A large randomized clinical trial of a silver-impregnated urinary catheter: lack of efficacy and staphylococcal superinfection

Catheter-associated urinary tract infections: new aspects of novel urinary catheters

Nosocomial urinary tract infection is the most common infection acquired both in hospitals and nursing homes and is usually associated with catheterisation. These catheter-associated urinary tract infections (CAUTIs) have been reported to increase mortality and have a considerable economic impact. To date, the sole effective preventative strategy is the use of a closed drainage system and removal of the catheter as soon as possible. The underlying cause of CAUTI is the formation of a pathogenic biofilm on the surface of the indwelling urinary catheter. Currently, researchers seek to alter the catheter surface in order to inhibit biofilm formation. Many substances are being studied for their potential as biofilm-disrupting catheter coatings. Among these substances, recently developed antibiotic-coated catheters may provide promise for the control of CAUTI. More basic research at the level of pathogenesis and catheter substance is needed to design novel strategies.

Risks of long-term catheterization in the community--and managing them

Catheter-associated urinary tract infections continue to be a major source of morbidity in hospital and the community. In part, this may be the result of ritualistic practices, compounded by poor communication on discharge from hospital. This article highlights many of the issues that lead to continued high rates of CAUTI, and challenges health professionals and health-care providers to use all available guidance and tools to reduce the incidence of CAUTI across the NHS.

Evidence for the use of silver-alloy-coated urethral catheters

Catheter-associated urinary tract infections (CAUTIs) are a common occurrence and are associated with increased patient morbidity and mortality. In addition, they delay patient discharge from hospital, substantially increase hospital costs and promote the emergence of resistant organisms. Any intervention resulting in a decrease in the incidence of CAUTIs would have a significant impact on patient quality of life and hospital costs. By reviewing the current literature, it can be seen that the use of silver-alloy-coated hydrogel catheters can reduce CAUTIs by up to 45%. Despite reducing CAUTIs in most hospital situations, the greatest reduction is seen in postoperative patients, intensive care unit patients and burns patients.

Health-Care–Associated Infections and Prevention

Health-care-associated infections (HAIs) are an important cause of perioperative morbidity and mortality. Currently, one out of every 10 surgical patients develops an HAI. Causes of HAIs vary, but include the transient immunodeficiency associated with surgery,immobility, and the presence of indwelling devices. With rates of antimicrobial resistance increasing, prevention remains the best solution. The investigators review the most frequently encountered health-care-associated infections with an emphasis on preventative strategies. The article addresses issues related to the diagnosis,treatment, and prevention of health-care-related pneumonia,health-care-associated urinary tract infections, and intravascular-catheter-related infections. The article also discusses the utility of hand hygiene policies.

Antimicrobial effect of surgical masks coated with nanoparticles

This study assessed the antimicrobial activity of nanoparticles (consisting of a mixture of silver nitrate and titanium dioxide) and nanoparticle-coated facemasks to protect against infectious agents. The minimum inhibitory concentrations of the nanoparticles against Escherichia coli and Staphylococcus aureus were 1/128 and 1/512, respectively. The antibacterial activity of nanoparticle-coated masks was quantified according to the procedures of AATCC 100-1999. A 100% reduction in viable E. coli and S. aureus was observed in the coated mask materials after 48 h of incubation. Skin irritation was not observed in any of the volunteers who wore the facemasks. Nanoparticles show promise when applied as a coating to the surface of protective clothing in reducing the risk of transmission of infectious agents.

Materials for urinary catheters: a review of their history and development in the UK

The Foley catheter, introduced in the mid-1930s and originally manufactured from latex, is still the most commonly used device for the management of urinary incontinence (UI). Despite the passage of time, there are still problems associated with the use of these devices. It is currently estimated that the management and treatment of UI costs the UK National Health Service (NHS) in the order of 500 million pound per annum. Faced with the known demographic changes in the adult population these costs will continue to rise for the foreseeable future. This review examines the range of materials currently used to manufacture Foley catheters from both latex and silicone. It outlines the common problems associated with their clinical use-infection, encrustation and blockage. The main changes that have been made to the materials employed in response to these problems are analysed. In the first instance the use of controlled release glass and slow release polymers to introduce disinfectants and antibacterial agents is considered. Attempts to alter surface properties by using coatings based on silver, polytetrafluoroethylene (PTFE), hydrogels and silicone are then described. It can be seen that despite these approaches, problems remain with the design and materials currently used to manufacture catheters. The review concludes that changes to the materials currently used for the manufacture of commercially available catheters could potentially alleviate many of the existing problems. However, standards need to be developed in order to enable direct comparison of the mechanical and physical properties of existing and potential catheter designs to ensure their effective function in-service.

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

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

BisEDT and RIP act in synergy to prevent graft infections by resistant staphylococci

Staphylococci are a major cause of infections associated with indwelling medical devices. Biofilm formation on these devices adds to the antibiotic resistance seen among clinical isolates. RNAIII-inhibiting peptide (RIP) is a heptapeptide that inhibits staphylococcal pathogenesis, including biofilm formation, by obstructing quorum sensing mechanisms. Bismuth ethanedithiol (BisEDT) also prevents biofilm formation at subinhibitory concentrations. RIP and BisEDT were combined to prevent infections in a rat graft model, using antibiotic sensitive and resistant strains of Staphylococcus aureus and Staphylococcus epidermidis. BisEDT, RIP, or rifampin, or their combinations reduced the graft associated bacterial load over seven days. BisEDT-RIP was the best combination, reducing bacterial load to undetectable levels. BisEDT-RIP may prove useful for coating medical devices to prevent staphylococcal infections.

A rapid method of impregnating endotracheal tubes and urinary catheters with gendine: a novel antiseptic agent

OBJECTIVES

To test the efficacy of gendine, a novel antiseptic, containing Gentian Violet and chlorhexidine, in coating different medical devices, including endotracheal tubes (ETT) and urinary catheters (UC).

METHODS

We determined the antimicrobial efficacy and cytotoxicity of ETT and UC segments coated, through an instant dip method, with gendine. Using the modified Kirby-Bauer method, gendine-coated devices showed zones of inhibition of >/=15 mm against methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa, Escherichia coli and Candida parapsilosis.

RESULTS

Gendine-coated endotracheal tubes (GND-ETT) soaked in bronchoalveolar fluid (BAL) and incubated at 37 degrees C maintained a zone of inhibition of >/=15 mm against MRSA and P. aeruginosa for at least 3 weeks. Similarly, gendine-coated urinary catheters (GND-UC), soaked in urine, maintained a zone of inhibition of >/=15 mm against E. coli for 8 weeks. Using the minimum essential media elution method in mouse fibroblast cells, GND-ETT and GND-UC were found to be non-cytotoxic. Gendine-coated UC significantly reduced the amount of viable MRSA, E. coli or C. parapsilosis organisms adhering to their surfaces when compared with silver/hydrogel-coated urinary catheters or control uncoated catheters (P < 0.01). Similarly GND-ETT significantly reduced the adherence of the same organisms as well as P. aeruginosa when compared with control (P </= 0.02).

CONCLUSIONS

GND-ETT and GND-UC impregnated using an instantaneous dip method, were shown to have broad-spectrum activity, prolonged antimicrobial durability and high efficacy in inhibiting adherence of organisms commonly causing nosocomial pneumonia and urinary tract infection. Furthermore, these coated devices were shown to be non-cytotoxic.

Silver nanoparticles and polymeric medical devices: a new approach to prevention of infection?

OBJECTIVES

Implantable devices are major risk factors for hospital-acquired infection. Biomaterials coated with silver oxide or silver alloy have all been used in attempts to reduce infection, in most cases with controversial or disappointing clinical results. We have developed a completely new approach using supercritical carbon dioxide to impregnate silicone with nanoparticulate silver metal. This study aimed to evaluate the impregnated polymer for antimicrobial activity.

METHODS

After impregnation the nature of the impregnation was determined by transmission electron microscopy. Two series of polymer discs were then tested, one washed in deionized water and the other unwashed. In each series, half of the discs were coated with a plasma protein conditioning film. The serial plate transfer test was used as a screen for persisting activity. Bacterial adherence to the polymers and the rate of kill, and effect on planktonic bacteria were measured by chemiluminescence and viable counts. Release rates of silver ions from the polymers in the presence and absence of plasma was measured using inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Tests for antimicrobial activity under various conditions showed mixed results, explained by the modes and rates of release of silver ions. While washing removed much of the initial activity there was continued release of silver ions. Unexpectedly, this was not blocked by conditioning film.

CONCLUSIONS

The methodology allows for the first time silver impregnation (as opposed to coating) of medical polymers and promises to lead to an antimicrobial biomaterial whose activity is not restricted by increasing antibiotic resistance.

A pilot randomized double-blind placebo-controlled trial on the use of antibiotics on urinary catheter removal to reduce the rate of urinary tract infection: the pitfalls of ciprofloxacin

OBJECTIVE

To assess if a short course of antibiotics starting at the time of the removing a short-term urethral catheter decreases the incidence of subsequent urinary tract infection (UTI).

PATIENTS AND METHODS

Patients across specialities with a urethral catheter in situ for >/= 48 h and </= 7 days were recruited at the time of catheter removal. Patients were excluded if they had had recent genitourinary surgery or were on antibiotics. Eligible patients were randomly assigned to a 48-h course of either ciprofloxacin or placebo tablets starting 2 h before catheter removal. A catheter specimen of urine was obtained before the start of the trial medication. The follow-up was at 7 and 14 days after catheter removal, with a questionnaire for UTI symptoms, and a mid-stream urine sample was taken.

RESULTS

Forty-eight patients were recruited and had a complete follow-up (25 received ciprofloxacin and 23 placebo). Of the ciprofloxacin group, four patients (16%) had a UTI at the follow-up after catheter removal, and two were symptomatic. The UTI in two patients (including one of those symptomatic) was newly developed after catheter removal; the other two UTIs were a result of failure to resolve a catheter-associated UTI. All these UTIs in the ciprofloxacin group were resistant to ciprofloxacin. Of the placebo group, three patients (13%) had a UTI at the follow-up after removal, and one patient was symptomatic. The UTI, newly developed after catheter removal, was resistant to ciprofloxacin. The other two patients were asymptomatic; their UTIs were a result of failure to resolve a catheter-associated UTI, and one was resistant to ciprofloxacin.

CONCLUSIONS

The risk of UTI (both symptomatic and asymptomatic) after removing a urethral catheter is real, even in absence of catheter-associated UTI before removal. UTIs occurring after removing a short-term urinary catheter had a high rate of resistance to ciprofloxacin. There was no detectable significant benefit in using prophylactic ciprofloxacin to reduce the UTI rate after catheter removal.

A comparative multicentre study on the incidence of catheter-associated urinary tract infection between nitrofurazone-coated and silicone catheters

The efficacy of nitrofurazone-coated urinary catheter in inhibitory activity of catheter-associated urinary tract infection (CAUTI) was evaluated. The incidence rate and onset of CAUTI after catheterisation of standard silicone urinary catheters and nitrofurazone-coated catheters was compared. There was no statistical significance between the two groups in the incidence rate of CAUTI. However, in patients who had indwelling urinary catheters for 5-7 days, the incidence rate of CAUTI was significantly lower in the experimental group. Logistic regression analysis showed that the two variables, including age and period of insertion, affected the incidence rate of CAUTI significantly. Nitrofurazone-coated catheters can be useful for inhibition of CAUTI in patients who have indwelling urinary catheter for 5-7 days and in old-age patients.

Catheter-associated urinary tract infections in intensive care units

The purpose of this review is to analyze literature concerning the diagnosis, prevention, and management of catheter-associated urinary tract infection (CAUTI) occurring in patients hospitalized in the intensive care unit (ICU). Analysis was performed from personal and "Pubmed" data, crossing the following keywords: "urinary tract infection", "catheter', and "intensive care unit". Few clinical trials including ICU patients were found despite the abundance of expert opinions. There is no consensus on the use of urinary reagent tests for diagnosis. The prevention of CAUTI in ICU patients does not require expensive devices. Neither complex closed drainage systems nor silver-coated urinary catheters have demonstrated efficacy in comparative randomized clinical trials. Bladder irrigation should not be used, except when an obstruction of the catheter is highly likely. The administration of prophylactic antimicrobial therapy, although effective in reducing the incidence of urinary bacteria, cannot be recommended in ICU patients. The management of CAUTI in ICU patients has not been evaluated in clinical trials. The level of evidence provided in this field is weak, and underlines the need for randomized studies to improve management of patients.

Catheter-associated urinary tract infections: diagnosis and prophylaxis

Catheter-associated urinary tract infections (CAUTI) are the commonest nosocomial infections worldwide. While they are often asymptomatic and frequently cost less than nosocomial surgical site infections or nosocomial pneumonia, they are major reservoirs of antimicrobial resistant pathogens. Numerous strategies have been devised in an attempt to reduce the incidence of CAUTI but few have proven effective. Novel technologies such as the potential use of antiseptic or antimicrobial coatings on catheters hold promise for possibly reducing these infections in the fight against antimicrobial resistance.

Surface-grafted viologen for precipitation of silver nanoparticles and their combined bactericidal activities

A viologen, N-hexyl-N'-(4-vinylbenzyl)-4,4'-bipyridinium dinitrate (HVVN), was synthesized and subsequently graft-copolymerized on poly(ethylene terephthalate) (PET) films. Silver nanoparticles can be deposited on the surface of the HVVN-PET film through photoinduced reduction of the silver ions in salt solution. The size and distribution of the silver nanoparticles can be varied by changing the reaction time. The pyridinium groups of the HVVN graft-copolymerized on the surface of the substrate possess bactericidal effects on Escherichia coli, and this antibacterial effect can be very significantly enhanced by the incorporation of silver nanoparticles on the HVVN-PET film. The dual functionalities of HVVN and silver remain stable after prolonged immersion in phosphate buffer solution and after aging in a weathering chamber.

Prevention of catheter-related infections: the potential of a new nano-silver impregnated catheter

Contaminated or infected catheters are a major source of nosocomial infections responsible for >40% of all episodes of nosocomial sepsis in acute-care hospitals. Antibiotics as well as surface modifications with, for example, hydrogels proved to be of little value in preventing the contamination of indwelling catheters. The even distribution of 10(12-13) activated silver nanoparticles per gram in various polymers, e.g. polyurethane and silicone, results in an excellent antimicrobial activity against a broad spectrum of organisms in vitro. Substantial reduction of incrustation of these catheters was also observed. These preliminary experimental data warrant clinical studies.

Types of urethral catheters for management of short-term voiding problems in hospitalised adults

BACKGROUND

Urinary tract infection is the most common hospital acquired infection. The major associated cause is indwelling urinary catheters. Currently there are many types of catheters available. A variety of specialised urethral catheters have been designed to reduce the risk of infection. These include antiseptic impregnated catheters and antibiotic impregnated catheters. Other issues that should be considered when choosing a catheter are ease of use, comfort and the cost.

OBJECTIVES

The primary objective of this review was to determine the effect of type of indwelling urethral catheter on the risk of urinary tract infection in adults who undergo short-term urinary catheterisation.

SEARCH STRATEGY

We searched the specialised trials registers of the Cochrane Incontinence Group (November 2003) and the Cochrane Renal Group (February 2003). We also examined the bibliographies of relevant articles and contacted catheter manufacturer representatives for trials.

SELECTION CRITERIA

All randomised and quasi randomised trials comparing types of indwelling urinary catheters for short-term catheterisation in hospitalised adults. Short-term catheterisation was defined as up to and including fourteen days, or other temporary short-term use as defined by the trialists.

DATA COLLECTION AND ANALYSIS

Data were extracted by one reviewer and independently verified by a second reviewer. Disagreements were resolved by discussion. Data were processed as described in the Cochrane Handbook. Where data in trials were not fully reported, clarification was sought directly from the trialists (secondary sources were used to confirm results of one trial).

MAIN RESULTS

Eighteen trials met the inclusion criteria involving 4237 hospitalised adults in 17 parallel group trials and 27,878 adults in one large cluster-randomised cross-over trial. Only three of the possible six comparisons were addressed in these trials: antiseptic impregnated catheters versus standard catheters (n=11 trials), antibiotic impregnated catheters versus standard catheters (n=1 trial) and comparison of different standard catheters (n=6 trials). The results of the antiseptic versus standard catheter trials differed according to the antiseptic used to impregnate the catheter. The antiseptic catheters were either impregnated with silver oxide or silver alloy. Silver oxide catheters were not associated with a statistically significant reduction in bacteriuria in short-term catheterised hospitalised adults but the confidence intervals were wide (RR 0.89, 95% CI 0.68 to 1.15). Silver alloy catheters were found to significantly reduce the incidence of asymptomatic bacteriuria (RR 0.36, 95% CI 0.24 to 0.52) in hospitalised adults catheterised for less than one week. At greater than one week catheterisation the risk of asymptomatic bacteriuria was still reduced with the use of silver alloy catheters (RR 0.67, 95% CI 0.50 to 0.90). The risk of symptomatic urinary tract infection was also found to be reduced with the use of silver alloy catheters (RR 0.60, 95% CI 0.50 to 0.73). The randomised cross-over trial of silver alloy catheters versus standard catheters was excluded from the pooled results because data were not available prior to crossover. The results of this trial indicated benefit from the silver alloy catheters and included an economic analysis that indicated cost savings of between 3.3 per cent and 35.5 per cent. One small trial investigated men post radical prostatectomy catheterised with antibiotic impregnated catheter versus standard catheters and found a lower rate of asymptomatic bacteriuria in the antibiotic group at less than one week of catheterisation (RR 0.36, 95% CI 0.18 to 0.73). The trial at less than one week found that the risk of bacteriuria was also less in the antibiotic impregnated catheter group (RR 0.36, 95% CI 0.18 to 0.73); however, at greater than one week the result was not significant (RR 0.94, 95% CI 0.86 to 1.03). One of 56 men in the antibiotic impregnated group had a symptomatic UTI compared with 6 of 68 who had standard catheters (RR 0.20, 9h 6 of 68 who had standard catheters (RR 0.20, 95% CI 0.03 to 1.63). Three trials compared two different types of standard catheters (defined as catheters that are not impregnated with antiseptics or antibiotics) to investigate infection but the results were not pooled because of the clinical and statistical heterogeneity between trials. Individual findings of the trials did not show whether or not one type of standard catheter reduced the risk of catheter related urinary tract infection compared to another type of standard catheter. Another three trials compared different types of standard catheters to investigate for adverse urethral effects in catheterised men. Once again the trials were not pooled due to significant heterogeneity; however, the results of the individual trials indicate a trend toward silicone catheters being less likely to result in adverse urethral effects in men.

REVIEWER'S CONCLUSIONS

The results suggest that the use of silver alloy indwelling catheters for catheterising hospitalised adults short-term reduces the risk of catheter acquired urinary tract infection. Further economic evaluation is required to confirm that the reduction of infection compensates for the increased cost of silver alloy catheters.Catheters coated with a combination of minocycline and rifampin may also be beneficial in reducing bacteriuria in hospitalised men catheterised less than one week but this requires further testing. There was not enough evidence to suggest whether or not any standard catheter was better than another in terms of reducing the risk of urinary tract infection in hospitalised adults catheterised short-term. Siliconised catheters may be less likely to cause urethral side effects in men: however, this result should be interpreted with some caution as the trials were small and the outcome definitions and specific catheters compared varied.

Management of short-term indwelling urethral catheters to prevent urinary tract infections

BACKGROUND

This systematic review updates a previous review published in 2000. The objective of this review was to present the best available evidence relating to the prevention of catheter-associated urinary tract infections (UTI).

SELECTION CRITERIA

This review considered randomised controlled trials (RCTs) of adult patients with short-term urethral catheters. In the absence of RCTs, other research designs such as non-randomised controlled trials and before and after studies were considered for inclusion. Interventions of interest were those related to the prevention of catheter-related UTI and included: sterile versus non-sterile insertion technique, special coatings to catheters versus standard non-coated catheters, the use of flush solutions, the use of solutions added to urinary drainage bag, maintenance of a closed urinary drainage circuit, the use of antireflux valves, antibiotic creams applied to the external meatus-catheter interface, meatal care regimens, education programs, and changed care delivery practices. This review was limited to short-term urethral catheters, and so studies evaluating long-term or suprapubic catheters were excluded. The primary outcome of interest was the difference in the rates of UTI between experimental intervention and the control.

SEARCH STRATEGY

The search included both published and unpublished studies with an initial limited search of MEDLINE and CINAHL databases undertaken to identify key words contained in the title or abstract, and index terms used to describe relevant interventions. A second extensive search used all identified key words and index terms. The third step included a search of the reference lists and bibliographies of relevant articles. The databases searched included: CINAHL, MEDLINE, Current Contents, Cochrane Library, Expanded Academic Index, and Embase. The Dissertation Abstracts International database was searched for unpublished studies.

ASSESSMENT OF METHODOLOGICAL QUALITY

Methodological quality was assessed using a standardised checklist. Critical appraisal and data extraction were conducted by two independent reviewers; discrepancies were addressed through discussion with a third reviewer as required.

RESULTS

There was no significant difference in infection rate using either sterile surgical or non-sterile insertion technique. The use of water for cleansing prior to catheter insertion was recommended. There was no additional benefit from specific meatal care other than standard daily personal hygiene and removal of debris. Infection rates were similar for both latex and silicone catheters. Comparisons between silver and Teflon coating clearly favoured the silver alloy coating. The use of a complex closed drainage system in the intensive care environment did not confer any additional benefit. Studies comparing types of junction seals and use of junction seals either prior to or following catheterisation found no clear benefit from using either preconnected sealed systems or sealed systems with the addition of silver releasing devices. Neither the addition of chlorhexidine nor hydrogen peroxide to the drainage bag was found to be effective at reducing UTI rates. The findings indicated there was a higher incidence of bacteriuria associated with Foley catheters compared with intermittent catheterisation (P < 0.025). A single RCT examined the effect on UTI rates of routine bag changes against no routine bag change. Routine bag changes were not advantageous in reducing the risk of infection.

CONCLUSIONS

Current RCT evidence suggests the use of a surgical sterile catheterisation technique is not required, and that tap water is sufficient for cleaning genitalia. Following insertion, daily hygiene around the meatal area is as effective as catheter toilets; and catheters impregnated with silver may reduce the incidence of catheter associated bacteriuria. Sealed (e.g. taped, presealed) drainage systems should not be relied upon as the sole mechanism for prevention of bacteriuria. The addition of antibacterial solutions to drainage bags and the routine change of drainage bags had no effect on catheter associated infection. However, most of the recommendations arising from this review were based on single studies, often with limited numbers of participants. There is an urgent need to replicate these studies in other clinical settings.

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.

Asymptomatic bacteriuria: when to screen and when to treat

Asymptomatic bacteriuria is common. Populations with structural or functional abnormalities of the genitourinary tract may have an exceedingly high prevalence of bacteriuria, but even healthy individuals frequently have positive urine cultures. Asymptomatic bacteriuria is seldom associated with adverse outcomes. Pregnant women and individuals who are to undergo traumatic genitourinary interventions are at risk for complications of bacteriuria and benefit from screening and treatment programs. Although screening is recommended for renal transplant recipients, the benefits for these patients are less clear. For other populations, including most bacteriuric individuals, negative outcomes attributable to asymptomatic bacteriuria have not been described. Treatment of asymptomatic bacteriuria in these patients is not beneficial and, in fact, may be associated with harmful outcomes, such as increased short-term frequency of symptomatic infection, adverse drug effects, and reinfection with organisms of increased antimicrobial resistance. Screening for asymptomatic bacteriuria and treatment is recommended for only selected groups where benefit has been shown. Many research questions still need to be addressed. Different populations have unique risk factors, and the benefits and risks of different management approaches for asymptomatic bacteriuria must continue to be addressed systematically in appropriate clinical trials.

Biofilms and catheter-associated urinary tract infections

Urinary catheter-related infections are commonly seen in several different patient populations and lead to substantial morbidity. The overall health care costs caused by these infections are sizable given how often urinary catheters are used in acute care settings, extended care facilities, and in persons with injured spinal cords. Recent attention has appropriately focused on biofilm development on the catheter surface because biofilm has important implications for the pathogenesis, treatment, and prevention of catheter-related infection. Because the most important risk factor for infection is duration of catheterization, indwelling urethral catheterization should be avoided or at least limited whenever possible. Additional methods to prevent this infection include aseptic insertion and maintenance use of a closed drainage system, anti-infective catheters in patients at high-risk for infection, and systemic antibiotics in select patients. Alternative urinary collection strategies may be appropriate in certain patient groups. Specifically, condom catheters should be considered in men likely to be adherent with this urinary collection method, suprapubic catheters should be considered in patients requiring long-term indwelling drainage, and intermittent catheterization seems appropriate in patients with injured spinal cords. Future research should focus on additional methods for preventing this common infection.

Preventing antimicrobial-resistant bacterial infections in surgical patients

BACKGROUND

The Centers for Disease Control and Prevention (CDC) has identified the control of antimicrobial resistance as an important effort to reduce the morbidity and mortality associated with health care. Methods to prevent these infections in surgical patients have rarely been addressed specifically.

METHODS

The peer-reviewed literature and published guidelines were examined to identify proven or suggested techniques for controlling antimicrobial resistance that would be particularly relevant to surgeons and the surgical patient population.

RESULTS

A multi-step approach to the prevention of antimicrobial-resistant infections in surgical patients was developed. This program consists of four major strategies: Infection prevention, effective diagnosis and treatment of infection, optimal antibiotic utilization, and the prevention of transmission.

CONCLUSION

The control of antimicrobial resistance in bacteria is an important objective for all physicians, including surgeons. An approach to attain this goal in surgical populations is outlined. Further research will be needed to determine the value of these practices and to develop newer, even more effective interventions.

Urinary catheter 'deflation cuff' formation: clinical audit and quantitative in vitro analysis

OBJECTIVE

To investigate reports from district nursing staff of difficulty in removing long-term urinary catheters (LTCs) because of the formation of a 'cuff' on deflating the self-retaining balloon.

PATIENTS AND METHODS

Problems experienced by district nurses when removing urethral and suprapubic LTCs were audited, noting the type of problem, the catheter and any action taken. Quantitative in vitro studies were conducted on the deflated self-retaining balloons after incubating a similar range of catheters in saline at 37 degrees C for 6 weeks, using suprapubic profilometry to assess the resistance to withdrawal (retention force).

RESULTS

Questionnaires were returned on 154 patients with LTCs; 56% had urethral and 44% suprapubic catheters. The catheters were hydrogel-coated (83%), all-silicone (13%) and PTFE-coated (3%). Twenty-two (14%) of the sample reported problems with catheter removal in the previous year, including 15 (68%) with all-silicone catheters and 15 (68%) with suprapubic catheters; cuff formation was noted in 60%. In the laboratory, 10 of the balloons formed a 'cuff' on deflation, but there was great variability in the effect this had on the retention force, with values of 0.5-3 N for different catheters.

CONCLUSIONS

Most problems with catheter removal involved all-silicone and suprapubic catheters. Suprapubic profilometry confirmed increased resistance to withdrawal by formation of a 'cuff' on deflation of the balloon of all-silicone catheters. These results suggest that the first choice of catheter material for long-term urethral and suprapubic use should be hydrogel-coated latex.

Is there evidence for recommending silver-coated urinary catheters in guidelines?

We evaluated the available literature on effectiveness of silver-coated versus uncoated catheters for the prevention of urinary tract infections in catheterized patients stratified by sex, systemic antibiotic use, renal function and duration of catheterization. Controlled clinical trials, randomized clinical trials and systematic reviews/meta-analysis were identified by a search strategy in Medline (1966-August 2001) and in the Cochrane Controlled Trials Register. Keywords were urinary catheterization, silver and infection. Trials using silver-coated catheters in the treatment group and uncoated catheters in the control group, with bacteriuria as the outcome measure, were selected. The quality of the methods used of all selected publications was assessed by using a quality assessment scale for randomized clinical trials. In addition we looked critically at subject-specific aspects. Data from the original publications were used to calculate the overall relative risk of bacteriuria in patients with silver-coated versus uncoated catheters, as well as the effect in subgroups. Thirteen trials and one meta-analysis were identified. Seven reports satisfied the selection criteria with only one achieving a high-quality score. Confounding variables were not considered in any trial. Additional studies with a high standard of internal quality and careful specification of the clinical question with regard to subject-specific critical points are necessary to decide whether the use of silver-coated catheters can be recommended.

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.

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

AIMS

To compare the number of attached Shewanella putrefaciens on stainless steel with different silver surfaces, thus evaluating whether silver surfaces could contribute to a higher hygienic status in the food industry.

METHODS AND RESULTS

Bacterial adhesion to three types of silver surface (new silver, tarnished silver and sulphide-treated silver) was compared with adhesion to stainless steel (AISI 316) using the Malthus indirect conductance method to estimate the number of cfu cm(-2). The number of attached bacteria on new silver surfaces was lower than on steel for samples taken after 24 h. However, this was not statistically significant (P > 0.05). The numbers of attached bacteria were consistently lower when tarnished silver surfaces were compared with stainless steel and some, but not all, experiments showed statistical significance (P < 0.05). Treating new silver with sulphide to reproduce a tarnished silver surface did not result in a similar lowering of adhering cells when compared with steel (P > 0.05).

CONCLUSIONS

New or tarnished silver surfaces caused a slight reduction in numbers of attached bacteria; however, the difference was only sometimes statistically significant.

SIGNIFICANCE AND IMPACT OF THE STUDY

The lack of reproducibility in differences in numbers adhering to the different surfaces and lack of statistical significance between numbers of adhered viable bacteria do not indicate that the tested silver surfaces can be used to improve hygienic characteristics of surfaces in the food industry.

Use of silver-hydrogel urinary catheters on the incidence of catheter-associated urinary tract infections in hospitalized patients

BACKGROUND

Urinary tract infections (UTIs) account for 40% of all nosocomial infections, and about 80% of these are associated with the use of urinary catheters. They not only contribute to excess morbidity and mortality, but they also significantly add to the cost of hospitalization. Clinical trials with silver-coated urinary catheters have shown conflicting results. However, recent trials with silver-hydrogel urinary catheters have shown a reduction in nosocomial UTIs, and these catheters appear to offer cost savings.

METHOD

The University of Massachusetts Medical Center is a teaching, tertiary hospital with 18% of its beds in intensive care units. The silver-hydrogel urinary catheters were introduced in October 1997. The rate of catheter-associated UTIs with silver-hydrogel urinary catheter use was compared with a historical baseline UTI rate that was established for January 1996 and January 1997 with the standard, noncoated catheters. The cost of a nosocomial catheter-associated UTI was estimated by calculating the hospital charges resulting from all urinary catheter-associated UTIs in 1 month. A cost-analysis of silver-hydrogel urinary catheter use was performed.

RESULTS

The rate of catheter-associated UTIs for noncoated catheters was 4.9/1000 patient-days compared with 2.7/1000 patient-days for the silver-hydrogel catheters, a reduction of 45% (P =.1). The average cost (calculated with hospital charges) of a catheter-associated UTI at our institution was estimated to be $1214.42 US dollars, with a median of $613.72 US dollars. The estimated cost-saving ranged from $12,563.52 US dollars to $142,314.72 US dollars.

CONCLUSIONS

The use of silver-hydrogel urinary catheters resulted in a nonsignificant reduction in catheter-associated UTIs and a modest cost-saving.

Heparin coating reduces encrustation of ureteral stents: a preliminary report

The present study evaluated the inhibition of ureteral stent encrustation by heparin coating. In contrast to uncoated polyurethane stents, heparin coated ureteral stents did not show any organic (biofilms) or anorganic (crystals) deposits after being in situ for up to 6 weeks and effectively inhibited the encrustation process.

Silver. 2: Toxicity in mammals and how its products aid wound repair

The second article examining the role of this metallic element in a wound environment discusses toxicity in individual cells, animals and humans and considers how different silver-based dressings assist in wound healing.

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.

PDMS-based polyurethanes with MPEG grafts: mechanical properties, bacterial repellency, and release behavior of rifampicin

PDMS-based polyurethanes (PUs) grafted with monomethoxy poly(ethylene glycol) (MPEG) were synthesized to develop a coating material for urinary catheters with a silicone surface for minimizing urinary tract infections. MPEG was grafted on PDMS-based PUs by two methods depending on the PU synthetic routes: esterification and allophanate reactions. It was confirmed from mechanical characterization that an increase of the hard segment amount enhanced the ultimate strength and Young's modulus, while reducing elongation at the end-points. The incorporation of MPEG in PDMS-based PUs induced a decrease in tensile strength and Young's modulus, and increased elongation at the break point due to its high flexibility. When hydrated in distilled water, mechanical properties of all PUs synthesized in this study deteriorated due to water absorption. It was evident from the bacterial adhesion test that PDMS-based PUs showed moderate resistance to adhesion of E. coli on their surfaces compared to Pellethane, while the incorporation of MPEG significantly enhanced repellency to bacteria, including E. coli and S. epidermidis. We also studied the release behavior of an antibiotic drug, rifampicin, from the polymeric devices fabricated by solvent evaporation. Although rifampicin is hydrophilic and soluble in pH 7.4 phosphate buffer, it showed a sustained release over 45 days from PDMS-based PUs with MPEG that were grafted on ethylene glycol residues by allophanate reaction. This release characteristic was predominantly influenced by a hydrogen bond interaction between the polymers and rifampicin, which was confirmed through an ATR-IR study. This may imply that the specific interaction is responsible for the delayed release. Considering the mechanical properties, morphologies of drug-incorporated polymeric matrices, and drug release behaviors, PDMS-based PU with MPEG that were grafted on ethylene glycol (a chain extender) residues by allophanate reaction showed better material properties for uretharal catheter coating pusposes in order to minimize urinary tract infections.

Nosocomial Infections in the Intensive Care Unit Associated with Invasive Medical Devices

Modern day health care has become synonymous with cutting-edge, high-tech medicine, which includes a large and growing number of invasive medical devices, especially in intensive care units. The most widely used of these devices--intravascular catheters of many types and urinary catheters--account for more than one half of all institutionally acquired infections. Growing knowledge of the pathogenesis and epidemiology of these infections has given birth to novel and more effective control measures, the most promising of which are technologically based.

Novel strategies to prevent catheter-associated infections in oncology patients

Aggressive cytotoxic treatment of cancer contributes to the growing number of life-threatening infections. Vascular catheters create predominant risks for staphylococcal, enterococcal and candida blood stream infections. Although the contaminating microorganisms may be few in number, the altered host immune response in the presence of such implants as well as disease-associated immunosuppression implies that even small bacterial counts have to be regarded as highly virulent species. Diagnosis of catheter-related infection (CRI) remains difficult before withdrawal of the suspected catheter. Positive culture of catheter surface, lumen and hub and positive peripheral blood probes (paired quantitative blood culture) are predictive for catheter related bacteremia (CRB). Diligent catheter care and effective antimicrobial catheters may reduce prolonged hospital stay, increased morbidity or mortality and serious economical consequences. The most promising approach features the incorporation of antimicrobial drugs into the polymer matrices that entrap but do not bind the drugs, allowing for extended release. For the efficacious prevention of colonization in the microenvironment of the implantable device the concentration of the antimicrobial substances must exceed usual antibiotic concentrations by a thousand-fold. This is the desired effect--high concentration near the device surface and very low systemic concentration. Incorporation of antimicrobials in the bulk material that constitutes a device can be effective as shown in several in vitro and in vivo studies. In the future, modification of both short-term and long-term catheters by biofilm-active antimicrobials creating slow delivery systems may provide an effective method to protect patients from nosocomial infection in oncology.

A European perspective on nosocomial urinary tract infections II. Report on incidence, clinical characteristics and outcome (ESGNI-004 study). European Study Group on Nosocomial Infection

OBJECTIVES

To estimate the incidence of nosocomially acquired urinary tract infections (NAUTI) in Europe and provide information on the clinical characteristics, underlying conditions, etiology, management and outcome of patients.

MATERIALS AND METHODS

We collected clinical information from NAUTI patients with a microbiology report on the named study day.

RESULTS

A total of 141 hospitals from 25 European countries participated in the study. Written institutional bladder catheter guidelines were in place in 90.3% of EU hospitals and 55% of non-EU hospitals (P < 0.05). The total number of new NAUTI episodes on the day of the study was 298, representing an incidence of 3.55 episodes/1000 patient-days and an estimated prevalence of 10.65/1000. The five most commonly isolated micro-organisms were Escherichia coli, Enterococcus sp., Candida sp., Klebsiella sp. and Pseudomonas aeruginosa. Patients from non-EU countries were younger, with more severe underlying diseases with a higher incidence of obstructive uropathy/lithiasis. Overall, 22.8% of patients had no 'classic' UTI-predisposing factors. Catheter-associated UTI (CAUTI) was present in 187 patients (62.8%). A closed drainage system was used in only 78.5% of catheterised patients. The indication for bladder catheterisation was not considered adequate in 7.6% of cases and continuation of bladder catheterisation was considered unnecessary in 31.3%. Opening of the closed drainage system was the most frequent major error in catheter management (16.8%). Antimicrobial treatment was not considered adequate in 19.8% of all cases.

CONCLUSIONS

The incidence of NAUTI in a large European population is 3.55/1000 patient-days. There is clearly room for improvement in the area of bladder catheterisation, catheter care and medical management of NAUTI. We recommend that European authorities draw up and implement practical and specific guidelines to reduce the incidence of this infection.

Infection in the patient with indwelling devices and ostomies

Urinary tract devices, often placed to alleviate obstruction or serve as support for surgical anastamosis, are used with increasing frequency. Although useful, they are fraught with hazards, especially infection. Infected devices have a myriad of clinical presentations that can be unrevealing or even misleading as to the underlying disease process. The astute clinician should maintain a high index of suspicion for such infections. Urinalysis alone has not been adequately studied to demonstrate that it alone can rule out infected foreign material in the urinary tract and should be followed by culture. Failure to recognize and treat infected urological hardware might lead to more rapid progression to ascending infection and more severe illness than expected in the absence of such devices.