Effects of Hydrogel/Silver Coatings on In Vitro Adhesion to Catheters of Bacteria Associated with Urinary Tract Infections

Sections of sterile all-silicone-, hydrogel/silver-all-silicone-, and hydrogel/silver-latex-Foley urinary catheters were exposed to suspensions of bacteria and Candida albicans associated with urinary tract infections. The adhesion of these microorganisms to the catheters was determined with a radiolabel–cell procedure and scanning electron microscopy. Anomalous data with the radiolabel procedure were produced with the hydrogel/silver-latex catheters for certain species. These aberrant data were related to adhesion on the untreated cut ends of the latex catheter. Radiolabel-cell-adhesion procedures that involve sections of coated materials may need to be supplemented with additional procedures such as scanning electron microscopy for valid interpretations of the data. Adhesion to the hydrogel/silver catheters by both Gram-positive- and Gram-negative bacteria most commonly associated with nosocomial urinary tract infections, including a strain of Pseudomonas aeruginosa noted for its superior adhesion capacity, was significantly lower than the adhesion to the control all-silicone catheter. Received: 21 January 2000 / Accepted: 26 February 2000     

Effect of the adhesive antibiotic TA on adhesion and initial growth of E. coli on silicone rubber

Catheter-associated urinary tract infection is the most common nosocomial infection, and contributes to patient morbidity and mortality. We investigated the effect that the TA adhesive antibiotic had on adhesion and initial growth in urine of Escherichia coli on silicone rubber. The TA antibiotic had reduced adhesion, and inhibited initial growth of the bacteria on the surface. Since adhesion and initial growth on the surface are an essential part of biofilm formation and subsequent infection, we speculate that the TA antibiotic coating might decrease the infection rate associated with indwelling urinary catheter.     

In Vitro Evaluation of the Efficacy of a Silver-Coated Catheter

Bacteria commonly associated with nosocomial urinary tract infections were examined in vitro for their relative adherence to latex, 100% silicone-, hydrogel-coated latex-, and hydrogel/silver-coated latex urinary catheters. Degrees of adherence within 2 h were determined with cells radiolabeled with leucine. Adherence was greatest and equivalent on silicone and latex catheters. Adherence of four strains of Escherichia coli to the hydrogel/silver-coated catheter was decreased by 50% to 99% in comparison with the other catheters. Repeat testing with strains of E. coli and Pseudomonas aeruginosa with over 50 catheters demonstrated a consistency in the inhibition. The hydrophilic coating of the catheter appeared to be primary in the decreased adherence phenomenon followed by a secondary biocidal effect of the silver ion. Received: 2 December 1995 / Accepted: 3 January 1996     

Antibacterial activity of plastics coated with silver-doped organic-inorganic hybrid coatings prepared by sol-gel processes

Silver-doped organic-inorganic hybrid coatings were prepared starting from tetraethoxysilane- and triethoxysilane-terminated poly(ethylene glycol)-block-polyethylene by the sol-gel process. They were applied as a thin layer (0.6-1.1 microm) to polyethylene (PE) and poly(vinyl chloride) (PVC) films and the antibacterial activity of the coated films was tested against Gram-negative (Escherichia coli ATCC 25922) and Gram-positive (Staphylococcus aureus ATCC 6538) bacteria. The effect of several factors (such as organic-inorganic ratio, type of catalyst, time of post-curing, silver ion concentration, etc.) was investigated. Measurements at different contact times showed a rapid decrease of the viable count for both tested strains. The highest antibacterial activity [more than 6 log reduction within 6 h starting from 106 colony-forming units (cfu) mL-1] was obtained for samples with an organic-inorganic weight ratio of 80:20 and 5 wt % silver salt with respect to the coating. For the coatings prepared by an acid-catalyzed process, a high level of permanence of the antibacterial activity of the coated films was demonstrated by repeatedly washing the samples in warm water or by immersion in physiological saline solution at 37 degrees C for 3 days. The release of silver ions per square meter of coating is very similar to that previously observed for polyamides filled with metallic silver nanoparticles; however, when compared on the basis of Ag content, the concentration of silver ions released from the coating is much higher than that released from 1 mm thick specimens of polyamide (PA) filled with silver nanoparticles. Transparency and good adhesion of the coating to PE and PVC plastic substrates without any previous surface treatment are further interesting features.     

Novel Insights into the Proteus mirabilis Crystalline Biofilm Using Real-Time Imaging

The long-term use of indwelling catheters results in a high risk from urinary tract infections (UTI) and blockage. Blockages often occur from crystalline deposits, formed as the pH rises due to the action of urease-producing bacteria; the most commonly found species being Proteus mirabilis. These crystalline biofilms have been found to develop on all catheter materials with P. mirabilis attaching to all surfaces and forming encrustations. Previous studies have mainly relied on electron microscopy to describe this process but there remains a lack of understanding into the stages of biofilm formation. Using an advanced light microscopy technique, episcopic differential interference contrast (EDIC) microscopy combined with epifluorescence (EF), we describe a non-destructive, non-contact, real-time imaging method used to track all stages of biofilm development from initial single cell attachment to complex crystalline biofilm formation. Using a simple six-well plate system, attachment of P. mirabilis (in artificial urine) to sections of silicone and hydrogel latex catheters was tracked over time (up to 24 days). Using EDIC and EF we show how initial attachment occurred in less than 1 h following exposure to P. mirabilis. This was rapidly followed by an accumulation of an additional material (indicated to be carbohydrate based using lectin staining) and the presence of highly elongated, motile cells. After 24 h exposure, a layer developed above this conditioning film and within 4 days the entire surface (of both catheter materials) was covered with diffuse crystalline deposits with defined crystals embedded. Using three-dimensional image reconstruction software, cells of P. mirabilis were seen covering the crystal surfaces. EDIC microscopy could resolve these four components of the complex crystalline biofilm and the close relationship between P. mirabilis and the crystals. This real-time imaging technique permits study of this complex biofilm development with no risk of artefacts due to sample manipulation. A full understanding of the stages and components involved in crystalline encrustation formation will aid in the development of new protocols to manage and ultimately prevent catheter blockage.     

Antibacterial and antibiofilm effects of silver nanoparticles against the uropathogen Escherichia coli U12

The drug-resistant bacterial strains' emergence increases day by day. This may be a result of biofilm presence, which protects bacteria from antimicrobial agents. Thus, new approaches must be used to control biofilm-related infections in healthcare settings. In such a study, biological silver nanoparticles were introduced in such a study as an anti-biofilm agent against multidrug-resistant E. coli U12 on urinary catheters. Seven different silver nanoparticles concentrations were tested for their antimicrobial activities. Also, anti-biofilm activities against E. coli U12 were tested. Using the dilution method, the silver nanoparticles concentration of 85 μg/ml was the MIC (Minimum Inhibitory Concentration) that had excellent biocompatibility and showed significant antibacterial activity against E. coli U12. Scanning electron microscopy (SEM) confirmed that the highest efficient dose of silver nanoparticles was 340 μg/ml at 144 h that reduced adhesion of E. coli U12 to the urinary catheter. E. coli U12 cells ruptured cell walls and cell membranes after being examined using transmission electron microscopy (TEM). Thus, biologically prepared silver nanoparticles could be used to coat medical devices since it is effective and promising to inhibit biofilm formation by impregnating urinary catheters with silver nanoparticles.     

Uropathogenic Escherichia coli adhere to urinary catheters without using fimbriae

Abstract Five well-characterized urinary and fecal isolates of Escherichia coli were found to be hydrophilic irrespective of their serotypes and their ability to express fimbriae. All the strains were able to adhere to silicone latex urinary catheters, although strain 917, which expressed type P fimbriae as its only adhesin, adhered poorly. Although specific adhesins, particularly fimbriae, have been shown to mediate adhesion of E. coli to uroepithelial cells, they do not mediate specific adhesion onto urinary catheter material. The overall surfaces of the strains, tested using microelectrophoresis as a function of pH and X-ray photoelectron spectroscopy, were not significantly different, thus suggesting more non-specific adhesion mechanisms to urinary catheters.     

钛合金和钴铬合金表面白色念珠菌粘附的研究

目的比较钛合金(Ti-6Al-4V)和钴铬合金(Chromium-Cobaltalloy)表面白色念珠菌粘附能力的大小,研究表面粗糙度与细菌粘附的关系。方法将不同表面粗糙度的钛合金和钴铬合金试件进行白色念珠菌体外粘附试验,采用菌落形成计数法测定试件表面的细菌粘附量。结果各钛合金试件组的细菌粘附量均少于相同表面粗糙度的钴铬合金试件组,两种金属试件表面的细菌粘附量均随表面粗糙度的增大而增加。结论钛合金较钴铬合金更能减少由白色念珠菌引起的义齿性口炎等并发症,同时修复体表面严格的研磨抛光也能有效减少这些并发症。     

Early development of bacterial community diversity in emergently placed urinary catheters

ABSTRACT: BACKGROUND: Approximately 25% of hospitalized patients have a urinary catheter, and catheter associated urinary tract infection is the most common nosocomial infection in the US, causing >1 million cases/year. However, the natural history of the biofilms that rapidly form on urinary catheters and lead to infection is not well described. FINDINGS: We characterized the dynamics of catheter colonization among catheters collected from 3 women and 5 men in a trauma burn unit with different indwelling times using TRFLP and culture. All patients received antibiotic therapy. Results: Colony-forming units increased along the extraluminal catheter surface from the catheter balloon to the urethra, but no trend was apparent for the intraluminal surface. This suggests extraluminal bacteria come from periurethral communities while intraluminal bacteria are introduced via the catheter or already inhabit the urine/bladder. Richness of operational taxonomic units (OTUs) increased over time on the intraluminal surface, but was constant extraluminally. CONCLUSIONS: OTU community composition was explained best by time rather than axial location or surface. Our results suggest that catheter colonization can be very dynamic, and possibly have a predictable succession.     

Evaluation of the Adherence of Candida Species to Urinary Catheters

Catheter-associated urinary tract infections (CAUTIs) are the most common kind of nosocomial infection. Recent years have seen a significant increase in numbers of infections caused by yeasts of the genus Candida. The adherence of a microorganism to the host surface is a decisive factor in the success of colonization and the pathogenesis of infection. The objective of this work was to evaluate the adherence of species of the genus Candida to urinary catheters. In vitro adherence to the sections of latex and silicon catheters of Candida albicans and Candida parapsilosis were studied. Adherence was measured by counting the number of adhering viable cells and the results were expressed as Colonies Forming Units per mL. The results demonstrated that the latex catheter facilitated adherence more than the silicon catheter (p < 0.01). The adherence of the C. albicans was significantly greater than C. parapsilosis on latex, but it was similar on silicon.     

Increased endothelial cell adhesion on plasma modified nanostructured polymeric and metallic surfaces for vascular stent applications

Techniques to regenerate the vasculature have risen considerably over the last few decades due to the increased clinical diagnosis of artery narrowing and blood vessel blockage. Although initially re‐establishing blood flow, current small diameter vascular regenerative materials often eventually cause thrombosis and restenosis due to a lack of initial endothelial cell coverage on such materials. The objective of this in vitro study was to evaluate commonly used vascular materials (specifically, polyethylene terephthalate, polytetrafluoroethylene, polyvinyl chloride, polyurethane, nylon, commercially pure titanium, and a titanium alloy (Ti6Al4V)) modified using an ionic plasma deposition (IPD) process and a nitrogen ion implantation plasma deposition (NIIPD) process. Such surface modifications have been previously shown to create nanostructured surface features which mimic the natural nanostructured surface features of blood vessels. The modified and unmodified surfaces were characterized by scanning electron microscopy, atomic force microscopy and surface energy measurements. Furthermore, in vitro endothelial cell adhesion tests (a key first step for vascular material endothelialization) demonstrated increased endothelial cell adhesion on many modified (with IPD and NIIPD + IPD) compared to unmodified samples. In general, endothelial cell adhesion increased with nanoroughness and surface energy but demonstrated a decreased endothelial cell adhesion trend after an optimal coating surface energy value was reached. Thus, results from this study provided materials and a versatile surface modification process that can potentially increase endothelialization faster than current unmodified (conventional) polymer and metallic vascular materials. Biotechnol. Bioeng. 2009;103: 459–471. © 2009 Wiley Periodicals, Inc.     

Substrate-independent approach for the generation of functional protein resistant surfaces

A new route for coating various substrates with antifouling polymer layers was developed. It consisted in deposition of an amino-rich adhesion layer by means of RF magnetron sputtering of Nylon 6,6 followed by the well-controlled, surface-initiated atom transfer radical polymerization of antifouling polymer brushes initiated by bromoisobutyrate covalently attached to amino groups present in the adhesion layer. Polymer brushes of hydroxy- and methoxy-capped oligoethyleneglycol methacrylate and carboxybetaine acrylamide were grafted from bromoisobutyrate initiator attached to a 15 nm thick amino-rich adhesion layer deposited on gold, silicon, polypropylene, and titanium-aluminum-vanadium alloy surfaces. Well-controlled polymerization kinetics made it possible to control the thickness of the brushes at a nanometer scale. Zero fouling from single protein solutions and a reduction of more than 90% in the fouling from blood plasma observed on the uncoated surfaces was achieved. The feasibility of functionalization with bioactive compounds was tested by covalent attachment of streptavidin onto poly(oligoethylene glycol methacrylate) brush and subsequent immobilization of model antibodies and oligonucleotides. The procedure is nondestructive and does not require any chemical preactivation or the presence of reactive groups on the substrate surface. Contrary to current antifouling modifications, the developed coating can be built on various classes of substrates and preserves its antifouling properties even in undiluted blood plasma. The new technique might be used for fabrication of biotechnological and biomedical devices with tailor-made functions that will not be impaired by fouling from ambient biological media.     

Comparison of adhesion of the food spoilage bacterium Shewanella putrefaciens to stainless steel and silver surfaces

AIMS: To compare the number of attached Shewanella putrefaciens on stainless steel with different silver surfaces, thus evaluating whether silver surfaces could contribute to a higher hygienic status in the food industry. METHODS AND RESULTS: Bacterial adhesion to three types of silver surface (new silver, tarnished silver and sulphide-treated silver) was compared with adhesion to stainless steel (AISI 316) using the Malthus indirect conductance method to estimate the number of cfu cm(-2). The number of attached bacteria on new silver surfaces was lower than on steel for samples taken after 24 h. However, this was not statistically significant (P > 0.05). The numbers of attached bacteria were consistently lower when tarnished silver surfaces were compared with stainless steel and some, but not all, experiments showed statistical significance (P < 0.05). Treating new silver with sulphide to reproduce a tarnished silver surface did not result in a similar lowering of adhering cells when compared with steel (P > 0.05). CONCLUSIONS: New or tarnished silver surfaces caused a slight reduction in numbers of attached bacteria; however, the difference was only sometimes statistically significant. SIGNIFICANCE AND IMPACT OF THE STUDY: The lack of reproducibility in differences in numbers adhering to the different surfaces and lack of statistical significance between numbers of adhered viable bacteria do not indicate that the tested silver surfaces can be used to improve hygienic characteristics of surfaces in the food industry.     

双歧杆菌及表面分子对胃粘膜糖蛋白的粘附作用

目的：研究双歧杆菌及表面分子脂磷壁酸（Ｌｉｐｏｔｅｉｃｈｏｉｃ ａｃｉｄ,ＬＴＡ）、完整肽聚粮（Ｗｈｏｌｅ ｐｅｐ－ｔｉ－ｄｏｇｌｙｃａｎ ＷＰＧ）、多糖（Ｐｏｌｙｓａｃｃｈａｒｉｄｅ,ＰＳ）对猪胃粘膜糖蛋白的粘附作用。方法 采用ＥＬＩＳＡ阻断法测定了全菌不同菌液浓度的粘附作用。结果 表明ＬＴＡ、ＷＰＧ的粘附作用明显,ＰＳ粘附作用很弱。粘附随着菌液浓度的增高而增强。结论 在双歧杆菌的定植粘附机理中     

Adhesion of oral streptococci from a flowing suspension to uncoated and albumin-coated surfaces

A flow cell system was developed which allowed the study of bacterial adhesion to solid substrata at well-defined shear rates. In addition, the system enabled the solid surfaces to be coated with a proteinaceous film under exactly the same shear conditions. In this flow cell system, adhesion of three strains of oral streptococci from a phosphate-buffered solution onto three different substrata was studied as a function of time in the absence and presence of a bovine serum albumin (BSA) coating at a shear rate of 21 s-1. To obtain a wide range in surface free energies (gamma) representative strains (gamma b 38-117 mJ m-2) and solid substrata (gamma s 20-109 mJ m-2) were selected. The number of bacteria adhering was counted microscopically. In the absence of a BSA coating a linear relation was found between the number of bacteria adhering at saturation (nb,s) and the calculated interfacial free energy of adhesion (delta Fadh) for each of the three strains. In the presence of a BSA coating the number of bacteria adhering was greatly decreased in all cases. However, despite the presence of the BSA coating there was still a linear relation between the number of bacteria adhering at saturation and the interfacial free energy of adhesion, calculated on the basis of the surface free energy of the uncoated substrata. It can be concluded that the bare, uncoated substratum still influenced bacterial adhesion in spite of the marked influence of a BSA coating.     

Understanding urinary conditioning film components on ureteral stents: profiling protein components and evaluating their role in bacterial colonization

Ureteral stents are fraught with problems. A conditioning film attaches to the stent surface within hours of implantation; however, differences between stent types and their role in promoting encrustation and bacterial adhesion and colonization remain to be elucidated. The present work shows that the most common components do not differ between stent types or patients with the same indwelling stent, and contain components that may drive stent encrustation. Furthermore, unlike what was previously thought, the presence of a conditioning film does not increase bacterial adhesion and colonization of stents by uropathogens. Genitourinary cytokeratins are implicated in playing a significant role in conditioning film formation. Overall, stent biomaterial design to date has been unsuccessful in discovering an ideal coating to prevent encrustation and bacterial adhesion. This current study elucidates a more global understanding of urinary conditioning film components. It also supports specific focus on the importance of physical characteristics of the stent and how they can prevent encrustation and bacterial adhesion.     

Structural investigation of biological material in aqueous environment by means of infrared-ATR spectroscopy

Infrared attenuated total reflection (ATR) spectroscopy may be used to investigate biological material (e.g., membranes, proteins, erythrocytes etc.) under biological conditions provided that adhesion of the sample can be achieved in aqueous environment. Uncharged lipid multilayer model membranes can be attached by hydrophobic interaction when hydrophobic internal reflection plates (e.g., ZnSe, CdTe) are used. However, if an electric field is applied across the membrane, germanium reflection elements would be preferred because of their low electric resistance (approximately 50 omega cm). This material can also be used if cells or proteins are linked chemically to the ATR plate because of the hydrophilic surface which is similar to that of glass and, thus, enables chemical modification by silanization. It has turned out that good adhesion of uncharged and negatively charged model membranes to germanium plates is achieved when they are coated with a monomolecular layer of aminopropylsilane. There is some evidence that erythrocytes remain more stable when adsorbed to a polymerized aminosilane coating (organic silanization) rather than to the corresponding monolayer (aqueous silanization). Negatively charged germanium surfaces have been obtained by succinylation of the aminosilane coating. Furthermore it has been demonstrated that proteins can be bound to the aminosilane coating by means of carbodiimide. Immobilized acetylcholinesterase was still enzymatically active.     

The role of exopolymers in the attachment of sphingomonas paucimobilis

The importance of exopolymers in the adhesion of Sphingomonas paucimobilis was established by studying the attachment to glass of three mutants with defective gellan production. The attachment assays were performed in either phosphate buffered saline (controls) or in the exopolymeric solutions produced by the mutants. The exopolymer was found to have surface active properties, changing the glass surface from hydrophilic to hydrophobic, making adhesion thermodynamically favourable. Only the cells that had a substantial polymeric layer surrounding their walls were able to significantly colonise glass coated with the exopolymer. It is hypothesised that the exopolymer bound to the glass and the exopolymer present at the surface of the bacteria bound together, overcoming the energy barrier created by the negative charge of both surfaces. It is concluded that the exopolymer from S. paucimobilis has a dual role in the process of adhesion by both coating the surface thereby strengthening adhesion and by enhancing adhesion through the establishment of polymeric bridges.     

细菌影响泌尿系结石形成的作用机制及其化学基础

人体内影响泌尿系结石形成的细菌有2类：一类诱发尿石形成,主要是通过分解尿素使尿液pH升高、加重尿路感染、降低尿石抑制剂浓度、破坏尿路粘膜酸性粘多糖保护层从而促进晶体滞留;另一类抑制尿石的形成,这些细菌（主要为食草酸杆菌、乳酸杆菌和粪肠球菌等草酸分解菌）参与外源性草酸代谢,降低尿草酸浓度。探讨了该领域所面临的问题和将来的发展方向。     

纳米结构Ti/TiN涂层对NiTi合金生物相容性的影响

目的：评价纳米结构Ti/TiN涂层对镍钛形状记忆合金（含镍50.6at%）生物相容性的影响,为生物医用纳米结构Ti/TiN涂层表面改性的NiTi合金材料生物安全性提供依据。方法：不影响基体的形状记忆性或超弹性效应的前提下,采用真空过滤电弧离子镀技术,在NiTi合金表面沉积一层纳米结构Ti/TiN涂层,分别对表面改性前和改性后的NiTi合金样品进行体外细胞毒性实验、溶血实验和血小板粘附实验,探索纳米结构Ti/TiN涂层对NiTi合金生物相容性的影响。结果：表面具有纳米结构Ti/TiN涂层的NiTi合金无细胞毒性,H9C2（2-1）细胞相容性优于涂层前,细胞形态典型,粘附数量明显大于涂层前。纳米结构Ti/TiN涂层有改善NiTi合金的血液相容性作用,其溶血率从2.1%降至涂层改性后的1.2%,同时,血小板黏附量和聚集程度小于处理前的NiTi合金。结论：纳米Ti/TiN涂层能够显著改善NiTi合金的生物相容性。