Bernd Jansen

Detection of antibiotic‐resistant bacteria and their resistance genes in wastewater, surface water, and drinking water biofilms

Abstract In view of the increasing interest in the possible role played by hospital and municipal wastewater systems in the selection of antibiotic-resistant bacteria, biofilms were investigated using enterococci, staphylococci, Enterobacteriaceae, and heterotrophic bacteria as indicator organisms. In addition to wastewater, biofilms were also investigated in drinking water from river bank filtrate to estimate the occurrence of resistant bacteria and their resistance genes, thus indicating possible transfer from wastewater and surface water to the drinking water distribution network. Vancomycin-resistant enterococci were characterized by antibiograms, and the vanA resistance gene was detected by molecular biology methods, including PCR. The vanA gene was found not only in wastewater biofilms but also in drinking water biofilms in the absence of enterococci, indicating possible gene transfer to autochthonous drinking water bacteria. The mecA gene encoding methicillin resistance in staphylococci was detected in hospital wastewater biofilms but not in any other compartment. Enterobacterial ampC resistance genes encoding beta-lactamase activities were amplified by PCR from wastewater, surface water and drinking water biofilms.

Infections Associated with Medical Devices Pathogenesis, Management and Prophylaxis

The insertion or implantation of foreign bodies has become an indispensable part in almost all fields of medicine. However, medical devices are associated with a definitive risk of bacterial and fungal infections. Foreign body-related infections (FBRIs), particularly catheter-related infections, significantly contribute to the increasing problem of nosocomial infections. While a variety of microorganisms may be involved as pathogens, staphylococci account for the majority of FBRIs. Their ability to adhere to materials and to promote formation of a biofilm is the most important feature of their pathogenicity. This biofilm on the surface of colonised foreign bodies is regarded as the biological correlative for the clinical experience with FBRI, that is, that the host defence mechanisms often seem to be unable to handle the infection and, in particular, to eliminate the microorganisms from the infected device. Since antibacterial chemotherapy is also frequently not able to cure these infections despite the use of antibacterials with proven in vitro activity, removal of implanted devices is often inevitable and has been standard clinical practice. However, in specific circumstances, such as infections of implanted medical devices with coagulase-negative staphylococci, a trial of salvage of the device may be justified. All FBRIs should be treated with antibacterials to which the pathogens have been shown to be susceptible. In addition to systemic antibacterial therapy, an intraluminal application of antibacterial agents, referred to as the ‘antibiotic-lock’ technique, should be considered to circumvent the need for removal, especially in patients with implanted long-term catheters.To reduce the incidence of intravascular catheter-related bloodstream infections, specific guidelines comprising both technological and nontechnological strategies for prevention have been established. Quality assurance, continuing education, choice of the catheter insertion site, hand hygiene and aseptic techniques are aspects of particular interest. Furthermore, all steps in the pathogenesis of biofilm formation may represent targets against which prevention strategies may be directed. Alteration of the foreign body material surface may lead to a change in specific and nonspecific interactions with micro-organisms and, thus, to a reduced microbial adherence. Medical devices made out of a material that would be antiadhesive or at least colonisation resistant would be the most suitable candidates to avoid colonisation and subsequent infection. Another concept for the prevention of FBRIs involves the impregnation of devices with various substances such as antibacterials, antiseptics and/or metals. Finally, further studies are needed to translate the knowledge on the mechanisms of biofilm formation into applicable therapeutic and preventive strategies.

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.

Development of a long-lasting ventricular catheter impregnated with a combination of antibiotics

A ventricular silicone catheter impregnated with a combination of rifampin and a quinolone was developed in order to prevent ventricular shunt related infections. As model substance for the quinolones we used sparfloxacin, because of its specific physicochemical properties resulting in a quantitative detection also in the presence of a second antibiotic. In our study we focused especially on an optimization of the antibiotic release out of the impregnated catheters in order to develop long lasting devices with a broad antimicrobial spectrum. A release-optimized catheter was tested with an in vitro colonization test and additionally with a method developed to examine the spread of bacteria on a catheter surface. In vitro experiments showed that the impregnated catheters reduce the colonization with Staphylococcus epidermidis for at least 1 year and prevent the spread of bacteria along the catheter surface.

A silicone ventricular catheter coated with a combination of rifampin and trimethoprim for the prevention of catheter-related infections.

So-called antiinfective catheters which are generated by incorporation of antimicrobial substances into polymers appear to be effectful devices in the prevention of catheter related infections. Such devices mainly act by prevention of bacterial colonization of the catheter surface rather than by inhibition of adherence. In a preceding study, we developed a rifampin-containing silicone catheter for the prevention of ventricular shunt infection. In the present study, this work was continued with a combination of antimicrobials incorporated in silicone ventricular catheters to reduce the risk of rifampin resistance and to expand the antimicrobial spectrum. We found that the drug release kinetics could be greatly influenced by the incorporation conditions. It was possible to incorporate an optimal antibiotic combination of rifampin and trimethoprim into the polymer resulting in defined release rates and a defined total release. A catheter loaded with this combination showed an excellent reduction of the colonization with Staphylococcus aureus (99.97% reduction within 3 hours) under in-vitro conditions.

In vitro efficacy of a Hydrophilic Central Venous Catheter Loaded with Silver to Prevent Microbial Colonization

A method was developed to load the surface of a central venous catheter with silver to prevent bacterial colonization. Silver confers a broad antimicrobial activity with a relatively low risk of resistance. Catheters were incubated with a silver nitrate solution in different concentrations. The solvent, incubation temperature and incubation period were varied to examine the influence on the catheter loading. With increasing incubation temperature, time and concentration of silver nitrate, higher rates of silver elution were observed by atomic absorption spectroscopy. Furthermore, by using ethanol-water as a solvent instead of pure water, the amount of silver bound to the catheter surface was enhanced. The release of silver from the catheter surface is mainly controlled by first order kinetics. Antimicrobial efficacy of the modified catheter, in comparison to unloaded catheters, was tested in a stationary and a dynamic model with different microorganisms. Adherence experiments with Candida albicans showed almost complete inhibition of growth during a period of 72 hours, including initial adherence. While initial adherence of bacteria could not be prevented, these experiments showed an excellent reduction of bacterial colonization. In a perfusion model, adhesion of E. coli could be reduced for at least seven days. Further studies are planned to examine prolonged antimicrobial effects.

Antimicrobial efficacy and optimized cell adhesion from defined plasma polymerised multilayer structures involving zinc acetylacetonate and allylamine

Plasma polymer-based zinc release systems combined with a biocompatible surface layer are discussed, which together allow for optimum antimicrobial properties towards pathogenic bacteria such as Staphylococcus aureus while at the same time show excellent cytocompatibility and biocompatibility. The surfaces developed consist of a multilayer system in which each layer exhibits a particular function. The antimicrobial layer shows a burst release of zinc within approximately 24 hours. A top-coating of plasma polymerised allylamine acts as a barrier layer that reduces the diffusion of zinc out of the layers for up to 2 weeks and at the same time induces cytocompatibility. The properties of the deposits were analysed using InfraRed Reflection Absorption Spectroscopy (IRRAS), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), cell culturing and different bacterial assays. A structure was developed that showed antimicrobial efficacy towards Methicillin Susceptible Staphylococcus aureus (MSSA), while at the same time human endothelial cells (HUVECs) and fibroblast readily adhered to the surface. Antimicrobial properties could be tuned to last from a few days to two weeks, which corresponds to a typical time frame required to reduce the risk of infection in postoperative wounds.

Changing Material Surface Chemistry for Preventing Bacterial Adhesion

Since the initial step in the pathogenesis of catheter related infections is the adhesion of bacteria to the polymer, prevention of bacterial adherence should be an ideal way to avoid foreign body infections.21 A scientific understanding of the interactions between microorganisms and commonly used polymers is the basis of any effective development of devices with antiinfective surfaces. Thus Ferreiros et al. studied the in vitro adhesion of twenty nine Staphylococcus epidermidis strains to Teflon, polyethylene and polycarbonate.11 It was found that all strains showed a high adhesion to polymers with a high surface free energy. Reid et al. investigated the adhesion of microorganisms to urinary catheter surfaces.40 They found Lactobacillus acidophilus adhesion correlated with substratum surface tension, whereas adherence of a S. epidermidis strain did not. Escherichia coli adhered very poorly to all polymers tested. A correlation between surface tension of different synthetic polymers used for medical purposes and staphylococci was also observed in a study conducted by us:33 bacterial attachment decreased with increasing surface tension of synthetic materials.

Prophylaxe gegen Infektionen durch Streptococcus pneumoniae

ZusammenfassungStreptococcus pneumoniae steht als Erreger ambulant erworbener Pneumonien an erster Stelle. Vor allem bei Patienten mit verminderter Immunantwort werden invasive Pneumokokkeninfektionen als besonders risikoreich eingestuft und gehen mit einer hohen Mortalität einher.Weltweit wird eine zunehmende Antibiotikaresistenz von Streptococcus pneumoniaebeobachtet. Daher hat die Ständige Impfkommission (STIKO) die Impfung für Risikogruppen in ihre aktuellen offiziellen Empfehlungen vom März 1998 aufgenommen. Der bereits seit längerem kommerziell verfügbare 23-valente Polysaccharidimpfstoff vermittelt bei Kindern ab dem zweiten Lebensjahr und Erwachsenen eine gute Immunantwort zur Abwehr von Pneumokokkeninfektionen. Er sollte in der Praxis mehr Beachtung finden.AbstractStreptococcus pneumoniae is the most common etiologic agent in outpatients pneumonia. Pneumococcal infections are often associated with high mortality risk in immunocompromised patients.An increasing resistance of Streptococcus pneumoniae to antibiotics is observed worldwide. This led to the official recommendation by the STIKO to use the vaccination in special risk groups. The commercially available 23-valent polysaccharide vaccine produces a reliable immune response against pneumococcal infection in children aged over 2 years and adults. The recommendation should be more realized in practice.

AKTUELLE EMPFEHLUNGEN ZUR PNEUMOKOKKEN-IMPFUNG

Bei den ambulant erworbenen Pneumonien steht Streptococcus pneumoniae als Erreger an erster Stelle. Gerade bei Patienten mit verminderter Immunantwort werden invasive Pneumokokkeninfektionen als risikoreich eingestuft und sind mit einer hohen Mortalität vergesellschaftet. Der seit längerem kommerziell verfügbare 23-valente Polysaccharid-Impfstoff vermittelt bei Kindern ab dem zweiten Lebensjahr und Erwachsenen eine gute Immunantwort zur Abwehr von Pneumokokkeninfektionen. Dies hat dazu geführt, daß die Ständige Impfkommission (STIKO) die Impfung für Risikogruppen in ihre aktuellen offiziellen Empfehlungen vom März 1998 aufgenommen hat.