereditary nephritis refers to familial glomerular diseases which may progress to renal failure. Samoyed hereditary glomerulopathy has been shown previously to be a model for hereditary nephritis. Clinical and laboratory studies were performed to follow progression to renal failure in 44 dogs in a family with Samoyed hereditary glomerulopathy. Affected males appeared healthy for their first three months but then became progressively wasted. Proteinuria was detected between two to three months of age; after five months, urine protein electrophoresis showed pre-albumin, albumin and alpha and beta globulin peaks. From three months onward, a reduced glomerular filtration rate was detected. Serum albumin decreased while amylase, urea, creatinine and phosphate increased from four to five months of age. Death from renal failure occurred by 15 months. Carrier females also became thinner and developed proteinuria between two and three months of age, but neither renal failure nor death ensured. Hence, SHG progressed rapidly in affected males but not in carrier females.

Samoyed hereditary glomerulopathy. Immunohistochemical staining of basement membranes of kidney for laminin, collagen type IV, fibronectin, and Goodpasture antigen, and correlation with electron microscopy of glomerular capillary basement membranes

Recent immunofluorescence studies on the kidneys of most males with hereditary nephritis have demonstrated an absence of Goodpasture antigen (GPA) from glomerular capillary basement membranes (GCBM). In the present study, we used immunofluorescence to determine whether laminin, collagen type IV, fibronectin, and GPA could be detected in basement membranes of the kidneys of dogs with Samoyed hereditary glomerulopathy, which was previously shown to be a model for human hereditary nephritis. The results obtained were correlated with the appearance of GCBM by electron microscopy (EM). The rabbit polyclonal antibodies used (antilaminin, anti-collagen type IV, and antifibronectin) showed specificity for the appropriate antigens in a plate-binding radioimmunoassay. Serum from a patient with Goodpasture syndrome was used to detect the GPA component of dog GCBM. Laminin and collagen type IV were present in GCBM, mesangium, tubular basement membrane, vascular basement membrane, and Bowman's capsule of neonatal, unaffected, and affected male and carrier female dogs. Fibronectin was present in mesangial, perivascular, and interstitial regions of the kidneys of all dogs and, in addition, in GCBM of neonatal, affected male, and carrier female dogs. GPA was not detected in the kidneys of neonatal dogs and its absence from GCBM correlated with their immature appearance by EM. However, a fully formed, trilaminar GCBM was observed by 3 weeks of age in unaffected, affected male, and carrier female dogs, before the detection of GPA in GCBM, which occurred at 4 weeks in unaffected and carrier female dogs, but still not in affected males. In the unaffected dogs, the presence of GPA correlated with the persistence of a fully formed trilaminar GCBM, which lasted throughout life, while in the carrier females, the presence of GPA correlated with focal areas of multilaminar splitting of GCBM by EM. In the affected male dogs, although a trilaminer GCBM was seen by 3 weeks of age, the persistent absence of GPA correlated with the eventual onset of multilaminar splitting of GCBM. These immunofluorescence and EM results suggest that GPA is not required to form a trilaminar GCBM initially but is necessary subsequently to maintain its integrity. GPA is normally present in the C terminal (NC1) domain of the collagen type IV molecule. It is hypothesized that Samoyed hereditary glomerulopathy in dogs and human hereditary nephritis result from a defect in the NC1 domain.

Chemical modification of polyurethanes by radiation-induced grafting

Basic methods of radiation-induced modification of polyurethanes for biomedical applications and of their characterization are briefly described. The most important works found in literature on radiation grafting of polyurethanes are discussed. The radiation grafting of polyetherurethane films and tubings by the preswelling method using various monomers and their physico-chemical characterization are discussed in detail with respect to the antithrombogenic properties of the materials. Novel applications for radiation-modified polyurethanes as drug delivery systems or antiinfectious materials are briefly mentioned.

Quantitation of anionic sites in glomerular capillary basement membranes of Samoyed dogs with hereditary glomerulopathy

Samoyed hereditary glomerulopathy (SHG) is an X-linked dominant disease characterized by proteinuria and renal failure in affected male dogs. Electron microscopic examination of glomerular capillary basement membranes (GCBM) shows widespread multilaminar splitting of the lamina densa, identical to that in Alport's syndrome. Anionic sites in GCBM of three affected males and five unaffected dogs were labeled using polyethyleneimine to determine whether proteinuria was associated with an alteration in their number. No significant differences were noted in the number of anionic sites in the lamina rara externa, whereas small but statistically significant increases were seen in the number of sites in the lamina rara interna of affected males. In the lamina densa, affected males showed a striking increase in anionic sites, particularly in regions of GCBM which were split. Thus, although proteinuria in some glomerular diseases has been attributed to a reduction in anionic sites in GCBM, this was not so in SHG.