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

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.

Catheter-associated urinary tract infections

Nosocomial urinary tract infection (UTI) is the most common infection acquired in both hospitals and nursing homes and is usually associated with catheterization. This infection would be even more common but for the use of the closed catheter system. Most modifications have not improved on the closed catheter itself. Even with meticulous care, this system will not prevent bacteriuria. After bacteriuria develops, the ability to limit its complications is minimal. Once a catheter is put in place, the clinician must keep two concepts in mind: keep the catheter system closed in order to postpone the onset of bacteriuria, and remove the catheter as soon as possible. If the catheter can be removed before bacteriuria develops, postponement becomes prevention.

Catheter-associated urinary tract infections: impact of catheter materials on their management

Infection associated with an indwelling catheter is a representative type of biofilm infection occurring in the urinary tract. Since the most effective way to control this intractable infection is the prevention of bacterial attachment and subsequent biofilm formation on the catheter, the importance of catheter materials and anti-bacterial coating cannot be underestimated. The difference in the degree of bacterial attachment among standard catheter materials, the efficacy of silver-coating of catheters in preventing infection and the potency and effectiveness of a new lecithin/silver coating are discussed.

Prophylactic efficacy of a new gentamicin-releasing urethral catheter in short-term catheterized rabbits

OBJECTIVE

To describe an indwelling urethral catheter coated with gentamicin sulphate on the inner and outer surface of the catheter, and to evaluate the efficacy and safety of this catheter in preventing catheter-associated infections in rabbits. Materials and methods Sixty rabbits were divided equally into control and experimental groups which were then subdivided equally according to the duration of catheterization (1, 3 and 5 days). Silicone-treated latex catheters were used in the control group and gentamicin-releasing catheters in the experimental group. Urine samples and surface swabs from the catheter were cultured for bacteriological assessment, and the catheter surface examined by scanning electron microscopy to structurally analyse the biofilms.

RESULTS

The gentamicin-releasing catheter reduced the incidence of bacteriuria (defined as > or = 100 c.f.u./mL) after both 3 and 5 days of catheterization (eight and 10 rabbits, respectively, for the control catheter, vs two and four rabbits for the gentamicin-releasing catheter, P < 0.05). The surfaces of the gentamicin-releasing catheter were colonized less often than those of the control catheter after both 3 and 5 days (eight and 10, respectively, for the control, vs one and four for the gentamicin-releasing catheter, P < 0.05). Scanning electron microscopy showed the formation of bacterial biofilm throughout the 3-day and 5-day control catheters, but deterioration of the bacterial biofilm was visible on the surface of the gentamicin-releasing catheters.

CONCLUSION

This new gentamicin-releasing catheter produced an antibacterial barrier which inhibited catheter-associated urinary tract infection with no toxicity for at least 5 days. These in vivo studies suggest that this new catheter may be useful for controlling infection, with systemic and local safety, in patients undergoing short-term indwelling urethral catheterization.

Engineering out the risk for infection with urinary catheters

Catheter-associated urinary tract infection (CAUTI) is the most common nosocomial infection. Each year, more than 1 million patients in U.S. acute-care hospitals and extended-care facilities acquire such an infection; the risk with short-term catheterization is 5% per day. CAUTI is the second most common cause of nosocomial bloodstream infection, and studies suggest that patients with CAUTI have an increased institutional death rate, unrelated to the development of urosepsis. Novel urinary catheters impregnated with nitrofurazone or minocycline and rifampin or coated with a silver alloy-hydrogel exhibit antiinfective surface activity that significantly reduces the risk of CAUTI for short-term catheterizations not exceeding 2-3 weeks.

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.

Effect of the adhesive antibiotic TA on adhesion and initial growth of E. coli on silicone rubber

Catheter-associated urinary tract infection is the most common nosocomial infection, and contributes to patient morbidity and mortality. We investigated the effect that the TA adhesive antibiotic had on adhesion and initial growth in urine of Escherichia coli on silicone rubber. The TA antibiotic had reduced adhesion, and inhibited initial growth of the bacteria on the surface. Since adhesion and initial growth on the surface are an essential part of biofilm formation and subsequent infection, we speculate that the TA antibiotic coating might decrease the infection rate associated with indwelling urinary catheter.

Randomized multi-centre trial of the effects of a catheter coated with hydrogel and silver salts on the incidence of hospital-acquired urinary tract infections

Catheters coated with hydrogel and silver salts have been proposed to prevent hospital-acquired urinary tract infections (UTI). We carried out a randomized, prospective, double-blind multi-centre trial to compare those catheters with classical urinary tract catheters. We included in the study 199 patients requiring urethral catheterization for more than three days: 109 in group 1 (classical catheter) and 90 in group 2 (catheter coated with hydrogel and silver salts). Urine from the patients was tested for 10 days after the insertion of the catheter (reactive dipsticks each day and diagnostic urinalysis every two days). The UTI associated with catheterization was defined on the basis of bacterial and cytological criteria (>10(5)cfu bacteria per mL and >10 leucocytes per mm(3)). Twenty-two UTIs were recorded: 13 in group 1 and nine in group 2. The cumulative incidence of UTI associated with catheterization was 11.1% overall, 11.9% for group 1 and 10% for group 2; the odds ratio was 0.82 (95% confidence interval: 0.30 to 2. 20); the cumulative incidence for UTI, calculated by the Kaplan-Meier method was 36.3 overall, 35.2 in group 1 and 36.0 in group 2; the overall incidence density was 19 per thousand days of catheterization, 21 in group 1 and 18 in group 2. The differences between the two groups were not significant. Overall, we feel that there is not enough evidence to conclude that catheters coated with silver salts and hydrogel give greater protection than classical catheters and to recommend widespread use.

Clinical and economic consequences of nosocomial catheter-related bacteriuria

Indwelling catheters are strongly associated with the development of bacteriuria, which can lead to significant morbidity in hospitalized patients. This report, a review of the literature, evaluates the infectious outcomes of patients with indwelling catheters to determine the precise clinical and economic impact of catheter-related infection. Statistical pooling was used to estimate the incidence of bacteriuria in hospitalized patients with indwelling catheters. In addition, the proportion of patients with catheter-related bacteriuria in whom symptomatic urinary tract infection and bacteremia will develop was estimated through quantitative synthesis of previous reports. Costs were estimated by using microcosting techniques. Of patients who have indwelling catheters for 2 to 10 days, bacteriuria is expected to develop in 26% (95% confidence interval [CI], 23% to 29%). Among patients with bacteriuria symptoms of urinary tract infection will develop in 24%, (95% CI, 16% to 32%), and bacteremia from a urinary tract source will develop in 3.6% (95% CI, 3.4% to 3.8%). Each episode of symptomatic urinary tract infection is expected to cost an additional $676, and catheter-related bacteremia is likely to cost at least $2836. Given the clinical and economic burden of urinary catheter-related infection, infection control professionals and hospital epidemiologists should use the latest infection control principles and technology to reduce this common complication.

A short history of the Foley catheter: from handmade instrument to infection-prevention device

Although it is one of the most frequently utilized devices in the hospitalized patient, the Foley catheter has often been taken for granted. This lack of attention is unfortunate, as the Foley catheter remains one of the primary sources of hospital-acquired infections, which increase morbidity, mortality, and the financial burden on the healthcare system. Although education on the appropriate techniques, proper use, and early removal of Foley catheters is important, such measures unfortunately result in transient benefits. Current technologic advancements have moved the coating technology to a state where bacterial adhesion and migration can be limited and the frequency of catheter-associated urinary tract infections can be reduced. Future technological advances in the Foley catheter will help provide better care and comfort for the catheterized patient.

Infection-resistant alloplasts

Prosthesis-related infection accounts for nearly half of nosocomial infections, resulting in significant morbidity, mortality, prolonged hospitalization, and higher healthcare costs. Although numerous antimicrobial-coated surfaces have been suggested to guard against prosthesis-related infection, only a few, such as minocylcine plus rifampin, are clinically protective. The differences in clinical efficacy can be attributed at least in part to differences in the magnitude of leaching of the antimicrobial agent off the surface. There is a pressing need to explore the clinical efficacy of antimicrobial surfaces suitable for use in devices intended for long-term use.

Activities of a nitrofurazone-containing urinary catheter and a silver hydrogel catheter against multidrug-resistant bacteria characteristic of catheter-associated urinary tract infection

The in vitro inhibitory activity of a nitrofurazone-coated urinary catheter (NFC) against 86 recently obtained susceptible and multidrug-resistant (MDR) clinical isolates of Escherichia coli, Klebsiella pneumoniae, Citrobacter freundii, Staphylococcus aureus, coagulase-negative staphylococci, and Enterococcus faecium, which are species implicated in catheter-associated urinary tract infection and which traditionally have been susceptible to nitrofuran derivatives, was determined using an agar diffusion assay. In a subset of these strains, the activity of the NFC was compared with that of a silver hydrogel urinary catheter (SHC), and the durability of each catheter's inhibitory activity was assessed during serial daily transfers of catheter segments to fresh culture plates. Except for vancomycin-resistant E. faecium, the NFC was active against all isolates tested and showed comparable inhibition zones with susceptible and MDR strains of each species. In contrast, the SHC inhibited only certain staphylococci (P < 0.01 versus the NFC), and among these strains, the SHC produced smaller inhibition zones than did the NFC (P < 0.01). Inhibition was evident for up to 5 days with the NFC, but for only 1 day (if at all) with the SHC (P < 0.01). These data document that, for most genera which traditionally have been susceptible to nitrofuran derivatives, the NFC remains active against contemporary MDR isolates. They also demonstrate that the in vitro antibacterial activity of the NFC is markedly superior to that of the SHC in several respects. Thus, the NFC shows promise for clinical use in the current era of MDR bacteria.

Antibiotic hydrogel coated Foley catheters for prevention of urinary tract infection in a rabbit model

PURPOSE

We developed an antibiotic liposome (ciprofloxacin liposome) containing hydrogel for external coating of silicone Foley catheters and evaluated its efficacy in a rabbit model. Our goal was to create a catheter that would hinder the development of catheter associated nosocomial urinary tract infections.

MATERIALS AND METHODS

We inserted either an untreated, liposomal hydrogel coated or a liposome hydrogel with ciprofloxacin coated 10F silicone Foley catheter into New Zealand White rabbits. We challenged the system with 5x10(6) virulent Escherichia coli at the urethral meatus twice daily for 3 days. Urine cultures were evaluated twice daily for 7 days. When urine cultures became positive, the rabbits were sacrificed and urine, urethral catheter and urethral tissue were cultured.

RESULTS

The time to bacteriuria detection in 50% of the specimens was double for hydrogel with ciprofloxacin coated catheters versus untreated and hydrogel coated catheters. A significant (p = 0.04) improvement in average time to positive urine culture from 3.5 to 5.3 days and a 30% decrease in the bacteriuria rate for hydrogel with ciprofloxacin coated catheters were noted compared to untreated catheters.

CONCLUSIONS

A significant benefit was realized by coating the extraluminal catheter surface with a ciprofloxacin liposome impregnated hydrogel. We believe this procedure will provide a significant clinical advantage, while reducing health care costs substantially.

Catheter-associated infections in urology: possible use of silver-impregnated catheters and the Erlanger silver catheter

Indwelling urinary catheters play a very important part in urology. However, their use is accompanied by a considerable increase in the risk of nosocomial urinary tract infections. The pathophysiological cause is ascribed to pathogens that adhere to the catheter surface, proliferate and produce a biofilm. In addition to aseptic techniques, modification of the catheter material to confer antimicrobial activity plays an essential part in the prevention of catheter-related urinary tract infections. The antimicrobial efficacy of silver against gram-positive and gram-negative bacteria is well known and amply shown in vitro. The efficacy of silver-impregnated catheters is critically dependent on both the chemical structure of the incorporated silver and the way the silver has been combined with the basic catheter material. Hence, clinical studies on silver-modified catheters have so far given inconsistent results. The new technology of the Erlanger silver catheter offers the opportunity of an effective reduction in catheter-related infections.

Efficacy of silver-coating central venous catheters in reducing bacterial colonization

OBJECTIVE

To compare silver-coated and uncoated central venous catheters regarding bacterial colonization. To assess the relative contribution of catheter hub and skin colonization to catheter tip colonization.

DESIGN

Prospective, randomized clinical trial.

SETTING

Intensive care unit in a university hospital.

PATIENTS

Patients after cardiac surgery who required a central venous double-lumen catheter (DLC).

INTERVENTIONS

Sixty-seven adult patients were prospectively randomized to receive either a silver-coated (S group, n = 34) or an uncoated control (C group, n = 33) DLC. Blood cultures were drawn at catheter removal, and removed catheters were analyzed with quantitative cultures. Typing of microorganisms included DNA fingerprinting.

MEASUREMENTS AND MAIN RESULTS

Catheters were removed if no longer necessary and aseptically divided into three segments: segment A, the catheter tip; segment B, an intermediate section; and segment C, the subcutaneous portion. Bacterial catheter colonization was quantitatively measured using sonication to detach adherent bacteria from the catheter segments in the broth and subsequent culture of an aliquot. Selected isolates of coagulase-negative staphylococci and other bacteria from catheter segments were examined by means of pulsed-field gel electrophoresis (PFGE) after macrorestriction digestion of bacterial DNA to study colonization pathogenesis. Quantitatively lower bacterial colonization could be demonstrated on the silver-coated catheters (200 +/- 550 colony forming units [CFUs]/cm catheter segment; mean +/- SD). The difference in the control catheters (1120 +/- 5350 CFUs/cm catheter segment; mean +/- SD) was not, however, significant (p = .25). The frequency of colonization of at least one catheter segment was 52.9% for the silver-coated catheters and 57.6% for the control catheters (p= .44), without any significant differences in the colonization of corresponding catheter segments. The rate of significant catheter colonization (i.e., > or = 10(3) CFUs/cm catheter by quantitative catheter culture or > or = 10(3) CFUs/mL by luminal flush) was nine in the silver group and seven in the control group, a difference that failed to reach significance (p = .41). Two patients in both groups developed catheter-related bacteremia. Pattern analysis after PFGE demonstrated that about 70% of the isolates found on the catheter tip were identical with those on the skin at the insertion site, whereas about 75% were identical with those recovered from the hub. In 29% of colonized catheters, identical bacteria were found on the hub and the skin at the insertion site.

CONCLUSIONS

Silver-coating of DLCs did not significantly reduce bacterial catheter colonization compared with the control catheters. PFGE analysis of coagulase-negative staphylococci and other bacteria demonstrated various pathogenic routes of catheter-related colonization, whereby the microorganisms of the skin flora around the insertion site must be regarded as the main source of catheter-related infections.

A prospective study of pathogenesis of catheter-associated urinary tract infections

OBJECTIVE

To determine the pathogenesis of catheter-associated urinary tract infection (CAUTI) and the relative importance of each of the possible mechanisms of entry of infecting microorganisms to the catheterized urinary tract.

MATERIAL AND METHODS

We conducted a prospective study of 1,497 newly catheterized patients. Paired quantitative urine cultures were obtained daily, from the catheter specimen port and from the collection bag, using a technique that could detect 1 colony-forming unit/mL. We assumed that with extraluminal infections, caused by microorganisms ascending from the perineum in the mucous film contiguous to the external surface of the catheter, the organisms would be detected first in bladder urine or in far higher concentrations in urine from the specimen port than from the collection bag. With intraluminal CAUTIs, caused by microorganisms gaining access to the catheter lumen because of failure of closed drainage or contamination of collection bag urine, the organisms would be detected first or in far larger numbers in a collection bag specimen.

RESULTS

The probable mechanism of infection could be determined for 173 of 250 organisms (69.2 %) identified in 235 new-onset CAUTIs. Among these 173 cases, 115 (66%) were extraluminally acquired, and 58 (34%) were derived from intraluminal contaminants. For these determinable cases, CAUTIs caused by gram-positive cocci (enterococci and staphylococci) and yeasts were far more likely to be extraluminally acquired (extraluminal:intraluminal, 2.9) than were gram-negative bacilli, which caused CAUTIs by both routes equally (extraluminal: intraluminal, 1.2; P = 0.007). Surprisingly, no significant differences were noted in pathogenetic mechanisms between men and women.

CONCLUSION

We conclude that, in both men and women, CAUTIs occur by both extraluminal and intraluminal portals of entry but derive preponderantly from organisms that gain access extraluminally. Strategies for prevention of CAUTIs must focus on new technologies to prevent access of organisms by all possible routes.

The efficacy of silver alloy-coated urinary catheters in preventing urinary tract infection: a meta-analysis

PURPOSE

Indwelling urinary catheters are implicated in most cases of nosocomial urinary tract infection. Silver-coating of catheters may reduce the risk of these infections; however, trials have provided mixed results. We performed a meta-analysis to estimate the effectiveness of silver-coated urinary catheters.

SUBJECTS AND METHODS

Published or unpublished articles were sought using MEDLINE, reference review, and correspondence with original authors, catheter manufacturers, and experts. Trials using silver-coated urinary catheters in the treatment group and uncoated urinary catheters in the control group were included. Bacteriuria, as evaluated by urine culture, was the outcome variable used to indicate urinary tract infection. Summary odds ratios (OR) and 95% confidence intervals (CI) were calculated using Mantel-Haenszel methods with a fixed-effects model.

RESULTS

Of 117 reports retrieved, eight trials with a total of 2,355 patients satisfied inclusion criteria. The summary OR for urinary tract infection was 0.59 (95% CI, 0.42 to 0.84) indicating a significant benefit in the patients receiving silver-coated catheters. A test of heterogeneity, however, indicated that the odds ratios varied significantly among studies. Silver alloy catheters (OR = 0.24; 95% CI, 0.11 to 0.52) were significantly more protective against bacteriuria than silver oxide catheters (OR = 0.79; 95% CI, 0.56 to 1.10).

CONCLUSIONS

This meta-analysis clarifies discrepant results among trials of silver-coated urinary catheters by revealing that silver alloy catheters are significantly more effective in preventing urinary tract infections than are silver oxide catheters. Though silver alloy urinary catheters cost about $6 more than standard urinary catheters, they may be worth the extra cost since catheter-related infection is a common cause of nosocomial infection and bacteremia.

Activity of silver ions in different media

A major problem in medicine is the large number of infections associated with implanted and indwelling devices. Silver coating of medical devices is believed to preserve infection resistance. Several in vitro and animal studies as well as clinical observations on silver-nylon, silver-intramedullary pins, silver-oxide-Foley catheters and silver-coated vascular protheses have been interpreted as successful for the prophylaxis of foreign-body infections. Nevertheless, these products have not been established in clinical use. In this study we have been able to present physico-chemical and pharmacological data as well as simple microbiological experiments explaining the reduced anti-microbial activity of silver-ions in some biological fluids.

Adhesion of bacteria to stainless steel and silver-coated orthopedic external fixation pins

Bacterial adhesion to silver-coated orthopedic external fixation pins was compared with stainless steel controls in an in vitro study. Using five bacterial isolates from wound infections, the silver coating was found to reduce adhesion for Escherichia coli, Pseudomonas aeruginosa, and two strains of Staphylococcus aureus while the converse applied for Staphylococcus haemolyticus. When placed in human serum, both surfaces were conditioned to a similar extent with serum proteins; this conditioning lead to further reductions in bacterial adhesion, ultimately approaching similar levels for both stainless steel and silver-coated samples.

Catheter-associated urinary tract infections

Millions of urethral catheters are used each year. This device subverts several host defenses to allow bacterial entry at the rate of 3% to 10% incidence per day, and its presence encourages the organism's persistent residence in the urinary tract. Most catheter-associated bacteriurias are asymptomatic. The complications in short-term catheterized patients include fever, acute pyelonephritis, bacteremia, and death; patients with long-term catheters in place are at risk for these complications and catheter obstruction, urinary tract stones, local periurinary infections, chronic renal inflammation, chronic pyelonephritis, and, over years, bladder cancer. The closed catheter system has been a magnificant step forward in the prevention of catheter-associated bacteriuria. Indeed, only two catheter principles are universally recommended: keep the closed catheter system closed and remove the catheter as soon as possible. Most modifications of the closed catheter system have not improved markedly on its ability to postpone bacteriuria. On first inspection, systemic antibiotics seem to be an exception to this rule, but their use results in infection of the bladder with resistant organisms, including candida. This and the effect of side effects on the patient and emergence of resistant bacteria in the medical unit have led most authorities to conclude that antibiotics are not useful for prevention of bacteriuria, nor for treatment of bacteriuria in the asymptomatic catheterized patient. For symptomatic patients, usually with fever or signs of sepsis, treatment of bacteriuria with appropriate systemic antibiotics and removal or replacement of the urethral catheter are indicated. Gloves, hand washing, and segregation of catheterized patients can minimize nosocomial clusters. Because clinicians can only postpone bacteriuria, and once it occurs, clinicians seem unable to prevent its complications, methodologies other than urethral catheters should be used for urine drainage assistance whenever possible. These options include condom, intermittent, suprapubic, and intraurethral catheterization for appropriate patients. The few data available suggest that each one of these catheterization options yields a lower incidence of bacteriuria-and its consequent complications-than urethral catheterization.