Decreased bacterial adherence and biofilm formation on chlorhexidine and silver sulfadiazine-impregnated central venous catheters implanted in swine

Clinical experience with a chlorhexidine-coated PICC: A prospective, multicenter, observational study

INTRODUCTION

This study evaluated a chlorhexidine-coated peripherally inserted central catheter (PICC) and the incidence of associated complications within both inpatient and outpatient populations.

METHODS

This IRB-approved, multicenter, prospective observational study was performed at three large teaching hospitals in the US. All adults who required a PICC for ⩾14 days were considered. Patients were monitored throughout entire catheter dwell. Duplex venous ultrasounds were performed before insertion, after 10 to 14 days of dwell time, and upon removal. Data was collected from the hospital, outpatient clinic, and patient PICC diary records.

RESULTS

A total of 103 patients, 56% male, with mean BMI 29 ± 8.8, were enrolled. The majority (79%) of patients were from high-risk groups-cancer, infectious diseases, transplant, and trauma. Primary treatment indications were antibiotics (66.99%) and chemotherapy (25.24%). Double lumen PICCs (59.2%) were favored clinically, as was basilic vein placement (71.84%). Mean catheter dwell was 47.01 ± 25.82 days. Three (3, 2.9%) central line-associated bloodstream infections (CLABSI) were reported. Four patients (4.6%) reported symptomatic catheter-related thrombosis (CRT), confirmed with ultrasound. Three patients (3.4%) had ultrasound-confirmed fibroblastic sleeve (FS). Eight patients (9.2%) who entered the study with pre-existing superficial thrombosis, had complete resolution at the time of catheter removal. The incidence of CLABSI was 0.82/1000 days. The combined CRT and FS rate was 6.9%.

CONCLUSION

Based upon the observational findings of this study, chlorhexidine-coated PICC technology may be considered for use in patient populations who are at moderate to high-risk for catheter-related complications in both inpatient and outpatient settings.

Therapeutic applications of nanobiotechnology

Nanobiotechnology, as a novel and more specialized branch of science, has provided a number of nanostructures such as nanoparticles, by utilizing the methods, techniques, and protocols of other branches of science. Due to the unique features and physiobiological characteristics, these nanostructures or nanocarriers have provided vast methods and therapeutic techniques, against microbial infections and cancers and for tissue regeneration, tissue engineering, and immunotherapies, and for gene therapies, through drug delivery systems. However, reduced carrying capacity, abrupt and non-targeted delivery, and solubility of therapeutic agents, can affect the therapeutic applications of these biotechnological products. In this article, we explored and discussed the prominent nanobiotechnological methods and products such as nanocarriers, highlighted the features and challenges associated with these products, and attempted to conclude if available nanostructures offer any scope of improvement or enhancement. We aimed to identify and emphasize the nanobiotechnological methods and products, with greater prospect and capacity for therapeutic improvements and enhancements. We found that novel nanocarriers and nanostructures, such as nanocomposites, micelles, hydrogels, microneedles, and artificial cells, can address the associated challenges and inherited drawbacks, with help of conjugations, sustained and stimuli-responsive release, ligand binding, and targeted delivery. We recommend that nanobiotechnology, despite having few challenges and drawbacks, offers immense opportunities that can be harnessed in delivering quality therapeutics with precision and prediction. We also recommend that, by exploring the branched domains more rigorously, bottlenecks and obstacles can also be addressed and resolved in return.

Silver Nanoparticles Phytofabricated through Azadirachta indica: Anticancer, Apoptotic, and Wound-Healing Properties

Silver nanoparticles (AgNPs) have unlocked numerous novel disciplines in nanobiotechnological protocols due to their larger surface area-to-volume ratios, which are attributed to the marked reactivity of nanosilver, and due to their extremely small size, which enables AgNPs to enter cells, interact with organelles, and yield distinct biological effects. AgNPs are capable of bypassing immune cells, staying in the system for longer periods and with a higher distribution, reaching target tissues at higher concentrations, avoiding diffusion to adjacent tissues, releasing therapeutic agents or drugs for specific stimuli to achieve a longer duration at a specific rate, and yielding desired effects. The phytofabrication of AgNPs is a cost-effective, one-step, environmentally friendly, and easy method that harnesses sustainable resources and naturally available components of plant extracts (PEs). In addition, it processes various catalytic activities for the degradation of various organic pollutants. For the phytofabrication of AgNPs, plant products can be used in a multifunctional manner as a reducing agent, a stabilizing agent, and a functionalizing agent. In addition, they can be used to curtail the requirements for any additional stabilizing agents and to help the reaction stages subside. Azadirachta indica, a very common and prominent medicinal plant grown throughout the Indian subcontinent, possesses free radical scavenging and other pharmaceutical properties via the regulation of proinflammatory enzymes, such as COX and TOX. It also demonstrates anticancer activities through cell-signaling pathways, modulating tumor-suppressing genes such as p53 and pTEN, transcriptional factors, angiogenesis, and apoptosis via bcl2 and bax. In addition, it possesses antibacterial activities. Phytofabricated AgNPs have been applied in the areas of drug delivery, bioimaging, biosensing, cancer treatment, cosmetics, and cell biology. Such pharmaceutical and biological activities of phytofabricated AgNPs are attributed to more than 300 phytochemicals found in Azadirachta indica, and are especially abundant in flavonoids, polyphenols, diterpenoids, triterpenoids, limonoids, tannins, coumarin, nimbolide, azadirachtin, azadirone, azadiradione, and gedunin. Parts of Azadirachta indica, including the leaves in various forms, have been used for wound healing or as a repellent. This study was aimed at examining previously biosynthesized (from Azadirachta indica) AgNPs for anticancer, wound-healing, and antimicrobial actions (through MTT reduction assay, scratch assay, and microbroth dilution methods, respectively). Additionally, apoptosis in cancer cells and the antibiofilm capabilities of AgNPs were examined through caspase-3 expression, dentine block, and crystal violet methods. We found that biogenic silver nanoparticles are capable of inducing cytotoxicity in HCT-116 colon carcinoma cells (IC50 of 744.23 µg/mL, R2: 0.94), but are ineffective against MCF-7 breast cancer cells (IC50 >> 1000 µg/mL, R2: 0.86). AgNPs (IC50 value) induced a significant increase in caspase-3 expression (a 1.5-fold increase) in HCT-116, as compared with control cells. FITC-MFI was 1936 in HCT-116-treated cells, as compared to being 4551 in cisplatin and 1297 in untreated cells. AgNPs (6.26 µg/mL and 62.5 µg/mL) induced the cellular migration (40.2% and 33.23%, respectively) of V79 Chinese hamster lung fibroblasts; however, the improvement in wound healing was not significant as it was for the controls. AgNPs (MIC of 10 µg/mL) were very effective against MDR Enterococcus faecalis in the planktonic mode as well as in the biofilm mode. AgNPs (10 µg/mL and 320 µg/mL) reduced the E. faecalis biofilm by >50% and >80%, respectively. Natural products, such as Syzygium aromaticum (clove) oil (MIC of 312.5 µg/mL) and eugenol (MIC of 625 µg/mL), showed significant antimicrobial effects against A. indica. Our findings indicate that A. indica-functionalized AgNPs are effective against cancer cells and can induce apoptosis in HCT-116 colon carcinoma cells; however, the anticancer properties of AgNPs can also be upgraded through active targeting (functionalized with enzymes, antibiotics, photosensitizers, or antibodies) in immunotherapy, photothermal therapy, and photodynamic therapy. Our findings also suggest that functionalized AgNPs could be pivotal in the development of a novel, non-cytotoxic, biocompatible therapeutic agent for infected chronic wounds, ulcers, and skin lesions involving MDR pathogens via their incorporation into scaffolds, composites, patches, microgels, or formulations for microneedles, dressings, bandages, gels, or other drug-delivery systems.

Synthesis and Biological Characterization of Phyto-Fabricated Silver Nanoparticles from Azadirachta indica

Nanoparticles (NPs) have garnered a lot of interest in sectors like medicine, cosmetics, food, and pharmaceuticals for antibacterial catalytic properties, reduced toxicity, and easy production. Biological synthesis of silver nanoparticle (AgNPs) is considered as green, eco-friendly, and cost-effective approach; therefore, Azadirachta indica extracts were utilized for a dual role of fabrication and functionalization of AgNPs. Optical and physical characterizations were achieved for confirming the biosynthesized AgNPs. SEM images detected quasi-spherical AgNPs of 44.04 to 66.50 nm. Some of potent phytochemicals like flavonoids and proteins from Azadirachta indica formed a strong coating or capping on the AgNPs without affecting their secondary structure by interacting with Ag+ and NPs for the formation of AgNPs. AgNPs exhibited strong antibacterial activity (MIC 10 μg/ml) against multidrug-resistant bacteria Enterococcus faecalis; at different concentrations, no IC50 values were recorded for AgNPs as well as Azadirachta indica signifying low cytotoxicity in the exposed concentration range. The DNA degradation activity of AgNPs through the TUNEL assay revealed no significant increase in the overall FITC mean fluorescence intensity as well as a DNA fragmentation index with 5.45% DNA damage (10 μg/ml AgNPs). Drug uptake of AgNPs was also investigated through a permeability assay via Caco-2 cell lines at test concentrations where apparent permeability was detected as moderate.

Systems of conductive skin for power transfer in clinical applications

The primary aim of this article is to review the clinical challenges related to the supply of power in implanted left ventricular assist devices (LVADs) by means of transcutaneous drivelines. In effect of that, we present the preventive measures and post-operative protocols that are regularly employed to address the leading problem of driveline infections. Due to the lack of reliable wireless solutions for power transfer in LVADs, the development of new driveline configurations remains at the forefront of different strategies that aim to power LVADs in a less destructive manner. To this end, skin damage and breach formation around transcutaneous LVAD drivelines represent key challenges before improving the current standard of care. For this reason, we assess recent strategies on the surface functionalization of LVAD drivelines, which aim to limit the incidence of driveline infection by directing the responses of the skin tissue. Moreover, we propose a class of power transfer systems that could leverage the ability of skin tissue to effectively heal short diameter wounds. In this direction, we employed a novel method to generate thin conductive wires of controllable surface topography with the potential to minimize skin disruption and eliminate the problem of driveline infections. Our initial results suggest the viability of the small diameter wires for the investigation of new power transfer systems for LVADs. Overall, this review uniquely compiles a diverse number of topics with the aim to instigate new research ventures on the design of power transfer systems for IMDs, and specifically LVADs.

A minimally invasive catheterization of the external jugular vein in suckling piglets using ultrasound guidance

There is a growing interest for minimally invasive surgical procedures to improve experimental animal welfare. Minimally invasive catheterization procedures in pigs have been already developed using Seldinger technique but reproducibility is low, especially in young pigs. A novel method for a minimally invasive catheterization of external jugular vein was evaluated in suckling piglets of 21 days of age. Growth performance and haptoglobin concentration in plasma were measured throughout a four-week study in a group of seven catheterized piglets and a group of seven non-catheterized piglets. Catheterization was performed using Seldinger technique under continuous ultrasound monitoring for vein detection and needle insertion. The surgical procedure was quick and showed a great reproducibility. All catheters remained functional during the first week after catheterization. Catheterization in piglets did not significantly affect body weight (BW) and feed intake during four weeks after the surgical intervention compared to non-catheterized piglets (P > 0.10). Haptoglobin concentration in plasma was greater in catheterized piglets compared with non-catheterized piglets, with a significant increase over two weeks after catheter insertion (P < 0.05), suggesting the development of a chronic inflammation in catheterized piglets. This method can be easily performed in piglets with minimal effect on growth and feeding behaviour. Transposition to heavier pigs should be considered.

Promising Therapeutic Strategies Against Microbial Biofilm Challenges

Biofilms are communities of microorganisms that are attached to a biological or abiotic surface and are surrounded by a self-produced extracellular matrix. Cells within a biofilm have intrinsic characteristics that are different from those of planktonic cells. Biofilm resistance to antimicrobial agents has drawn increasing attention. It is well-known that medical device- and tissue-associated biofilms may be the leading cause for the failure of antibiotic treatments and can cause many chronic infections. The eradication of biofilms is very challenging. Many researchers are working to address biofilm-related infections, and some novel strategies have been developed and identified as being effective and promising. Nevertheless, more preclinical studies and well-designed multicenter clinical trials are critically needed to evaluate the prospects of these strategies. Here, we review information about the mechanisms underlying the drug resistance of biofilms and discuss recent progress in alternative therapies and promising strategies against microbial biofilms. We also summarize the strengths and weaknesses of these strategies in detail.

Understanding dental plaque; biofilm dynamics

A biofilm is a well organized community of cooperating microorganisms. Biofilms predictably form in nature, in artificial environments, and on medically implanted prostheses and indwelling venous catheters. They also form on tooth surfaces in the form of dental plaque. The intent of this article is to aid in the understanding of dental plaque by exploring biofilm structure, nature and dynamics. Understanding plaque facilitates its treatment and control.

Effectiveness of antimicrobial-coated central venous catheters for preventing catheter-related blood-stream infections with the implementation of bundles: a systematic review and network meta-analysis

Background

Catheter-related blood-stream infections (CRBSIs) are the most common complication when using central venous catheters (CVCs). Whether coating CVCs under bundles could further reduce the incidence of CRBSIs is unclear. We aimed to assess the effectiveness of implementing the use of bundles with antimicrobial-coated CVCs for preventing catheter-related blood-stream infections.

Methods

In this systematic review and network meta-analyses, we searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library in addition to the EMBASE, MEDLINE, CINAHL, and Web of Science databases for studies published before July 2017. The primary outcome was the rate of CRBSIs per 1000 catheter-days, and the secondary outcome was the incidence of catheter colonization.

Results

Twenty-three studies revealed significant differences in the rate of CRBSIs per 1000 catheter-days between antimicrobial-impregnated and standard CVCs (RR 0.70, 95% CI 0.53–0.91, p = 0.008). Thirty-three trials were included containing 10,464 patients who received one of four types of CVCs. Compared with a standard catheter, chlorhexidine/silver sulfadiazine- and antibiotic-coated catheters were associated with lower numbers of CRBSIs per 1000 catheter-days (ORs and 95% CrIs: 0.64 (0.40–0.955) and 0.53 (0.25–0.95), respectively) and a lower incidence of catheter colonization (ORs and 95% CrIs: 0.44 (0.34–0.56) and 0.30 (0.20–0.46), respectively).

Conclusions

Outcomes are superior for catheters impregnated with chlorhexidine/silver sulfadiazine or other antibiotics than for standard catheters in preventing CRBSIs and catheter colonization under bundles. Compared with silver ion-impregnated CVCs, chlorhexidine/silver sulfadiazine antiseptic catheters resulted in fewer cases of microbial colonization of the catheter but did not reduce CRBSIs.

Electronic supplementary material

The online version of this article (10.1186/s13613-018-0416-4) contains supplementary material, which is available to authorized users.

Chlorhexidine-coated peripherally inserted central catheters reduce fibroblastic sleeve formation in an in vivo ovine model

Purpose:

This study compared an antimicrobial and anti-thrombogenic peripherally inserted central catheter treated with a chlorhexidine-based technology, a peripherally inserted central catheter with bulk distributed fluoro-oligomers, and a poly 2-methoxyethyl acrylate–based peripherally inserted central catheter to an untreated peripherally inserted central catheter (control) in an ovine model at 14 and 30 days post-implant.

Methods:

One of four types of peripherally inserted central catheters was surgically implanted into the left jugular vein of each of 18 sheep for 14 or 30 days. Blood analysis consisted of complete blood counts, serum chemistries, and coagulation (fibrinogen, prothrombin time, and partial thromboplastin time) profiles. Sheep were sacrificed to examine the vein and thorax. Histological analysis was performed on serial catheter sections using standard microscopy on hematoxylin and eosin–stained tissues.

Results:

All catheters developed fibroblastic sleeves at both 14 and 30 days. The chlorhexidine-peripherally inserted central catheter showed a 64% lower mean fibroblastic sleeve weight and a 66% shorter mean fibroblastic sleeve length compared to the untreated control at 14 days. By 30 days, compared to untreated control, the chlorhexidine-peripherally inserted central catheter showed 81% lower mean fibroblastic sleeve weight with 75% shorter mean fibroblastic sleeve length, the fluoro-oligomer-peripherally inserted central catheter showed 54% lower mean sheath weight with 40% shorter mean fibroblastic sleeve length, and the poly 2-methoxyethyl acrylate-peripherally inserted central catheter had 41% lower mean fibroblastic sleeve weight with 57% lower fibroblastic sleeve length.

Conclusion:

Among the three anti-thrombogenic peripherally inserted central catheter technologies, the chlorhexidine-peripherally inserted central catheter had the smallest fibroblastic sleeves, followed by the fluoro-oligomer-peripherally inserted central catheter, poly 2-methoxyethyl acrylate-peripherally inserted central catheter, and control peripherally inserted central catheter.

Intravascular Catheters and Biofilm Control

Intravascular catheters are the most common cause of nosocomially acquired bloodstream infections. Bacteria found adhering to the intraluminal surfaces of catheters are the principal source and cause of these infections. Adherent bacteria overtime are known to form multicellular communities which become encased within a three dimensional matrix of extracellular polymeric material known as biofilms, which are thought to be responsible for persistent infections. Consequently, a number of technologies have been developed to help prevent and control biofilms in intravascular catheters. One such approach involves impregnating catheter material with antimicrobial agents. Unfortunately these methods are not universally effective in preventing catheter-related biofilm infections. Technologies that utilise antimicrobials, as catheter locks have been shown to have more potential for preventing biofilm formation and reducing the incidences of catheter related bloodstream infections (CRBSI). This article discusses the significance of biofilms in intravascular catheters and determines whether the treatments available today are proving to be effective for controlling biofilms and draws attention to future avenues which are being investigated to control biofilms and therefore CRBSI.

Complex poly(lactic acid)-based biomaterial for urinary catheters: I. Influence of AgNP on properties

The present study focused on the development of biocompatible antimicrobial/antioxidant biodegradable bionanocomposite renewable resources based on poly(lactic acid) (PLA) plasticised with epoxidised soybean oil. To the main PLA matrix hydrolysed collagen (HC) (to enhance biocompatibility), vitamin E (as antioxidant agent) and silver (Ag) nanoparticles (NPs) (for imparting antimicrobial properties for medical applications and also for active packaging) were incorporated. The blends were produced by using the classical technological flow of melt processing. The presence of the additives in the PLA matrix improved the processability and flexibility and slightly decreased the thermal properties. The specific interactions of silver NPs with the other components of nanocomposites, mainly with HC protein and vitamin E (by ionic and other types of secondary bonds), led to a better HC and vitamin E dispersion in the samples with a higher silver content (1·5%), which further caused the enhancement of the mechanical properties for high silver NP concentration. Therefore, the silver NPs were successfully embedded into the polymer matrix. The aim of this research was to improve the flexibility, biocompatibility and functionality of PLA and to obtain bionanocomposites destined for medical applications such as catheters. This first part of research deals with mechanical and thermal characterisation correlated with morphological features.

Co-release of dicloxacillin and thioridazine from catheter material containing an interpenetrating polymer network for inhibiting device-associated Staphylococcus aureus infection

Approximately half of all nosocomial bloodstream infections are caused by bacterial colonization of vascular catheters. Attempts have been made to improve devices using anti-adhesive or antimicrobial coatings; however, it is often difficult to bind coatings stably to catheter materials, and the low amounts of drug in thin-film coatings limit effective long-term release. Interpenetrating polymer networks (IPNs) are polymer hybrid materials with unique drug release properties. While IPNs have been extensively investigated for use in tablet- or capsule-based drug delivery systems, the potential for use of IPNs in drug release medical devices remains largely unexplored. Here, we investigated the use of silicone-hydrogel IPNs as a catheter material to provide slow anti-bacterial drug-release functionality. IPN catheters were produced by the sequential method, using supercritical CO₂ as a solvent to polymerize and crosslink poly(2-hydroxyethyl methacrylate) (PHEMA) in silicone elastomer. The design was tested against Staphylococcus aureus colonization after loading with dicloxacillin (DCX) alone or in combination with thioridazine (TDZ), the latter of which is known to synergistically potentiate the antibacterial effect of DCX against both methicillin-sensitive and methicillin-resistant S. aureus. The hydrophilic PHEMA component allowed for drug loading in the catheters by passive diffusion and provided controlled release properties. The drug-loaded IPN material inhibited bacterial growth on agar plates for up to two weeks and in blood cultures for up to five days, and it withstood 24h of seeding with resilient biofilm aggregates. The combined loading of DCX+TDZ enhanced the antibacterial efficiency in static in vitro experiments, although release analyses revealed that this effect was due to an enhanced loading capacity of DCX when co-loaded with TDZ. Lastly, the IPN catheters were tested in a novel porcine model of central venous catheter-related infection, in which drug-loaded IPN catheters were found to significantly decrease the frequency of infection.

Application of Targeted Molecular and Material Property Optimization to Bacterial Attachment-Resistant (Meth)acrylate Polymers

Developing medical devices that resist bacterial attachment and subsequent biofilm formation is highly desirable. In this paper, we report the optimization of the molecular structure and thus material properties of a range of (meth)acrylate copolymers which contain monomers reported to deliver bacterial resistance to surfaces. This optimization allows such monomers to be employed within novel coatings to reduce bacterial attachment to silicone urinary catheters. We show that the flexibility of copolymers can be tuned to match that of the silicone catheter substrate, by copolymerizing these polymers with a lower Tg monomer such that it passes the flexing fatigue tests as coatings upon catheters, that the homopolymers failed. Furthermore, the Tg values of the copolymers are shown to be readily estimated by the Fox equation. The bacterial resistance performance of these copolymers were typically found to be better than the neat silicone or a commercial silver containing hydrogel surface, when the monomer feed contained only 25 v% of the "hit" monomer. The method of initiation (either photo or thermal) was shown not to affect the bacterial resistance of the copolymers. Optimized synthesis conditions to ensure that the correct copolymer composition and to prevent the onset of gelation are detailed.

Inhibition of Staphylococcus Epidermidis Colonization with Fusidic Acid-Impregnated Catheters

The aim of this study was the preparation and characterization of fusidic acid-impregnated peripheral catheters. In the first part of the study, in vitro drug release studies were performed, and the effect of fusidic acid impregnation on adherence of slime positive Staphylococcus epidermidis to catheters was evaluated as in vitro studies. Fusidic acid-impregnated and naïve catheters were incubated with 108 colony forming unit/mL (cfu/mL) slime positive S. epidermidis during the in vitro experiment. After incubation for 2, 4, 6, 8, 12, 24, 48, and 72 h, the number of colonies were determined in an aliquot and adhered to the catheter. During the in vivo experiment, contaminated naïve and fusidic acid-impregnated catheters ( n = 10 rats in both groups) were implanted subcutaneously in the back of the rats. Rats were killed at the end of the seventh day and catheters were removed. Microbiologic assessments from the explanted catheter segments were performed. Fusidic acid impregnation decreased the number of adherent bacteria to the catheters and the number of free bacteria within the liquid medium significantly. There were 3 positive catheter cultures out of 10 in rats implanted with fusidic acid-impregnated catheters, whereas all explanted catheters from naïve group yielded bacterial growth. The mean cfu counts were significantly less in the fusidic acid-impregnated catheter group. In vitro release studies and antibacterial activity studies correlated well. Additionally, morphological evaluations by scanning electron microscopy showed that fewer bacteria were evident on the fusidic acid-impregnated catheters compared with naïve catheters. As a conclusion, catheter impregnation with fusidic acid is effective in preventing colonization in these in vitro and in vivo sets of experiments, with slime-producing S. epidermidis.

Biofilm formation in total hip arthroplasty: prevention and treatment

This review assesses the current knowledge on treatments, pathogenesis and the prevention of infections associated with orthopaedic implants, with a focus on total hip arthroplasty.

Guideline for Prevention of Intravascular-Device–Related Infections

The “Guideline for Prevention of Intravascular Device-Related Infections” is designed to reduce the incidence of intravascular device-related infections by providing an over view of the evidence for recommendations considered prudent by consensus of Hospital Infection Control Practices Advisor y Committee (HICPAC) members. This two-part document updates and replaces the previously published Centers for Disease Control's (CDC) Guideline for Intravascular Infections (Am J Infect Control1983;11:183-199). Part I, “Intravascular Device-Related Infections: An Over view” discusses many of the issues and controversies in intravascular-device use and maintenance. These issues include definitions and diagnosis of catheter-related infection, appropriate barrier precautions during catheter insertion, inter vals for replacement of catheters, intravenous (IV) fluids and administration sets, catheter-site care, the role of specialized IV personnel, and the use of prophylactic antimi-crobials, flush solutions, and anticoagulants. Part II, “Recommendations for Prevention of Intravascular Device-Related Infections” provides consensus recommendations of the HICPAC for the prevention and control of intravascular device-related infections. A working draft of this document also was reviewed by experts in hospital infection control, internal medicine, pediatrics, and intravenous therapy. However, all recommendations contained in the guideline may not reflect the opinion of all reviewers.

Bacteria repelling poly(methylmethacrylate-co-dimethylacrylamide) coatings for biomedical devices†Electronic supplementary information (ESI) available: Polymer microarray screening, including analysis of bacterial adhesion by fluorescence microscopy and SEM, and chemical composition of bacteria repelling polymers identified in the screen; polymer synthesis and characterisation; preparation of catheter pieces and solvent studies, and details for confocal imaging/analysis. See DOI: 10.1039/c4tb01129eClick here for additional data file

A polymer microarray screen identified poly(methylmethacrylate-co-dimethylacrylamide) as a bacteria repelling surface, which substantially reduced binding of bacteria on coated catheters.

Nosocomial infections due to bacteria have serious implications on the health and recovery of patients in a variety of medical scenarios. Since bacterial contamination on medical devices contributes to the majority of nosocomical infections, there is a need for redesigning the surfaces of medical devices, such as catheters and tracheal tubes, to resist the binding of bacteria. In this work, polyurethanes and polyacrylates/acrylamides, which resist binding by the major bacterial pathogens underpinning implant-associated infections, were identified using high-throughput polymer microarrays. Subsequently, two ‘hit’ polymers, PA13 (poly(methylmethacrylate-co-dimethylacrylamide)) and PA515 (poly(methoxyethylmethacrylate-co-diethylaminoethylacrylate-co-methylmethacrylate)), were used to coat catheters and substantially shown to decrease binding of a variety of bacteria (including isolates from infected endotracheal tubes and heart valves from intensive care unit patients). Catheters coated with polymer PA13 showed up to 96% reduction in bacteria binding in comparison to uncoated catheters.

Ventricular assist device driveline infection: treatment with platelet-rich plasma

We report a case of autologous platelet-rich plasma (PRP) application over the driveline site of a left ventricular assist device (LVAD) to treat an infection. The patient, a 47-year-old man with end-stage dilated cardiomyopathy, underwent Jarvik 2000 implantation through a median sternotomy. A pedestal with power supply and LVAD control was implanted into the mastoid bone. Retroauricular wound dehiscence occurred, and PRP was applied over the wound. Normal healing of the driveline exit site was observed. PRP can be used at a driveline exit site to either prevent or treat wound infection.

Discovery of novel materials with broad resistance to bacterial attachment using combinatorial polymer microarrays

A new class of bacteria-attachment-resistant materials is discovered using a multi-generation polymer microarray methodology that reduces bacterial attachment by up to 99.3% compared with a leading commercially available silver hydrogel anti-bacterial material. The coverage of three bacterial species, Pseudomonas aeruginosa, Staphylococcus aureus, and uropathogenic Escherichia coli is assessed.

Combinatorial discovery of polymers resistant to bacterial attachment

Bacterial attachment and subsequent biofilm formation pose key challenges to the optimal performance of medical devices. In this study, we determined the attachment of selected bacterial species to hundreds of polymeric materials in a high-throughput microarray format. Using this method, we identified a group of structurally related materials comprising ester and cyclic hydrocarbon moieties that substantially reduced the attachment of pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli). Coating silicone with these 'hit' materials achieved up to a 30-fold (96.7%) reduction in the surface area covered by bacteria compared with a commercial silver hydrogel coating in vitro, and the same material coatings were effective at reducing bacterial attachment in vivo in a mouse implant infection model. These polymers represent a class of materials that reduce the attachment of bacteria that could not have been predicted to have this property from the current understanding of bacteria-surface interactions.

Silver polymeric nanocomposites as advanced antimicrobial agents: classification, synthetic paths, applications, and perspectives

Utilization of metallic nanoparticles in various biotechnological and medical applications represents one of the most extensively investigated areas of the current materials science. These advanced applications require the appropriate chemical functionalization of the nanoparticles with organic molecules or their incorporation in suitable polymer matrices. The intensified interest in polymer nanocomposites with silver nanoparticles is due to the high antimicrobial effect of nanosilver as well as the unique characteristics of polymers which include their excellent structural uniformity, multivalency, high degree of branching, miscellaneous morphologies and architectures, and highly variable chemical composition. In this review, we explore several aspects of antimicrobial polymer silver nanocomposites, giving special focus to the critical analysis of the reported synthetic routes including their advantages, drawbacks, possible improvements, and real applicability in antibacterial and antifungal therapy. A special attention is given to "green" synthetic routes exploiting the biopolymeric matrix and to the methods allowing preparing magnetically controllable antimicrobial polymers for targeting to an active place. The controversial mechanism of the action of silver against bacteria, fungi and yeasts as well as perspectives and new applications of silver polymeric nanocomposites is also briefly discussed.

Molding a silver nanoparticle template on polydimethylsiloxane to efficiently capture mammalian cells

Herein, a functional template made up of in situ synthesized silver nanoparticles (AgNPs) is prepared on polydimethylsiloxane (PDMS) for the spatial control of cell capture, where the residual Si-H groups in the PDMS matrix are used as reductants to reduce AgNO(3) for forming AgNPs. In virtue of microfluidic system, a one-dimensional array pattern of AgNPs is obtained easily. Further combining with plasma treatment, a two-dimensional array pattern of AgNPs could be achieved. The obtained PDMS-AgNPs composite is characterized in detail. The PDMS-AgNPs composite shows good antibacterial property in E. coli adhesion tests. The patterns possess hifi and high resolution (ca. 8 microm). Cell patterns with high efficiency and spatial selectivity are further formed with the aid of H-Arg-Gly-Asp-Cys-OH (RGDC) tetrapeptide which is grafted on the AgNPs template. Cells immobilized on the template show a good ability for adhesion, spreading, migration, and growth.

Late-Onset Driveline Infections: The Achilles’ Heel of Prolonged Left Ventricular Assist Device Support

BACKGROUND

A successful left ventricular assist device (LVAD) long-term support in an outpatient setting demands that device-related complications are reduced to a minimum. We hypothesized that late onset driveline infections have serious implications on the anticipated application of LVAD as permanent therapy.

METHODS

Between 1996 and 2005, 73 patients were implanted with the Novacor (World Heart Corp, Ottawa, Ontario, Canada; n = 35) or the HeartMate (Thoratec Corp, Pleasanton, CA; n = 38) as either bridge to transplantation (n = 44) or destination therapy (n = 29). Our analysis focused on patients with late-onset infection (> or = 30 days) of the driveline exit site with prior clinical healing of all incisions.

RESULTS

Late driveline infections developed in 17 patients (23%) at a median of 158 days (intraquartile range [IQR]: 68 to 213 days) after implantation. The median duration of support in this subgroup was 400 days (IQR, 283 to 849 days). Despite an aggressive treatment algorithm, repeat surgical revision was needed in 12 patients, up to six times in 2 individuals. In 6 patients, the infection progressed to pump pocket infections that led to urgent heart transplantation (n = 4) or explantation (n = 2). The individual risk that a driveline infection would develop dramatically increased with the duration of support, reaching 94% at 1 year. Multivariate analysis identified duration of support (p < 0.001) and documented trauma at the driveline exit site (p < 0.001) as independent predictors of infection. Number and duration of readmissions to the hospital significantly increased (p < 0.001), and long-term follow-up for survival (4.4 +/- 2.2 years, 100% complete) showed a trend towards impaired outcome after driveline infection (5-year survival: 41% versus 70%, p = 0.10).

CONCLUSIONS

Long-term LVAD support in the current series was jeopardized by late-onset driveline infections, which occurred in all patients with support duration longer than 1 year. Once driveline infections developed, they were difficult to control and significantly increased morbidity.

In vitro anti-bacterial and biological properties of magnetron co-sputtered silver-containing hydroxyapatite coating

Bacterial infection after implant placement is a significant rising complication. In order to reduce the incidence of implant-associated infections, several biomaterial surface treatments have been proposed. In this study, the effect of in vitro antibacterial activity and in vitro cytotoxicity of co-sputtered silver (Ag)-containing hydroxyapatite (HA) coating was evaluated. Deposition was achieved by a concurrent supply of 10 W to the Ag target and 300 W to the HA target. Heat treatment at 400 degrees C for 4 h was performed after 3 h deposition. X-ray diffraction, contact angles measurements, and surface roughness were used to characterize the coating surfaces. The RP12 strain of Staphylococcus epidermidis (ATCC 35984) and the Cowan I strain of Staphylococcus aureus were used to evaluate the antibacterial activity of the Ag-HA coatings, whereas human embryonic palatal mesenchyme cells, an osteoblast precursor cell line, were used to evaluate the in vitro cytotoxicity of the coatings. X-ray diffraction analysis performed in this study indicated peaks corresponding to Ag and HA on the co-sputtered Ag-HA surfaces. The contact angles for HA and Ag-HA surfaces were observed to be significantly lower when compared to Ti surfaces, whereas no significant difference in surface roughness was observed for all groups. In vitro bacterial adhesion study indicated a significantly reduced number of S. epidermidis and S. aureus on Ag-HA surface when compared to titanium (Ti) and HA surfaces. In addition, no significant difference in the in vitro cytotoxicty was observed between HA and Ag-HA surfaces. Overall, it was concluded that the creation of a multifunctional surface can be achieved by co-sputtering the osteoconductive HA with antibacterial Ag.

Efficacy of antiseptic-impregnated catheters on catheter colonization and catheter-related bloodstream infections in patients in an intensive care unit

This study was conducted to evaluate the impact of central venous catheters impregnated with chlorhexidine and silver sulphadiazine on the incidence of colonization and catheter-related bloodstream infection in critically ill patients. One hundred and thirty-three patients requiring central venous catheterization were chosen at random to receive either an antiseptic-impregnated triple-lumen catheter (N=64) or a standard triple-lumen catheter (N=69). The mean (SD) durations of catheterization for the antiseptic and standard catheters were 11.7 (5.8) days (median 10; range 3-29) and 8.9 (4.6) days (median 8.0; range 3-20), respectively (P=0.006). Fourteen (21.9%) of the antiseptic catheters and 14 (20.3%) of the standard catheters had been colonized at the time of removal (P=0.834). Four cases (6.3%) of catheter-related bloodstream infection were associated with antiseptic catheters and one case (1.4%) was associated with a standard catheter (P=0.195). The catheter colonization rates were 18.7/1000 catheter-days for the antiseptic catheter group and 22.6/1000 catheter-days for the standard catheter group (P=0.640). The catheter-related bloodstream infection rates were 5.3/1000 catheter-days for the antiseptic catheter group and 1.6/1000 catheter-days for the standard catheter group (P=0.452). In conclusion, our results indicate that the use of antiseptic-impregnated central venous catheters has no effect on the incidence of either catheter colonization or catheter-related bloodstream infection in critically ill patients.

Benefits of minocycline and rifampin-impregnated central venous catheters

OBJECTIVE

To determine the efficacy of minocycline and rifampin-impregnated catheters compared to non-impregnated catheters in critically ill patients.

DESIGN

Prospective, randomized, double-blind, controlled, multicenter trial.

SETTING

Intensive care units of seven acute-care teaching hospitals in Spain. PATIENTS. Intensive care unit patients requiring triple-lumen central venous catheter for more than 3 days.

INTERVENTIONS

At catheter insertion, 228 patients were randomized to minocycline and rifampin-impregnated catheters and 237 to non-impregnated catheters. Skin, catheter tip, subcutaneous segment, hub cultures, peripheral blood and infusate cultures were performed at catheter withdrawal. The rate of colonization, catheter-related bloodstream infection (CRBSI) and catheter-related clinical infectious complications (purulence at the insertion site or CRBSI) were assessed.

MEASUREMENTS AND MAIN RESULTS

In the intention-to-treat analysis (primary analysis), the episodes per 1000 catheter days of clinical infectious complications decreased from 8.6 to 5.7 (RR =0.67, 95% CI 0.31-1.44), CRBSI from 5.9 to 3.1 (RR =0.53, 95% CI 0.2-1.44) and tip colonization from 24 to 10.4 (RR =0.43, 95% CI 0.26-0.73). Antimicrobial-impregnated catheters were associated with a significant decrease of coagulase-negative staphylococci colonization (RR =0.24, 95% CI 0.13-0.45) and a significant increase of Candida spp. colonization (RR =5.84, 95% CI 1.31-26.1).

CONCLUSIONS

The use of antimicrobial-impregnated catheters was associated with a significantly lower rate of coagulase-negative staphylococci colonization and a significant increase in Candida spp. colonization, although a decrease in CRBSI, increase in 30-day survival or reduced length of stay was not observed.

Antiseptic impregnated endotracheal tubes for the prevention of bacterial colonization

The effect of endotracheal tubes (ETTs) impregnated with chlorhexidine (CHX) and silver carbonate (antiseptic ETTs) against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Pseudomonas aeruginosa, Acinetobacter baumannii, and Enterobacter aerogenes [organisms associated with ventilator-associated pneumonia (VAP)], was evaluated in a laboratory airway model. Antiseptic ETTs and control ETTs (unimpregnated) were inserted in culture tubes half-filled with agar media (airway model) previously contaminated at the surface with 10(8) cfu/mL of the selected test organism. After five days of incubation, bacterial colony counts on all ETT segments were determined. Swabs of proximal and distal ends of the agar tract in antiseptic and control models were subcultured. The initial and residual CHX levels, (five days post-implantation in the model) were determined. Cultures of antiseptic ETTs revealed colonization by the tested pathogens ranging from 1-100 cfu/tube, compared with approximately 10(6) cfu/tube for the control ETTs (P < 0.001). Subcultures from proximal and distal ends of the agar tract showed minimal or no growth in the antiseptic ETTs compared with the control ETTs (P < 0.001). The amount of CHX retained in the antiseptic ETTs after five days of implantation was an average of 45% of the initial level. Antiseptic ETTs prevented bacterial colonization in the airway model and also retained significant amounts of the antiseptic. These results indicate that the effectiveness of antiseptic-impregnated ETTs in preventing the growth of bacterial pathogens associated with VAP may vary with different organisms.

Clinical review: new technologies for prevention of intravascular catheter-related infections

Intravascular catheters have become essential devices for the management of critically and chronically ill patients. However, their use is often associated with serious infectious complications, mostly catheter-related bloodstream infection (CRBSI), resulting in significant morbidity, increased duration of hospitalization, and additional medical costs. The majority of CRBSIs are associated with central venous catheters (CVCs), and the relative risk for CRBSI is significantly greater with CVCs than with peripheral venous catheters. However, most CVC-related infections are preventable, and different measures have been implemented to reduce the risk for CRBSI, including maximal barrier precautions during catheter insertion, catheter site maintenance, and hub handling. The focus of the present review is on new technologies for preventing infections that are directed at CVCs. New preventive strategies that have been shown to be effective in reducing risk for CRBSI, including the use of catheters and dressings impregnated with antiseptics or antibiotics, the use of new hub models, and the use of antibiotic lock solutions, are briefly described.

Evaluation of the antimicrobial efficacy of urinary catheters impregnated with antiseptics in an in vitro urinary tract model

OBJECTIVES

To evaluate the long-term efficacy of urinary Foley catheters (latex and silicone) impregnated with (1) chlorhexidine and silver sulfadiazine (CXS) and (2) chlorhexidine, silver sulfadiazine, and triclosan (CXST) in inhibiting extra-luminal bacterial adherence and to compare their efficacy with that of silver hydrogel latex (SH) and nitrofurazone-treated silicone (NF) catheters.

DESIGN

The antimicrobial spectrum of these catheters was evaluated using a zone of inhibition assay. A novel in vitro urinary tract model was developed to study the potential in vivo efficacy of antimicrobial catheters in preventing extraluminal bacterial colonization. The "meatus" was inoculated daily with Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Enterococcus faecalis, Pseudomonas aerginosa, and Candida albicans. The "bladder" portion of the model was cultured daily to determine bacterial growth.

RESULTS

Both CXS and CXST catheters had a broader antimicrobial spectrum than SH and NF catheters. In the in vitro model, CXST latex and silicone catheters exhibited significantly better efficacy (3 to 25days) against uropathogens, compared with CXS (1 to 14 days) and control (0 to 5 days) catheters (P = .01). CXST latex catheters exhibited significantly longer protection against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa, compared with SH catheters (P = .01). CXST silicone catheters resisted colonization with Staphylococcus aureus and Staphylococcus epidermidis for a significantly longer period (23 to 24 days) than did NF catheters (9 to 11 days) (P = .01).

CONCLUSION

Catheters impregnated with synergistic combinations of chlorhexidine, silver sulfadiazine, and triclosan exhibited broad-spectrum, long-term resistance against microbial colonization on their outer surfaces.

Bacterial silver resistance: molecular biology and uses and misuses of silver compounds

Resistance to silver compounds as determined by bacterial plasmids and genes has been defined by molecular genetics. Silver resistance conferred by the Salmonella plasmid pMGH100 involves nine genes in three transcription units. A sensor/responder (SilRS) two-component transcriptional regulatory system governs synthesis of a periplasmic Ag(I)-binding protein (SilE) and two efflux pumps (a P-type ATPase (SilP) plus a three-protein chemiosmotic RND Ag(I)/H+ exchange system (SilCBA)). The same genes were identified on five of 19 additional IncH incompatibility class plasmids but thus far not on other plasmids. Of 70 random enteric isolates from a local hospital, isolates from catheters and other Ag-exposed sites, and total genomes of enteric bacteria, 10 have recognizable sil genes. The centrally located six genes are found and functional in the chromosome of Escherichia coli K-12, and also occur on the genome of E. coli O157:H7. The use of molecular epidemiological tools will establish the range and diversity of such resistance systems in clinical and non-clinical sources. Silver compounds are used widely as effective antimicrobial agents to combat pathogens (bacteria, viruses and eukaryotic microorganisms) in the clinic and for public health hygiene. Silver cations (Ag+) are microcidal at low concentrations and used to treat burns, wounds and ulcers. Ag is used to coat catheters to retard microbial biofilm development. Ag is used in hygiene products including face creams, "alternative medicine" health supplements, supermarket products for washing vegetables, and water filtration cartridges. Ag is generally without adverse effects for humans, and argyria (irreversible discoloration of the skin resulting from subepithelial silver deposits) is rare and mostly of cosmetic concern.

The effect of increasing copper content in phosphate-based glasses on biofilms of Streptococcus sanguis

This paper reports the effect of a series of phosphate-based glasses based on the Na(2)O-CaO-P(2)O(5) system doped with increasing amounts of copper and the effect of this increasing copper content on the viability of an in vitro biofilm of Streptococcus sanguis over an 8 day period in a constant depth film fermenter. The addition of copper to the glass caused the solubility to change, so the glasses were adjusted in order that their solubility in artificial saliva was nominally the same (0.3062 +/- 0.07 mg cm(-2) h(-1)). Initial experiments on glasses with 1.5% and 10% copper showed that after 6 h there was no statistical difference between the copper containing glasses and the non-copper containing glass and HA in terms of the viability of the biofilms. However, at 24 h there was an approximately 0.8-0.9 log reduction in viability of the biofilms grown on the 5% copper glass and an approximately 1.0-1.3 log reduction for the 10% copper containing glass. Further experiments on the glass with 10% copper and another glass with 15% copper were carried out in a time dependent study. For both glasses a clear decrease in viable counts at 24 h was found but for both glasses these returned to levels similar to those of controls. The initial decrease in viability during the first 24 h is likely to be due to the antibacterial effect of the copper and this could be correlated with copper content. The recovery after 24 h is probably due to the dead cells forming a barrier, making diffusion of the antibacterial ions, increasingly difficult. This study has shown that phosphate-based glasses could potentially be used to deliver antibacterial ions to help combat oral infections. Copper, which has been shown to have antibacterial properties, could be incorporated but some development of the glasses used in this investigation may be required. Further work is needed to determine the effectiveness of copper containing glasses on oral bacterial communities.

Antibiofilm approaches: prevention of catheter colonization

Bacteria frequently attach to medical devices such as intravascular catheters by forming sessile multicellular communities known as biofilms, which can be the source of persistent infections that are recalcitrant to systemic antibiotic therapy. As a result of this persistence, a number of technologies have been developed to prevent catheter-associated biofilm formation. Whereas the most straightforward approaches focus on impregnating catheter material with classical antimicrobial agents, these approaches are not universally effective, thereby underscoring the need for more potent and more sophisticated approaches to the prevention of catheter-related biofilm infections.

Physicochemical characterization of hexetidine-impregnated endotracheal tube poly(vinyl chloride) and resistance to adherence of respiratory bacterial pathogens

PURPOSE

Ventilator-associated pneumonia is a frequent cause of mortality in intensive care patients. This study describes the physicochemical properties of hexetidine-impregnated poly(vinyl chloride) (PVC) endotracheal tube (ET) biomaterials and their resistance to microbial adherence (Staphylococcus aureus and Pseudomonas aeruginosa).

METHODS

PVC emulsion was cured in the presence of hexetidine (0-20% w/w) and was characterized in terms of drug release, surface properties (i.e., microrugosity/contact angle), mechanical (tensile) properties, and resistance to microbial adherence.

RESULTS

Under sink conditions, hexetidine release from PVC was diffusion-controlled. Increasing the concentration of hexetidine from 1% to 10% (w/w) (but not from 10% to 20% w/w) increased the subsequent rate of drug release. In general, increasing the concentration of hexetidine decreased both the tensile properties and hydrophobicity, yet increased PVC microrugosity. Following hexetidine release (21 days), the surface properties were similar to those of native PVC. The resistance of hexetidine-containing PVC (1% or 5%) to microbial adherence (following defined periods of drug release) was greater than that of native PVC and was constant over the examined period of hexetidine release.

CONCLUSIONS

ET PVC containing 1% (w/w) hexetidine offered an appropriate balance between suitable physicochemical properties and resistance to microbial adherence. This may offer an approach with which to reduce the incidence of ventilator-associated pneumonia.

Silver. I: Its antibacterial properties and mechanism of action

Silver products have two key advantages: they are broad-spectrum antibiotics and are not yet associated with drug resistance. This article, the first in a two-part series, describes the main mechanism of action of this metallic element.

Evaluation of an antimicrobial-impregnated continuous ambulatory peritoneal dialysis catheter for infection control in rats

Infection is the most serious complication arising in long-term continuous ambulatory peritoneal dialysis (CAPD), specifically peritonitis and exit-site infection. The initial weeks after implantation is the crucial period during which bacterial colonization of the catheter results in maximal morbidity, with Staphylococcus aureus being the most virulent organism. We developed an antimicrobial-impregnated CAPD catheter by impregnating the cuff and tubing with chlorhexidine, silver sulfadiazine, and triclosan in a polymer matrix. The antimicrobial spectrum and duration were shown by measuring zones of inhibition to various bacteria and fungi over the course of 5 to 10 days. Activity also was assessed subsequent to soaking in trypticase soy broth containing 20% bovine serum over the course of 1, 3, and 7 days. Significant antimicrobial activity was shown against all organisms tested for, with particular efficacy against gram-positive bacteria. Catheters were implanted in rats followed by inoculation of the exit site with S aureus. Seven days postimplantation, 0% of the impregnated catheters were colonized intraperitoneally compared with 100% of the control catheters. Similarly, 12.5% of the impregnated catheters were colonized at the exit site, whereas 100% of the controls were colonized. Histologic analysis showed that this combination and concentration of antimicrobials did not retard healing or cause increased inflammation compared with control catheters after 3, 10, and 24 days postimplantation in noninoculated rats.

Efficacy of antiadhesive, antibiotic and antiseptic coatings in preventing catheter-related infections: review

In recent years, central venous catheters (CVCs) are increasingly used in clinical practice. However, complications such as local or systemic infections are frequent for both temporary and indwelling vascular catheters. Annually, in the United States of America there are more than 200,000 cases of nosocomial bloodstream infections (BSIs), of which 90% are related to the use of an intravascular device. These infections are associated with increased morbidity and mortality, prolonged hospitalization and growing medical costs. Technological treatments of polymer surfaces including coating the catheter with antimicrobial substances may be promising tools for prevention of catheter-associated infections. A large number of surface-treated central venous catheters are now commercially available. In this paper the features and the clinical efficacy of different antimicrobial coatings are reviewed.

Safety and efficacy of an improved antiseptic catheter impregnated intraluminally with chlorhexidine

The safety and efficacy of a second-generation improved antiseptic catheter impregnated with silver sulfadiazine and increased levels of chlorhexidine on its outer surface and chlorhexidine alone on its luminal surfaces was compared in vitro and in vivo to standard antiseptic catheters impregnated with these antimicrobials on their outer surfaces only. In rat and pig intravenous models, the improved antiseptic catheter was significantly more effective in resisting both outer surface and luminal colonization compared with the standard antiseptic or control catheters. There was no evidence of tissue toxicity in any group.

Durability of anti-infective effect of long-term silicone sheath catheters impregnated with antimicrobial agents

This study was performed to test the long-term antimicrobial efficacy of impregnated silicone catheters comprising an antimicrobial layer sandwiched between an external surface sheath and a luminal surface silicone sheath. The design of the catheter permits the introduction of various antimicrobials in addition to anticoagulants or antifibrins in the antimicrobial layer and allows their gradual release over a period of months after insertion. The in vitro data presented show that the catheter can provide antimicrobial activity for 90 days, after being replated for 15 7-day cycles of replating. When the catheters were immersed in human serum and incubated at 37 degrees C, they demonstrated significant antimicrobial activity after more than 325 days of incubation. The significant long-term in vitro antimicrobial activity observed may imply effective in vivo activity for almost 1 year after insertion and could serve as a cost-effective alternative to surgically implantable silicone catheters.

Self-sterilizing and self-cleaning of silicone catheters coated with TiO(2) photocatalyst thin films: a preclinical work

TiO(2) photocatalysts were successfully coated on silicone catheters or medical tubes by pretreatment of the silicone surface with a sulfuric acid solution (5 M) for 3 h. The TiO(2) film adhered to the silicone substrate strongly against tensile and bending stresses. On the TiO(2)-coated silicone-catheters under UV illumination, both the bleaching of methylene blue dye and the photocatalytic bactericidal effect on Escherichia coli (E. coli) cells were confirmed. Thus, this type of catheter can be sterilized and cleaned simply by irradiation with low-intensity UV light and can, therefore, be useful in the protection from catheter-related bacterial infections.

In vitro evaluation of the risk of developing bacterial resistance to antiseptics and antibiotics used in medical devices

The risk of development of resistance in Staphylococcus epidermidis to the antibiotics and antiseptics impregnated in central venous catheters was evaluated. The culture was passaged 10-20 times through subinhibitory concentrations of different antimicrobials, singly and in combination, and the MIC of each antimicrobial before and after passage was compared. There was a 10- to 16-fold increase in the MIC of the combination of minocycline and rifampicin, while no significant increase in the MIC of minocycline alone was seen. The MIC of rifampicin was 25,000-fold higher against strains passaged through rifampicin alone (as compared with that for the original strain), while the increase was only 80-fold when it was combined with minocycline for passage. There was no substantial change in susceptibility to the antiseptic chlorhexidine when used alone or in combination with either silver sulphadiazine or triclosan (the MIC of triclosan alone increased eight-fold). In time-kill studies, synergy was observed between chlorhexidine and both triclosan and silver sulphadiazine. Zone of inhibition tests of catheters impregnated with minocycline and rifampicin showed that their activity against rifampicin-resistant strains was lower than that against the susceptible strain. On the other hand, the activity of the antiseptic (chlorhexidine and silver sulphadiazine) catheters against the rifampicin-resistant and -susceptible strains was similar. Although this study indicates that antibiotic catheters may be at a higher risk of being colonized by antibiotic-resistant bacteria, the implications of these results in clinical settings need to be determined.

Self-sterilizing and self-cleaning of silicone catheters coated with TiO(2) photocatalyst thin films: a preclinical work

TiO(2) photocatalysts were successfully coated on silicone catheters or medical tubes by pretreatment of the silicone surface with a sulfuric acid solution (5 M) for 3 h. The TiO(2) film adhered to the silicone substrate strongly against tensile and bending stresses. On the TiO(2)-coated silicone-catheters under UV illumination, both the bleaching of methylene blue dye and the photocatalytic bactericidal effect on Escherichia coli (E. coli) cells were confirmed. Thus, this type of catheter can be sterilized and cleaned simply by irradiation with low-intensity UV light and can, therefore, be useful in the protection from catheter-related bacterial infections.

Infectious complications associated with ventricular assist systems

Infectious complications during support with a ventricular assist system (VAS) can cause severe morbidity and mortality, affecting nearly one-half of all VAS recipients. Because of the lack of a uniform definition of infection, the incidence of this complication is hard to determine accurately. It is approximately 50% for patients being supported by an implantable VAS as a bridge to heart transplantation and 28% for patients supported by an external, short-term VAS. Infections can be classified according to the involvement or noninvolvement of the implanted device and according to the severity of the infection. Severe infections involving the implanted device may preclude heart transplantation for some patients, but numerous patients with milder infections have undergone successful transplantation. Numerous factors predispose VAS patients to infection. Postoperative bleeding necessitating re-operation is an important contributing factor. Endotracheal tubes, intravascular catheters, and other indwelling tubes necessary for the care of postsurgical patients are also common routes of contamination. Control of infection may be improved with new VAS designs, antibiotic impregnated drivelines, and innovative therapies such as antibiotic beads. The next generation of VASs should be inherently less susceptible to infection because of their smaller size, reduced thrombogenicity, and better flow characteristics. In addition to more effective antibiotics, improved VAS designs that incorporate transcutaneous energy transmission systems may reduce infectious complications and allow safe, long-term VAS support.

Evaluation of chlorhexidine and povidone iodine activity against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis using a surface test

Most published studies of the activity of biocides against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) have been based on suspension tests. This study was undertaken to provide information on the effect of chlorhexidine and povidone iodine on bacteria dried on to surfaces, a situation in which biocide activity is known to be reduced. The inactivation of MRSA (10 strains), methicillin-sensitive Staphylococcus aureus (MSSA, 10 strains), VRE (nine strains) and vancomycin-sensitive Enterococcus faecalis (VSE, 10 strains) by 0.5% aqueous chlorhexidine gluconate or 10% povidone iodine was evaluated by applying the European surface test method. Povidone iodine was equally active against resistant and sensitive strains of both species with microbicidal effects (ME), i.e. the log(10)concentration of micro-organisms compared with controls treated with distilled water, after 1.5 min of 3.14 and 3.49 for VRE and VSE respectively, and 3.47 and 3.78 for MRSA and MSSA. Chlorhexidine was equally active against VRE and VSE (ME 3.37 vs. 3. 56 after 7 min, respectively), but was significantly less active against MRSA as opposed to MSSA (ME 3.07 vs. 3.83 after 10 min, P= 0. 017).

Reducing central venous catheter infections

This article reviews the current literature in relation to the management of central venous catheters and the prevention of catheter related infection. Sources and factors influencing catheter related infection are reviewed. In some areas of catheter management, there are clear recommendations such as the choice of skin preparation and catheter site. Other areas don't have clear guidelines; this results in varying practices and the need for further research. The latest research has been in the areas of impregnated catheters with studies showing some benefits. Recent research has also analysed the effect of the method of fluid and line changes as well as their frequency in relation to catheter related infections. A summary is given outlining interventions which have evidence supporting their practice in the reduction of catheter related infections along with interventions which may be effective in reducing catheter related infection and the need for further research.