B. Jansen

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 R 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.

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.

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.

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 Lugols 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 103 to 106 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.

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.

Antibiotic-Containing Polyurethanes for the Prevention of Foreign-Body Infections

The incorporation of antibiotics (clindamycin, flucloxacillin, vancomycin) into polyurethanes to obtain drug delivery devices is described. The drug release kinetics of the films was determined in a modified bioassay. Polyurethane films containing clindamycin or vancomycin show a high initial release rate, and drug release is observed up to 5–7 days. Flucloxacillin-containing polymer films exhibit a more constant drug release profile with a drug release lasting at least for 15 days or longer. Radiation methods as well as glow discharge techniques were applied to antibiotic-loaded films in order to modify drug release characteristics. Effectiveness of the devices to prevent adhesion or to kill adherent bacteria was tested with in vitro bacterial adhesion experiments. Initial adhesion to the antibiotic-loaded films is not prevented, but in case of clindamycin- and flucloxacillin-containing films a considerable reduction of adherent viable cells from 105 to 101 is observed.

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.

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.

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.

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.