Modification of central venous catheter polymers to prevent in vitro microbial colonisation

The efficacy of an antimicrobial catheter for the prevention of bacterial colonisation was investigated. The catheter was hydrophilic coated (Hydrocath) and impregnated with the quaternary ammonium antimicrobial agent, benzalkonium chloride (BZC). Microbial colonisation of this central venous catheter was compared to that of polyurethane catheters with or without a hydrophilic coating. Adherence of five strains ofStaphylococcus epidermidis to the three catheter types was determined with a microbial colonisation model. Adherence of three strains ofStaphylococcus epidermidis to Hydrocath catheters was significantly reduced in comparison to polyurethane catheters (p<0.01). BZC-impregnated Hydrocath catheters prevented bacterial colonisation of both the internal and external catheter surfaces (p<0.01). These results were confirmed by scanning electron microscopy. The findings demonstrate that hydrophilic-coated Hydrocath catheters can inhibit bacterial adherence in vitro. Bacterial colonisation was further restricted by the addition of BZC to these coated catheters.     

Adherence of staphylococci to intravascular catheters

Adherence of seven strains of Staphylococcus epidermidis and three strains of S. aureus to three types of intravascular catheters was assessed by ATP bioluminescence, by culture after ultrasonication and by scanning electronmicroscopy. The catheter materials studied were silicone elastomer, thermoplastic polyurethane and polyurethane coated with Hydromer, a coating which absorbs water and provides a hydrophilic sheath around the catheter. The adherence assays were performed in phosphate-buffered saline on a rotary shaker at 37 degrees C, with the catheters precoated with serum and uncoated, and the results were correlated with bacterial hydrophobicity. There was wide strain-to-strain variation in bacterial adherence; S. aureus and slime-producing S. epidermidis strains adhered better than did non-slime-producing strains. Overall, there was less bacterial adherence to Hydromer-coated catheters than to polyurethane and silicone catheters but it was unrelated to bacterial hydrophobicity. Serum coating of catheters resulted in marked reduction of bacterial adherence.     

Gentamicin-releasing urethral catheter for short-term catheterization

Urethral catheters, widely used for the drainage of the bladder, are associated with most urinary tract infections (UTIs) that account for 40% of all episodes occurring in acute-care hospitals. This study aimed to develop a gentamicin-releasing catheter that effectively prevents UTIs for short-term catheterization. For physical loading of gentamicin, the urethral catheters were coated by the simple dipping method with poly(ethylene-co-vinyl acetate) (EVA) and EVA/poly(ethylene oxide) (PEO) blends containing gentamicin. By varying the molecular weight (MW) and contents of PEO in the blends, various catheter surfaces were produced. In vitro drug release studies demonstrated that all the coated catheters exhibited sustained release up to 7 days; however, the release pattern was significantly dependant on the coating layers. Of the coated catheters, EVA/PEO (MW = 100k)-coated catheters were utilized to evaluate the antibacterial activity using an inhibition zone test, since they showed a promising drug release behavior and had PEO-rich biocompatible surfaces. In accordance with drug release behavior, EVA/PEO-coated catheters exhibited antibacterial activities for 7 days against Proteus vulgaris, Staphylococcus aureus and Staphylococcus epidermidis. These results imply that the catheters coated with EVA/PEO have a potential for short-term catheterization.     

银离子水凝胶涂层导尿管抑菌效力定量检查方法的建立

目的建立银离子水凝胶涂层导尿管的抑菌效力定量检查方法。方法根据《中华人民共和国药典》2015年版微生物计数法(四部通则1105),以金黄色葡萄球菌、铜绿假单胞菌、大肠埃希菌、表皮葡萄球菌和白色念珠菌作为试验菌株,以D/E中和肉汤作为中和剂,采用中和剂与薄膜过滤法联合使用的方式对银离子水凝胶涂层导尿管进行微生物计数方法适用性试验。根据《中华人民共和国药典》2015年版抑菌效力检查法(四部通则1121),采用经验证的微生物计数方法定量测定银离子水凝胶涂层导尿管对上述5种试验菌的抑菌效力。结果D/E中和肉汤与薄膜过滤法联合使用可以有效中和银离子的抑菌活性,银离子水凝胶涂层导尿管对上述5种试验菌均具有较好的抑菌作用,抑菌率均能达到99%,且抑菌效力可持续至14 d。结论采用D/E中和肉汤与薄膜过滤法联合使用的方式建立适用于银离子水凝胶涂层导尿管的微生物计数方法,可照此方法进行抑菌效力检查中存活菌数的测定。建立的方法可用于银离子水凝胶涂层导尿管抑菌效力的定量检查。     

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.     

Biological efficacy of electroless-deposited silver on plasma activated polyurethane

Silver coating of catheters has been shown to have inhibitory effects on bacterial growth and adhesion to catheter surfaces. In this study, plasma-modification was used to enhance the adhesion of an electroless silver coating on polyurethane. Both the antibacterial and antiadhesive properties of these coatings were investigated. Bacterial growth was inhibited in cultures exposed to silver-treated polyurethane compared to unmodified polyurethane. Higher growth inhibition was observed for polyurethane surfaces with lower silver coverage. Bacterial adhesion was completely inhibited on all silver-coated surfaces.     

Gentamicin-releasing urethral catheter for short-term catheterization

Urethral catheters, widely used for the drainage of the bladder, are associated with most urinary tract infections (UTIs) that account for 40% of all episodes occurring in acute-care hospitals. This study aimed to develop a gentamicin-releasing catheter that effectively prevents UTIs for short-term catheterization. For physical loading of gentamicin, the urethral catheters were coated by the simple dipping method with poly(ethylene-co-vinyl acetate) (EVA) and EVA/poly(ethylene oxide) (PEO) blends containing gentamicin. By varying the molecular weight (MW) and contents of PEO in the blends, various catheter surfaces were produced. In vitro drug release studies demonstrated that all the coated catheters exhibited sustained release up to 7 days; however, the release pattern was significantly dependant on the coating layers. Of the coated catheters, EVA/PEO (MW = 100k)-coated catheters were utilized to evaluate the antibacterial activity using an inhibition zone test, since they showed a promising drug release behavior and had PEO-rich biocompatible surfaces. In accordance with drug release behavior, EVA/PEO-coated catheters exhibited antibacterial activities for 7 days against Proteus vulgaris, Staphylococcus aureus and Staphylococcus epidermidis. These results imply that the catheters coated with EVA/PEO have a potential for short-term catheterization.     

Impact of chlorhexidine-silver sulfadiazine-impregnated central venous catheters on in vitro quantitation of catheter-associated bacteria.

To assess the impact of the antiseptic effects of silver sulfadiazine-chlorhexidine-impregnated central venous catheters on catheter culture systems, a series of in vitro experiments was performed. Segments of antiseptic and non-antiseptic-impregnated catheters were sonicated in thioglycolate broth and removed. After the addition of 10(3) CFU of Staphylococcus epidermidis per ml, aliquots of catheter-exposed broth were subcultured onto blood agar at 15-min intervals. Decreased mean colony counts were noted at 45 min for broth exposed to antiseptic-impregnated catheters compared with the colony counts for broth exposed to non-antiseptic-impregnated catheters (170 versus 540 CFU/ml). These effects, which were also demonstrated by the roll-plate method, were abrogated by the use of medium containing inhibitors of silver sulfadiazine and chlorhexidine. To assess the duration of the antiseptic effects, catheter segments were suspended for up to 14 days in phosphate-buffered saline, incubated with 10(6) CFU of S. epidermidis per ml, and cultured. Inhibition of bacterial growth by antiseptic-impregnated catheters disappeared after 14 days. These studies suggest that antiseptic compounds elute from catheters during broth- and solid medium-based culturing processes, making necessary the addition of inhibitors of these compounds in culture media. They further suggest that the antimicrobial effects of antiseptic-impregnated catheters wane within several days of placement.     

Examination of the morphology of bacteria adhering to peritoneal dialysis catheters by scanning and transmission electron microscopy.

We examined Tenckhoff peritoneal catheters by scanning and transmission electron microscopy to study the morphology of bacterial adherence. Two catheters were removed from uninfected patients, three from patients with exit site infections, four from patients with peritonitis, and one from a patient with both exit site infection and peritonitis. Infecting organisms included three of Staphylococcus aureus and one each of Enterobacter sp., Staphylococcus epidermidis, Achromobacter xylosoxidans, Serratia sp., Klebsiella sp., and Candida albicans. Considerable morphological variation in adherence to the peritoneal dialysis apparatus occurred. No inflammatory cells were ever seen in association with infected cuffs, only two of the five patients with peritonitis had inflammatory cells associated with their catheters. In both instances, these cells tended to occur in clumps and demonstrated no flattening when in contact with the surface. Colonization of the catheter was uneven--bacteria tended to occur in clusters. Extensive matrix formation was evident in several instances, and condensation of this matrix onto the bacteria during the dehydration process rendered clumps of bacterial cells amorphous at times. Bacteria were adherent to the subcutaneous cuff in those patients with exit site infections. Gram-negative bacteria attached to individual dacron fibers of the cuff, often several layers deep. Gram-positive bacteria tended to adhere in clusters.     

Bacterial adhesion on biomedical surfaces covered by micrometric silver Islands

A set of Cu-Mn-O and Ag-Cu-Mn-O films were sputter-deposited onto polished Ti-6Al-4V coupons and the microbiological adherence of Staphylococcus sp. was studied in these biomedical surfaces modified by using advanced ternary and quaternary oxides, these latter incorporated micrometric silver islands. Silver is known to have a natural biocidal character and its presence in the surface of Ti-6Al-4V forming large micrometric islands. In principle, predicted to enhance the antimicrobial properties of biomedical surfaces. Microbial adhesion tests were performed using collection strains and six clinical Staphylococcus aureus and Staphylococcus epidermidis strains. The adherence study was performed using a previously published protocol by Kinnari et al. Collection strains and clinical strains showed decreased adherence to modified materials; however, only on the clinical strains were there statistically significant differences between Cu-Mn-O and Ag-Cu-Mn-O containing silver islands. Nanocrystalline silver dissolves and releases both Ag(+) and Ag(0) whereas other silver sources release only Ag+. We can conclude that nanocrystalline silver coating, confirmed by XRD, appears to alter the biological properties of the solution, particularly antimicrobial activity.     

Modulation of adherence of coagulase-negative staphylococci to teflon catheters in vitro

The mechanism of adherence of Staphylococcus epidermidis to commercially available catheters was studied in vitro in a quantitative assay employing ³ H-labelled bacteria. It was found that adherence to Teflon catheters was significantly related to the degree of hydrophobicity of the strains. When hydrophobic groups were removed from Staphylococcus epidermidis by pepsin treatment, adhesion was almost completely abolished. Preincubation of catheters in human serum also caused a 80–90 % reduction of adherence. Preincubation of Staphylococcus epidermidis in serum similarly decreased adhesion. This effect of serum was mainly due to albumin, while IgG and fibronectin were less effective. Culture of Staphylococcus epidermidis in subinhibitory concentrations (0.5 MIC) of cephalothin, clindamycin and vancomycin resulted in a 30–80 % reduction in adhesion.     

Effect of plastic catheter material on bacterial adherence and viability

The kinetics of adherence of single isolates of Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa and Escherichia coli to catheters made of polyvinyl chloride (PVC), Teflon, siliconised latex, polyurethane and Vialon was evaluated by a radiometric assay. Radiolabelled bacteria (10(8) cfu/ml) were incubated in vials containing 1-cm lengths of catheter for up to 3 days. The peak of maximal adherence to each biomaterial was reached after 24 h for P. aeruginosa and after 72 h for the other strains. Bacterial adherence to PVC and siliconised latex was significantly higher (2-6 times; p less than 0.05) than to the other biomaterials for all the strains. The lowest values of adherence were observed with polyurethane and Vialon for the staphylococci but with Teflon for E. coli and P. aeruginosa. Bacterial viability and growth was evaluated in eluates obtained from incubation of segments of each catheter in buffer for 24 h. None of the eluates affected the viability of the staphylococci. However, all of them, significantly increased the growth of E. coli and P. aeruginosa with the exception of the eluate from siliconised latex, in which the inoculum count was reduced to an undetectable level for E. coli. We conclude that bacterial adherence to catheters may depend in part on the nature of the biomaterial and that certain substances eluted from the catheters may affect the viability and growth of different micro-organisms.     

Adherence of coagulase-negative staphylococci onto polyethylene catheters in vitro and in vivo: a study on the influence of various plasma proteins

Bacterial adherence on PE catheters inserted into the carotid artery of rabbits was assessed at 5, 30, and 240 min after injection with bacteria of five coagulase-negative staphylococci (CN Staph). These studies revealed that CN Staph adhere onto PE catheters 5 min after injection with bacteria. At 240 min after injection with bacteria almost all catheters were sterile, indicating that initially adherent bacteria on PE catheters disappear with time. EM studies revealed high numbers of platelets and leukocytes and many fibrin deposits on the surface of the PE catheter. In addition, the adherence of the five test strains on PE catheters was determined in vitro. In these in vitro studies the bacteria and catheters were pretreated with either fibrinogen, fibronectin, albumin or citrated whole plasma or the liquid adherence medium was supplemented with these proteins or the adherence assay was done in citrated whole plasma. The presence of proteins in the adherence medium or pretreatment of the catheter or bacteria with either fibronectin, albumin or whole citrated plasma markedly inhibited bacterial adherence. In contrast, pretreatment of bacteria or both bacteria and catheters with fibrinogen enhanced bacterial adherence suggesting the presence of ligands for fibrinogen on the cell surface of CN Staph.     

Vascular graft infections: in vitro and in vivo investigations of a new vascular graft with long-term protection

We investigated a polyester vascular prosthesis (PET) coated with elemental silver (SC). Measurement of silver release over a period of 52 weeks by means of inductively coupled plasma atomic emission spectrometry of PET with (PET-G) and without (PET-N) gelatine impregnation revealed a silver release on the first day of 1.2 +/- 0.2 microg (PET-N) and 1.2 +/- 0.1 microg (PET-G) (calculated for 1 g of prosthesis); from the 90th day onward, it was between 0.22 +/- 0.14 microg (PET-N) and 0.18 +/- 0.12 microg (PET-G) per day. The prostheses were incubated with Staphylococcus aureus (S.a.), Staphylococcus epidermidis (S.e.), or Escherichia coli (E.c.) to investigate in vitro antibacterial efficacy. After 6 h of incubation, no colony-forming units were to be seen for any of the bacterial suspensions for PET with SC (p < 0.001). To investigate in vivo antibacterial efficacy, PET-G rings with and without SC contaminated with S.a., S.e., or E.c. were implanted in 18 albino rabbits and examined 7 days after agar culture for 48 h. The silver coating was associated with a significant reduction in bacterial growth (S.a., p = 0.001; S.e., p < 0.005; E.c., p < 0.001). The silver-coated prosthesis, with and without gelatine impregnation, had a significantly antibacterial effect with continuous release of silver.     

Prevention of catheter related bloodstream infection by silver iontophoretic central venous catheters: a randomised controlled trial

AIM: To evaluate the efficacy of silver iontophoretic central venous catheters in preventing catheter related colonisation and bloodstream infection among high risk patients in a tertiary hospital. METHODS: Patients requiring central venous access for a period greater than seven days were stratified into two groups according to systemic inflammatory response syndrome criteria before being randomly assigned to receive either silver iontophoretic or control catheters. The incidence of catheter colonisation and catheter related bloodstream infection (CRBSI) was recorded. RESULTS: Three hundred and four single lumen study catheters were inserted into 268 patients. Total duration of catheterisation was 5449 days (median, 12 days/catheter). Complete data could be evaluated in 270 catheters: 128 silver iontophoretic catheters and 140 untreated catheters. Forty seven silver iontophoretic catheters (36.7%) were colonised compared with 48 control catheters (33.8%). Seven cases (5.5%) of CRBSI occurred in patients who received silver iontophoretic catheters, compared with 11 cases (7.7%) in patients receiving control catheters. There was no significant difference in the incidence of catheter colonisation or CRBSI between silver iontophoretic and control catheters. When the duration of catheter placement was taken into consideration, Kaplan-Meier analysis showed no significant difference in the risk of CRBSI between the silver iontophoretic catheters and the untreated catheters (p = 0.77). CONCLUSION: There was no significant difference in the incidence of catheter colonisation or CRBSI among high risk patients between silver iontophoretic catheters and control catheters. Future prospective, randomised studies with a larger number of catheters are encouraged to confirm or refute these results.     

Norfloxacin-releasing urethral catheter for long-term catheterization

Norfloxacin-releasing urethral catheters were prepared for the purpose of preventing urinary tract infections during long-term catheterization. The outer and inner surfaces of the catheters were coated with poly(ethylene-co-vinyl acetate) (EVA) and an amphiphilic multiblock co-polymer (PEO_2kPDMS), composed of poly(ethylene oxide) and poly(dimethyl siloxane). Norfloxacin, a fluoroquinolone synthetic antibiotic, was impregnated into a coating layer. The in vitro drug release behavior was monitored for 30 days, the surface topography was investigated using scanning electron microscopy (SEM) and the antibacterial activity against different bacteria implicated in urinary tract infection was evaluated by the in vitro inhibition zone test. All the coated catheters showed continuous delivery of norfloxacin for up to 30 days owing to hydrophobic natures of norfloxacin and EVA. PEO_2kPDMS incorporated in a coating layer produced a smooth and uniform surface. The coated catheters created considerable inhibition zones for 10 days against Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris, indicating the continuous release of norfloxacin. Overall, it was evident that the catheters coated with EVA/PEO_2kPDMS blends containing norfloxacin have a promising potential for the clinical use in patients undergoing long-term catheterization.     

In Vitro Zones of Inhibition of Coated Vascular Catheters Predict Efficacy in Preventing Catheter Infection with Staphylococcus aureus In Vivo

 This report summarizes data from 35 rabbit model experiments investigating the relationship between in vitro anti-infective catheter coating zones of inhibition and in vivo efficacy. The rabbit model studies involving 15 anti-infective coatings demonstrate an inverse correlation between the sizes of zones of inhibition of Staphylococcus aureus and both the quantity of Staphylococcus aureus removed from the catheter and the risk of a purulent infection. The review of seven previously published clinical trials reveals that the use of anti-infective coated catheters, efficacious in the rabbit model, was associated with a higher success rate than the use of uncoated catheters in preventing both Staphylococcus aureus catheter colonization (odds ratio: 1.28; 95% confidence interval: 0.84–1.93) and Staphylococcus aureus catheter-related bloodstream infection (odds ratio: 3.07; 95% confidence interval: 0.98–9.60) in humans. These findings strongly suggest a correlation between zones of inhibition and in vivo efficacy. In vitro zones of inhibition may serve as a useful screening test for evaluating new anti-infective coatings.     

Biofilm-Infected Intracerebroventricular Shunts Elicit Inflammation within the Central Nervous System

Central nervous system catheter infections are a serious complication in the treatment of hydrocephalus. These infections are commonly caused by Staphylococcus epidermidis and Staphylococcus aureus, both known to form biofilms on the catheter surface. Our objective was to generate a novel murine model of central nervous system catheter-associated biofilm infection using a clinical S. aureus isolate and characterize the nature of the inflammatory response during biofilm growth. Silicone catheters were precoated with S. aureus to facilitate bacterial attachment, whereupon infected or sterile catheters were stereotactically inserted into the lateral ventricle of the brain in C57BL/6 mice and evaluated at regular intervals through day 21 postinsertion. Animals tolerated the procedure well, with no clinical signs of illness or bacterial growth seen in the control group. Bacterial titers associated with central nervous system catheters were significantly elevated compared to those from the surrounding parenchyma, consistent with biofilm formation and minimal planktonic spread of infection. Catheter-associated bacterial burdens progressively increased, with maximal colonization achieved at day 7 postinfection. Analysis of inflammatory infiltrates by fluorescence-activated cell sorting (FACS) revealed significant macrophage and neutrophil influx, which peaked at days 3 and 5 to 7, respectively. In contrast, there were no detectable immune infiltrates associated with tissues surrounding sterile catheters. Biofilm infection led to significant increases in chemokine (CXCL1 and CCL2) and proinflammatory cytokine (interleukin 17 [IL-17]) expression in tissues surrounding infected central nervous system catheters. Based on these results, we propose this approach is a valid animal model for further investigations of catheter-associated central nervous system shunt infections.     

Development of an artificial dermis preparation capable of silver sulfadiazine release

This article describes the antibacterial effects of an artificial dermis impregnated with silver sulfadiazine (Ag-SD) in vitro as well as in vivo. In the in vitro test, silver release from the artificial dermis impregnated with Ag-SD, by immersion in collagenase solution was controlled by the degradation of the collagen sponge.The artificial dermis impregnated with 3% or higher doses of Ag-SD completely suppressed the growth of Pseudomonas aeruginosa (Ps.) or Staphylococcus aureus (St.). The cytotoxicity test revealed that impregnation of 5% or higher doses of Ag-SD suppressed the growth of fibroblasts. However, when the artificial dermis impregnated with Ag-SD was implanted into full-thickness skin defects on the backs of guinea pigs, no tissue damage was histologically observed around the implanted site of the dermis. In the in vivo test, the artificial dermis impregnated with 10% Ag-SD, which was grafted on experimentally contaminated wounds in the backs of guinea pigs, macroscopically suppressed degradation of the collagen sponge, and significantly reduced the growth of both Ps. and St., compared with artificial dermis without Ag-SD. We conclude that collagen sponge impregnated with Ag-SD is a promising artificial dermis applicable to treat contaminated wounds.     

Synthesis of sericin-conjugated silver nanoparticles and their potential antimicrobial activity

Nanoparticles (NPs) are being recognized as antibacterial agents due to their rapidly increasing multidrug resistance in bacterial pathogens. Hence, there is an unmet need to identify the natural antibacterial agent. The present study aimed to evaluate the antibacterial activity of sericin-conjugated silver NPs synthesized by using sericin as a reducing and capping agent. Synthesized NPs were characterized by scanning electron microscope, nanolaser particle size analyzer (BT-90), Fourier-transform infrared analysis, and energy-dispersive X-ray. The biogenic NPs significantly inhibited the growth of Escherichia coli (12–15 mm zone of inhibition), Staphylococcus aureus (14.6–15.4 mm zone of inhibition), and Klebsiella pneumoniae (12.5–18 mm zone of inhibition). The stability of naturally synthesized NPs was examined at various temperatures (i.e., 4°C, 37°C, and 55°C) and pH (i.e., 3, 7, and 11). Temperature variability did not significantly affect the efficacy of NPs. However, NPs performed better at higher pH levels. This study suggested that the sericin-based silver NPs are not only effective against bacteria, but they also maintain the stability at different ranges of temperature and pH. We concluded that the sericin-conjugated silver NPs possess the remarkable antibacterial potential, which suggests their large-scale use as a cheap and stable antimicrobial agent in the future.