Impact of catheter antimicrobial coating on species-specific risk of catheter colonization: a meta-analysis

Contaminant-Activated Visible Light Photocatalysis

Pristine titanium dioxide (TiO₂) absorbs ultraviolet light and reflects the entire visible spectrum. This optical response of TiO₂ has found widespread application as white pigments in paper, paints, pharmaceuticals, foods and plastic industries; and as a UV absorber in cosmetics and photocatalysis. However, pristine TiO₂ is considered to be inert under visible light for these applications. Here we show for the first time that a bacterial contaminant (Staphylococcus aureus—a MRSA surrogate) in contact with TiO₂ activates its own photocatalytic degradation under visible light. The present study delineates the critical role of visible light absorption by contaminants and electronic interactions with anatase in photocatalytic degradation using two azo dyes (Mordant Orange and Procion Red) that are highly stable because of their aromaticity. An auxiliary light harvester, polyhydroxy fullerenes, was successfully used to accelerate photocatalytic degradation of contaminants. We designed a contaminant-activated, transparent, photocatalytic coating for common indoor surfaces and conducted a 12-month study that proved the efficacy of the coating in killing bacteria and holding bacterial concentrations generally below the benign threshold. Data collected in parallel with this study showed a substantial reduction in the incidence of infections.

Anti-Candida activity of antimicrobial impregnated central venous catheters

Background

Whenever the rate of central line-associated bloodstream infections (CLABSIs) remains high even after the implementation of preventive strategies, the use of chlorhexidine/silver sulfadiazine (CSS) or minocycline/rifampin (MR)-impregnated central venous catheters (CVCs) is currently recommended. Nevertheless, the efficacy of such CVCs against Candida albicans and other emerging non-albicans spp. has been insufficiently studied. This study aims to compare the activity of CSS and MR-impregnated CVCs against the yeasts most frequently isolated from CLABSIs.

Methods

For biofilm formation assays, type strains and clinical isolates of C. albicans, C. glabrata and C. parapsilosis sensu stricto were used. Segments of standard polyurethane, MR and second-generation CSS-CVCs were tested. The biofilm metabolic activity was measured by a semi-quantitative XTT reduction assay.

Results

CSS catheter segments significantly reduced the biofilm metabolic activity by all tested Candida spp., with inhibition ranging from 60% to 100%. The MR catheter segments promoted C. albicans and C. parapsilosis biofilm formation and exhibited an inconspicuous effect against C. glabrata.

Conclusions

Among the recommended antimicrobial CVCs, CSS-CVCs proved to be superior in the inhibition of biofilm formation by the most frequent yeasts causing CLABSIs. Data from this in vitro study may suggest that patients at high risk for invasive candidosis could benefit from the use of CSS-CVCs.

Minocycline Inhibits Candida albicans Budded-to-Hyphal-Form Transition and Biofilm Formation

Candida albicans frequently causes bloodstream infections; its budded-to-hyphalform transition (BHT) and biofilm formation are major contributors to virulence. During an analysis of antibacterial compounds that inhibit C. albicans BHT, we found that the tetracycline derivative minocycline inhibited BHT and subsequent biofilm formation. Minocycline decreased expression of hypha-specific genes HWP1 and ECE1, and adhesion factor gene ALS3 of C. albicans. In addition, minocycline decreased cell surface hydrophobicity and the extracellular β-glucan level in biofilms. Minocycline has been widely used for catheter antibiotic lock therapy to prevent bacterial infection; this compound may also be prophylactically effective against Candida infection.

Drug eluting antimicrobial vascular catheters: Progress and promise

Vascular catheters are critical tools in modern healthcare yet present substantial risks of serious bloodstream infections that exact significant health and economic burdens. Drug-eluting antimicrobial vascular catheters have become important tools in preventing catheter-related bloodstream infections and their importance is expected to increase as significant initiatives are expanded to eliminate and make the occurrence of these infections unacceptable. Here we review clinically significant and emerging drug-eluting antimicrobial catheters within the categories of antibiotic, antiseptic, novel bioactive agents and energy-enhanced drug eluting antimicrobial catheters. Important representatives of each category are reviewed from the standpoints of mechanisms of action, physical-chemical properties, safety, in vitro and clinical effectiveness.

An engineered micropattern to reduce bacterial colonization, platelet adhesion and fibrin sheath formation for improved biocompatibility of central venous catheters

Background

Catheter-related bloodstream infections (CRBSIs) and catheter-related thrombosis (CRT) are common complications of central venous catheters (CVC), which are used to monitor patient health and deliver medications. CVCs are subject to protein adsorption and platelet adhesion as well as colonization by the natural skin flora (i.e. Staphylococcus aureus and Staphylococcus epidermidis). Antimicrobial and antithrombotic drugs can prevent infections and thrombosis-related complications, but have associated resistance and safety risks. Surface topographies have shown promise in limiting platelet and bacterial adhesion, so it was hypothesized that an engineered Sharklet micropattern, inspired by shark-skin, may provide a combined approach as it has wide reaching anti-fouling capabilities. To assess the feasibility for this micropattern to improve CVC-related healthcare outcomes, bacterial colonization and platelet interactions were analyzed in vitro on a material common for vascular access devices.

Methods

To evaluate bacterial inhibition after simulated vascular exposure, micropatterned thermoplastic polyurethane surfaces were preconditioned with blood proteins in vitro then subjected to a bacterial challenge for 1 and 18 h. Platelet adhesion was assessed with fluorescent microscopy after incubation of the surfaces with platelet-rich plasma (PRP) supplemented with calcium. Platelet activation was further assessed by monitoring fibrin formation with fluorescent microscopy after exposure of the surfaces to platelet-rich plasma (PRP) supplemented with calcium in a flow-cell. Results are reported as percent reductions and significance is based on t-tests and ANOVA models of log reductions. All experiments were replicated at least three times.

Results

Blood and serum conditioned micropatterned surfaces reduced 18 h S. aureus and S. epidermidis colonization by 70% (p ≤ 0.05) and 71% (p < 0.01), respectively, when compared to preconditioned unpatterned controls. Additionally, platelet adhesion and fibrin sheath formation were reduced by 86% and 80% (p < 0.05), respectively, on the micropattern, when compared to controls.

Conclusions

The Sharklet micropattern, in a CVC-relevant thermoplastic polyurethane, significantly reduced bacterial colonization and relevant platelet interactions after simulated vascular exposure. These results suggest that the incorporation of the Sharklet micropattern on the surface of a CVC may inhibit the initial events that lead to CRBSI and CRT.

Gold nanoshell-decorated silicone surfaces for the near-infrared (NIR) photothermal destruction of the pathogenic bacterium E. faecalis

Catheter-related infections (CRIs) are associated with the formation of pathogenic biofilms on the surfaces of silicone catheters, which are ubiquitous in medicine. These biofilms provide protection against antimicrobial agents and facilitate the development of bacterial resistance to antibiotics. The application of photothermal agents on catheter surfaces is an innovative approach to overcoming biofilm-generated CRIs. Gold nanoshells (AuNSs) represent a promising photothermal tool, because they can be used to generate heat upon exposure to near-infrared (NIR) radiation, are biologically inert at physiological temperatures, and can be engineered for the photothermal ablation of cells and tissue. In this study, AuNSs functionalized with carboxylate-terminated organosulfur ligands were attached to model catheter surfaces and tested for their effectiveness at killing adhered Enterococcus faecalis (E. faecalis) bacteria. The morphology of the AuNSs was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), while the elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Furthermore, optical and photothermal properties were acquired by ultraviolet-visible (UV-vis) spectroscopy and thermographic imaging with an infrared camera, respectively. Bacterial survival studies on AuNS-modified surfaces irradiated with and without NIR light were evaluated using a colony-formation assay. These studies demonstrated that AuNS-modified surfaces, when illuminated with NIR light, can effectively kill E. faecalis on silicone surfaces.

Taurolidine lock solutions for the prevention of catheter-related bloodstream infections: a systematic review and meta-analysis of randomized controlled trials

Background

Catheter-related bloodstream infections (CRBSIs) are a significant cause of morbidity and mortality in critically ill patients, contributing to prolonged hospital stays and increased costs. Whether taurolidine lock solutions (TLS) are beneficial for the prevention of CRBSIs remains controversial. In this meta-analysis, we aim to assess the efficacy of TLS for preventing CRBSIs.

Methods

We conducted a systematic search of PubMed, EMBASE, and the Cochrane Central Register of Controlled Trials. Eligible studies included randomized controlled trials that reported on the effects of TLS for preventing CRBSIs. The primary outcome in these studies was catheter-related bloodstream infections, with microbial distribution of CRBSI and catheter-associated thrombosis as secondary outcomes. Data were combined using random-effects models owing to significant clinical heterogeneity.

Results

Six randomized controlled trials (RCTs) conducted from 2004 through 2013 involving 431 patients and 86,078 catheter-days were included in the review. TLS were significantly associated with a lower incidence of CRBSIs when compared to heparin lock solutions (Risk Ratio [RR], 0.34; 95% Confidence Interval [CI], 0.21–0.55). Use of TLS significantly decreased the incidence of CRBSIs from gram-negative (G−) bacteria (P = 0.004; RR, 0.27; CI, 0.11–0.65), and was associated with a non-significant decrease in gram-positive (G+) bacterial infections (P = 0.07; RR, 0.41; CI, 0.15–1.09). No significant association was observed with TLS and catheter-associated thrombosis (RR, 1.99; CI, 0.75–5.28).

Conclusions

The use of TLS reduced the incidence of CRBSIs without obvious adverse effects or bacterial resistance. However, the susceptibility of G+ and G- bacteria to taurolidine and the risk for catheter-associated thrombosis of TLS are indeterminate due to limited data. The results should be treated with caution due to the limited sample sizes and methodological deficiencies of included studies. Therefore, additional well-designed and adequately powered RCTs are needed to confirm these findings.