Role of antimicrobial central venous catheters for the prevention of associated infections

S-Nitroso-N-acetylpenicillamine impregnated latex: A new class of barrier contraception for the prevention of intercourse-associated UTIs

Urinary tract infections (UTIs) are some of the most common infections seen in humans, affecting over half of the female population. Though easily and quickly treatable, if gone untreated for too long, UTIs can lead to narrowing of the urethra as well as bladder and kidney infections. Due to the disease potential, it is crucial to mitigate the development of UTIs throughout healthcare. Unfortunately, sexual activity and the use of condoms have been identified as common risk factors for the development of sexually acquired UTIs. Therefore, this study outlines a potential alteration to existing condom technology to decrease the risk of developing sexually acquired UTIs using S-nitroso-N-acetylpenicillamine (SNAP), a nitric oxide (NO) donor. Herein, varying concentrations of SNAP are integrated into commercialized condoms through a facile solvent swelling method. Physical characterization studies showed that 72%-100% of the ultimate tensile strength was maintained with lower SNAP concentrations, validating the modified condom's mechanical integrity. Additionally, the evaluation of room-temperature storage stability via NO release analysis outlined a lack of special storage conditions needed compared to commercial products. Moreover, these samples exhibited >90% relative cell viability and >96% bacterial killing, proving biocompatibility and antimicrobial properties. SNAP-Latex maintains the desired condom durability while demonstrating excellent potential as an effective new contraceptive technology to mitigate the occurrence of sexually acquired UTIs.

S-Nitroso-N-acetylpenicillamine (SNAP) Impregnated Silicone Foley Catheters: A Potential Biomaterial/Device To Prevent Catheter-Associated Urinary Tract Infections

Urinary Foley catheters are utilized for management of hospitalized patients and are associated with high rates of urinary tract infections (UTIs). Nitric oxide (NO) potently inhibits microbial biofilm formation, which is the primary cause of catheter associated UTIs (CAUTIs). Herein, commercial silicone Foley catheters are impregnated via a solvent swelling method with S-nitroso-N-acetyl-D-penicillamine (SNAP), a synthetic NO donor that exhibits long-term NO release and stability when incorporated into low water-uptake polymers. The proposed catheters generate NO surface-fluxes >0.7 × 10^–10 mol min^–1 cm^–2 for over one month under physiological conditions, with minimal SNAP leaching. These biomedical devices are demonstrated to significantly decrease formation of biofilm on the surface of the catheter tubings over 3, 7, and 14 day periods by microbial species (Staphylococcus epidermidis and Proteus mirabilis) commonly causing CAUTIs. Toxicity assessment demonstrates that the SNAP-impregnated catheters are fully biocompatible, as extracts of the catheter tubings score 0 on a 3-point grading scale using an accepted mouse fibroblast cell-line toxicity model. Consequently, SNAP-impregnated silicone Foley catheters can likely provide an efficient strategy to greatly reduce the occurrence of nosocomial CAUTIs.

A pharmacological and toxicological profile of silver as an antimicrobial agent in medical devices

Silver is used widely in wound dressings and medical devices as a broad-spectrum antibiotic. Metallic silver and most inorganic silver compounds ionise in moisture, body fluids, and secretions to release biologically active Ag(+). The ion is absorbed into the systemic circulation from the diet and drinking water, by inhalation and through intraparenteral administration. Percutaneous absorption of Ag(+) through intact or damaged skin is low. Ag(+) binds strongly to metallothionein, albumins, and macroglobulins and is metabolised to all tissues other than the brain and the central nervous system. Silver sulphide or silver selenide precipitates, bound lysosomally in soft tissues, are inert and not associated with an irreversible toxic change. Argyria and argyrosis are the principle effects associated with heavy deposition of insoluble silver precipitates in the dermis and cornea/conjunctiva. Whilst these changes may be profoundly disfiguring and persistent, they are not associated with pathological damage in any tissue. The present paper discusses the mechanisms of absorption and metabolism of silver in the human body, presumed mechanisms of argyria and argyrosis, and the elimination of silver-protein complexes in the bile and urine. Minimum blood silver levels consistent with early signs of argyria or argyrosis are not known. Silver allergy does occur but the extent of the problem is not known. Reference values for silver exposure are discussed.

A randomized controlled evaluation of absorption of silver with the use of silver alginate (Algidex) patches in very low birth weight (VLBW) infants with central lines

OBJECTIVE

To measure systemic silver absorption when using silver-impregnated alginate central catheter dressings in very low birth weight (VLBW) neonates and to monitor blood stream infection.

STUDY DESIGN

Fifty infants were enrolled in a prospective, randomized controlled trial lasting 28 days. Each patient was assigned to standard dressing or silver alginate (Algidex) group. Serum silver concentrations were obtained on day 1, 7, and 28.

RESULT

Significant differences in mean serum silver concentrations for the treatment versus standard dressing group were observed using student's t-test analysis. The silver alginate group had a 45.8% reduction in infection/1000 line days, although too few patients were enrolled to draw meaningful efficacy conclusions about prevention of blood stream infection.

CONCLUSION

Mean serum silver concentrations in the treatment group were significantly higher than controls although below levels anticipated to result in toxicity. A large study evaluating reduced blood stream infections in VLBW infants is warranted.

Critical Observations on the Neurotoxicity of Silver

Silver is a xenobiotic element with no recognized trace metal value in the human body. It is absorbed into the body through the lungs, gastrointestinal tract, mucus membranes of the urinogenital tract, and through the skin, mainly in the form of silver protein complexes. Although silver is metabolized throughout the soft tissues, available evidence from experimental animal studies and human clinical reports has failed to unequivocally establish that it enters tissues of the central nervous system or is a cause of neurotoxic damage. Argyria characterized by deposition of particles of silver sulfide or silver selenide is the principle contraindication for using silver in medical devices or occupationally. This presents discoloration of the skin but is not regarded as a health risk or manifestation of toxicity. No evidence is available to demonstrate the toxic risk of silver to the peripheral nervous system, although silver sulfide deposits have been identified in the region of cutaneous nerves. Transitory silver sulfide deposits seen in the tissues of the blood-brain and blood-CSF barriers are mostly lysosomally bound or deposited on basement membranes or collagen without toxic effect. Silver is mostly excreted from the body in the urine and feces. Further research is indicated to evaluate the role of metal binding proteins including metallothioneins as cytoprotectants for neurological tissue.

Tunnelled Catheters for the Haemodialysis Patient

Haemodialysis depends upon the establishment of a durable means of vascular access. Although the creation of a successful arterio-venous Fistulae (AVF) is the ideal, this is not always possible or practical. Tunnelled catheters play an important role as an interim/bridge technique for emergency access or while an AVF matures, but may be associated with significant morbidity. The aim of this review is to highlight recent evidence based developments in tunnelled catheters, including methods of placement, complications and possible management strategies.

Role of antibiotic prophylaxis for the prevention of intravascular catheter-related infection

Intravascular catheters have become essential tools for the management of patients in modern medical practice, but there are complications. In particular, catheter-related infection remains a major cause of nosocomial infection and primary septicemia. The development of preventive strategies to reduce the incidence of catheter-related infection is an important goal for all health providers. Over recent years, significant advances in prophylactic measures for the prevention of catheter-related infection have been made. This paper reviews strategies based on antibiotic prophylaxis such as systemic administration of antibiotics, application of antibiotic ointments to the skin insertion site as well as catheter flushing with antibiotics, the antibiotic-lock technique and the use of antimicrobial impregnated catheters.

Evidence-based prevention of catheter infection during parenteral nutrition

Parenteral nutrition is a risk factor for catheter-related bloodstream infection. Here we reviewed strategies for the prevention of catheter-related infections, which always must begin with the cornerstone of prevention: the strict adherence to aseptic techniques. Most research has been interested in coated catheters. From these results, it may be concluded that antibiotics or antiseptic-impregnated catheters, like those with minocycline-rifampicin or chlorhexidine/silver sulfadiazine, significantly reduce catheter-related blood stream infections. Antibiotics or antiseptic-impregnated central venous catheters may even result in cost saving in intensive care units. Antiseptic or antibiotic-lock techniques would also be of interest to prevent catheter-related sepsis in high-risk patients who are receiving parenteral nutrition.

Intravenous access: related problems in oncology

This article reviews the latest developments in the literature concerning two types of catheter widely used in oncology: Hickman central venous catheters (CVCs) and totally implanted venous ports. It now seems possible to diagnose catheter-related bloodstream infections (CRBI) without removing the device; recent studies showed that paired quantitative blood cultures are the most reliable and convenient method for diagnosis of CRBI. Can CRBI be cured and treated without device removal? A decision-tree/flow-chart resulting from analysis of international data by French International Experts is presented. Futures trends are reviewed: new techniques for prevention, including catheters impregnated with antimicrobials and, antiseptic hubs; flushing and antibiotic lock techniques that can be used both for prevention and treatment.

Can we achieve consensus on central venous catheter-related infections?

Central venous catheter-related bacteraemia is a substantial and preventable source of iatrogenic morbidity and mortality. A single episode of catheter-related bacteraemia has an estimated cost of A$50,000, with an attributable mortality between 10 and 35%. Catheter colonization is diagnosed with standard culture techniques. Diagnostic criteria for catheter-related bacteraemia include the results of cultures from the catheter tip, the peripheral blood and other possible sites of infection. The presence of clinical symptoms and subsequent defervescence may assist in making the diagnosis. This review explores the existing definitions of catheter-related infections and proposes a new and more rigorous classification with criteria for definite, probable and possible catheter-related bacteraemia. The authors hope that this classification will enhance the interpretation of the literature and the planning of new investigations. Infection rates can be reduced by appropriate site selection, adequate skin preparation, sterile technique and appropriate dressings. Decreased manipulation of administration sets, with more careful technique and less frequent set replacement, may reduce hub contamination. Infection rates increase with the duration in situ of the catheter, however are not reduced by regular scheduled catheter replacement or guide-wire exchanges. A range of antimicrobial catheter materials and coatings are under investigation, some of which are effective in reducing the rate of catheter-related bacteraemia. Chorhexidine-silver sulphadiazine and rifampicin-minocycline are the best studied combinations to date. Further developments are expected, although none are likely to be as effective as not inserting or removing the central venous catheter when it is not required.