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.     

Some observations on the diffusion of antimicrobial agents through the retention balloons of foley catheters

PURPOSE: We examined the ability of antimicrobial agents to diffuse through the retention balloons of urinary catheters and inhibit their encrustation by Proteus mirabilis. MATERIALS AND METHODS: An agar diffusion screening test was developed to detect agents capable of diffusing through catheter balloons and inhibiting the growth of P. mirabilis. The effect of inflating the balloons with antibacterials on the ability of P. mirabilis to encrust catheters was tested in laboratory models of the catheterized bladder. RESULTS: Of 18 antimicrobial agents active on P. mirabilis only mandelic acid, phenoxyethanol, nalidixic acid and triclosan diffused through all-silicone catheter balloons to produce zones of inhibition against P. mirabilis. Polyurethane balloons were permeable to gentamicin and fluoroquinolones. Experiments with silicone catheters showed that inflating balloons with mandelic acid (100 gm/l) or ciprofloxacin (10 gm/l) failed to extended the time at which catheters became blocked in models inoculated with P. mirabilis. However, nalidixic acid (50 gm/l) significantly extended the lifespan of catheters (p <0.05). Triclosan (10 gm/l) prevented the increase in urinary pH that induces crystal formation and inhibited the formation of crystalline biofilm, enabling the catheters to drain freely for the full 7-day experimental period. CONCLUSIONS: Inflation of silicone catheter retention balloons with solutions of nalidixic acid or triclosan rather than water should be considered as strategies to control catheter encrustation. Polyurethane balloons are more permeable than silicone balloons to gentamicin and the fluoroquinolones, and they should be investigated as an alternative to silicone or latex in catheter manufacture.     

Biocompatibility of urinary catheters. Effect on complement activation

The ability of 2 brands of urinary catheters to activate the complement system in vitro as a marker of biocompatibility was investigated. Pieces of a silicone/latex catheter and an all-silicone catheter were incubated in human serum. Complement activation was tested in 2 enzyme immunoassays, one evaluating C3 activation and the other the terminal complement complex (TCC) formation. The silicone/latex catheter caused considerably more complement activation in both assays than did the all-silicone one. The findings are in agreement with previous results of tissue toxicity tests. The methods presented may prove valuable for the practical purpose of testing the biocompatibility of urinary catheters.     

A strategy for the control of catheter blockage by crystalline Proteus mirabilis biofilm using the antibacterial agent triclosan

OBJECTIVES: Catheter blockage by crystalline Proteus mirabilis biofilm is a common complication in patients undergoing long-term indwelling bladder catheterisation. Previously we have shown that inflating the retention balloons of all-silicone catheters with triclosan solutions prevents the encrustation process. The aim of the present work was to examine whether this strategy is effective in latex-based catheters. METHODS: Laboratory bladder models were fitted with catheters and the retention balloons inflated with water or various concentrations of triclosan. The urine was inoculated with Pr. mirabilis and the times catheters took to block recorded. RESULTS: Control catheters blocked in mean times ranging from 18 to 27 h. The pH of the urine rose from 6.1 to >8.6. In models with latex-based catheters inflated with 1-10 mg/ml triclosan, the urinary pH was controlled, the numbers of organisms in the urine was reduced and the catheters drained freely for the 7 day experimental period. Electron microscopy confirmed that crystalline biofilm was blocking control catheters. Little sign of encrustation was visible on the test catheters. CONCLUSION: Inflating the retention balloons with triclosan could have practical applications in controlling encrustation on both latex and silicone-based catheters.     

Toxicity study of first and second generation hydrogel-coated latex urinary catheters

The hydrogel-coated urinary catheter is a novel formulation in which the coating hydrogel polymer is claimed to reduce the level of cytotoxicity frequently associated with the use of latex catheters. This study was undertaken to measure cytotoxicity using in vivo techniques. Twelve first generation and 5 second generation hydrogel-coated latex catheters were evaluated in vivo using canine urethras. The results showed all catheters to cause minimal inflammatory changes of the urethral mucosa (toxicity score 0-1.2/6).     

Swarming of Proteus mirabilis over ureteral stents: a comparative assessment

BACKGROUND AND PURPOSE: Encrustation on indwelling ureteral stents is commonly related to the presence of urease-producing bacteria that elevate the pH of the urine through the hydrolysis of urea, resulting in the precipitation of calcium and magnesium salts. Using a model previously shown to measure accurately the ability of Proteus mirabilis to swarm over catheter surfaces (Eur J Clin Microbiol Infect Dis 1999;18:206), we investigated the ability of this organism to swarm over three ureteral stents with potential encrustation-resistance properties. MATERIALS AND METHODS: Three commercially available ureteral stents were selected for evaluation: a low surface-energy stent, a hydrogel-coated stent, and a silicone stent. Ten-microliter aliquots of a 4-hour culture of P. mirabilis 296 in Trypticase soya (TSA) broth was inoculated 5 mm from a 1-cm channel cut out from TSA plates. Ten-millimeter stent sections were placed as bridges across the central channel adjacent to the inocula. Time to pathogen crossing was measured. RESULTS: The mean time (+/- SD) to pathogen migration across the three test materials was 15.9 +/- 6.1, 19.8 +/- 9.5, and 29.7 +/- 14.3 hours for the low surface-energy, hydrogel-coated, and silicone stents, respectively. Statistical analysis revealed significant differences between the crossing times of the low surface-energy (P = 0.001) and hydrogel-coated (P = 0.034) stents compared with silicone but not between the low surface-energy and hydrogel-coated stents (P = 0.387). CONCLUSION: Migration of P. mirabilis 296 across silicone stents was significantly reduced compared with low surface-energy and hydrogel-coated stents. These findings suggest that P. mirabilis may have a lower affinity for silicone stents, which may translate into a reduced risk of infection with P. mirabilis and associated stent encrustation.     

Comparison of urethral reaction to full silicone, hydrogen-coated and siliconised latex catheters

Indwelling urinary catheter may induce an inflammatory reaction or even stricture of the urethra. Catheter encrustation and urinary infection are other disadvantages associated with long-term catheterisation. In the present study, 77 male patients were catheterised randomly as part of their normal treatment with 1 of 3 different types of catheter: 22 siliconised latex, 28 hydrogel-coated latex and 27 full silicone catheters. The mean duration of catheterisation was 2.2 days. The urethral inflammatory reaction was assessed from cytological urethral swab specimens. Catheter encrustation was studied using scanning electron microscopic (SEM) analysis. The full silicone catheters induced the mildest degree of inflammation in the urethra, the percentage mean of inflammatory cells in smears being 20%. In both latex catheter groups the value was 36%. Neither the age of the patients nor the duration of catheterisation had any effect on the inflammatory reaction, which was more marked in patients with haemodynamic abnormalities. The hydrogel coating effectively prevented encrustation, while siliconised latex catheters were the least resistant to encrustation. The inflammatory reaction was variable in all patients. The use of urethral catheters should be restricted and suprapubic tubes should be used instead, particularly in patients with shock-like circulatory changes. By developing the biocompatibility and physical properties of urinary catheters, more compatible devices may be manufactured.     

Formation of encrustations on indwelling urinary catheters in the elderly: a comparison of different types of catheter materials in "blockers" and "nonblockers"

In order to determine the effect of catheter materials on formation of encrustations in long-term indwelling urinary catheters in the elderly we performed a crossover study utilizing commercially available silicone, silicone-coated, teflon-coated and latex catheters that were left in place for 14 days. The study was conducted with #18 french catheters fitted with a 30 ml. balloon since smaller size catheters frequently fell out spontaneously. The distinction between patients who were "blockers" and "nonblockers" was found to be clinically useful since "nonblockers", who constituted about half the population, did well regardless of type of catheter material used. Formation of encrustations and blockage was significantly less in "blockers" with silicone than with teflon-coated or latex catheters. The more rapid flow-time through silicone catheters appears to be related to a larger bore. Although this study supports the use of silicone catheters for "blockers" on long-term drainage the results should not be interpreted to imply that they are preferable to other types of catheters for short-term use or to changing less expensive catheters more frequently when needed.     

A study of the structure of the crystalline bacterial biofilms that can encrust and block silver Foley catheters

The aim of this study was to examine the structure of the crystalline bacterial biofilms that encrust and block silver/hydrogel-coated latex catheters. Scanning electron microscopy was used to examine the crystalline deposits that were found encrusting catheters obtained from six patients undergoing long-term catheterization in a community setting. Large populations of bacilli and cocci were seen on all catheters developing on a basal foundation layer of crystalline material. These observations show that in patients prone to catheter encrustation, crystalline material formed in the urine can cover the surfaces of silver catheters. Extensive bacterial biofilms then develop on the crystals, shielded from the underlying silver. It is suggested that if antimicrobials are to be incorporated into catheters to prevent encrustation, they must diffuse out from the catheter surface and reduce the viable cell populations of the urease producing bacteria that elevate the urinary pH and trigger crystal formation.     

Catheter-associated urinary tract infections

In the past few years it has been clearly demonstrated that the concept of bacterial biofilm production permits an understanding and provides some explanation of the pathogenesis, diagnosis and treatment of catheter-associated urinary tract infections. This concept describes the colonization of catheter surfaces and the movement of bacteria against the urinary flow. It explains the antibacterial resistance of these matrix-enclosed sessile populations of bacteria. The catheter encrustation can be observed as mineralizing bacterial biofilm. The differentiation in swarming cells exposing a much higher activity of the enzyme urease is responsible for the predominant role of Proteus mirabilis in obstructing encrustations. The guidelines for the prevention of catheter-associated urinary tract infections were developed over the past decades by clinicians and are still valid. They can now be better understood taking into consideration these new theories. As overuse of urethral catheters and non-compliance of their recommended use are still apparent, educational and surveillance programmes are needed to help maintain good standards of care.     

A clinical assessment of the performance of a sensor to detect crystalline biofilm formation on indwelling bladder catheters

OBJECTIVES: To test the ability of a sensor developed to signal infection by the organisms that generate the crystalline biofilms that encrust catheters, to give an early warning that encrustation was occurring on patients' catheters, as the care of many patients undergoing long-term bladder catheterization is complicated by the encrustation and blockage of their catheters. PATIENTS AND METHODS: Twenty patients were followed prospectively for the lifetime of one of their catheters. Sensors based on cellulose acetate/bromothymol blue were placed in the urine-collection bags, which were changed as usual at weekly intervals. The bacteriology was assessed and pH determined weekly on urine samples. Photographic records were made of the sensors twice weekly. On removal, each catheter was examined for encrustation and blockage. RESULTS: Proteus mirabilis was not isolated from five patients and in these cases the sensor colour remained golden-yellow to brown. The catheters drained for the scheduled period and showed no signs of encrustation. By contrast, the sensors turned dark blue/black in the urine of all 15 patients infected with P. mirabilis. All these patients' catheters were encrusted and in 12 the catheters blocked. The mean interval between the sensor signalling and the catheter blocking was 12 days. CONCLUSION: The cellulose acetate/bromothymol blue sensors placed in the urine collection bags are capable of signalling infection by P. mirabilis. They also signal the early stages of catheter encrustation and allow catheter replacement in ample time to avoid the clinical crises and emergency referrals caused by catheter blockage.     

Refinements in the coating of urethral catheters reduces the incidence of catheter-associated bacteriuria. An experimental and clinical study

The tendency to develop bacteriuria during the use of various forms of indwelling catheters was evaluated in a randomized trial in 90 patients. A silver alloy and hydrogel-coated Foley catheter (SHC) was compared to a non-coated catheter (NC) and a catheter coated only with hydrogel (HC). Three patients (10%) with SHC catheters, 10 (33%) patients with HC catheters, and 15 (50%) patients with NC catheters developed bacteriuria (greater than 10(5) organisms/ml). The difference in the rate of bacteriuria after 5 days of catheterization was statistically significant between the SHC catheter and the NC catheter (p less than 0.002). There was no significant difference between the SHC catheter and the HC catheter, nor was there a significant difference between the HC catheter and the NC catheter. The toxic effects, as estimated by the IC50 value, of the urinary catheter material used was elucidated in an experimental fibroblast model. The IC50 value for the NC catheter was 33.9%, HC catheter 72.2% and for the SHC catheter 98.1%.     

Clinical application of the Bardex IC Foley catheter.

OBJECTIVES: We performed two randomized prospective studies with the silver-coated Bardex IC catheter in order to evaluate the incidence of bacteriuria during short- and medium-term catheterization after urological procedures. METHODS: During catheterization only consecutive suprapubic urine samples were taken and cultured. After removal of the catheter the patient was allowed one wash-out void, and before the second micturition a suprapubic puncture was performed to collect a culture specimen. RESULTS: In the first trial, after radical prostatectomy 18 patients with the Bardex IC catheter were compared to 17 patients with a silicon catheter after the same procedure. There was no significant difference in bacteriuria after 14 days (50.0 vs. 53.3%). In the second part of the study 180 patients were evaluated 101 with latex and 79 with Bardex IC catheters. The median catheterization time was 5 days. The results show a significant delay in the onset of bacteriuria when a silver alloy catheter is used (p < 0.003). On day 5 only 6.3% had bacteriuria in the Bardex IC group versus 11.9% in the latex group. CONCLUSION: We conclude that, after urological procedures, short-term catheterization with the Bardex IC catheter is superior to the classical latex catheter.     

Genotyping demonstrates that the strains of Proteus mirabilis from bladder stones and catheter encrustations of patients undergoing long-term bladder catheterization are identical

PURPOSE: We established the incidence of bladder stones in patients who experienced recurrent encrustation and blockage of indwelling bladder catheters and examined the relationship between isolates of Proteus mirabilis from the stones and from the crystalline biofilms on the catheters. MATERIALS AND METHODS: The first 100 patients attending a clinic for patients experiencing problems with the management of long-term bladder catheters were studied. Flexible cystoscopy was used to detect bladder stones. Catheter encrustation was assessed visually and by electron microscopy. Bacteriological analysis was performed on the stones and catheter biofilms. P. mirabilis isolates were genotyped by pulsed field gel electrophoresis of restriction enzyme digests of bacterial DNA. RESULTS: Most patients (85%) had been referred because of catheter blockage and in 61 (72%) the catheters were encrusted. P. mirabilis was recovered from 37 of 47 encrusted catheters (79%) that were examined but not from any nonencrusted catheters. Of the 61 patients with encrusted catheters 38 (62%) had bladder stones. Pairs of isolates of P. mirabilis from the stones and the catheter biofilms from 6 patients were genotyped. The DNA profiles of each pair of isolates were identical. CONCLUSIONS: The majority of patients (62%) with recurrent catheter encrustation had bladder stones. The stones harbored the strains of P. mirabilis that rapidly colonize replacement catheters with crystalline biofilm. Flexible cystoscopy to detect and remove stones might help resolve the problem of recurrent catheter encrustation.     

Hydrogel/silver ion-coated urinary catheter reduces nosocomial urinary tract infection rates in intensive care unit patients: a multicenter study

Objectives. Indwelling urinary catheters are the leading source of nosocomial urinary tract infections (NUTIs). The Bardex I.C. catheter is a hydrogel latex Foley catheter with a monolayer of silver metal applied to the inner and outer surfaces of the catheter. We investigated the Bardex I.C. catheter for its ability to decrease the NUTI rate in critical care units.Methods. Five hospitals participated in a blind prospective study, exchanging the standard latex Foley catheter for the Bardex I.C. Foley catheter. The device use rate and NUTI rate were monitored. Data were collected and analyzed using Wilcoxon rank sum test and four-way analysis of variance. A cost analysis was also performed.Results. The baseline period, intervention period, and number of device days was similar for both periods. The unadjusted catheter-associated infection rate during the baseline and intervention periods was 7.1 and 4.5 infections per 1000 catheter days, respectively (P <0.01). The adjusted catheter-associated infection rate during the baseline and intervention periods was 8.1 and 4.9 infections per 1000 catheter days, respectively. This was not statistically significant (P = 0.13).Conclusions. A trend toward a reduction in NUTIs with the use of the hydrogel/silver-coated catheter was noted in all intensive care units at each institution as shown by the unadjusted and adjusted catheter-associated infection rates. One hospital demonstrated a statistically significant reduction in NUTIs. However, statistical significance was not met when the results were adjusted. The cost analysis at one institution demonstrated cost savings with the use of the silver-coated catheter. Future analysis may require a double-blind, prospective-controlled study of longer duration to reach statistical significance.     

Silver alloy coated catheters reduce catheter-associated bacteriuria

The tendency of indwelling catheters to cause urinary tract infection was evaluated in a randomised clinical study of 223 patients. A Foley catheter coated with silver alloy on both inner and outer surfaces was used in 60 patients; 60 others received a Teflonised latex Foley's catheter and the remaining 103 patients were excluded because of antibiotic treatment, diabetes, etc. There was a statistically significant difference in the incidence of catheter-associated bacteriuria (greater than 10(5) organisms/ml) in the 2 groups after 6 days' catheterisation: 6 patients with the silver coated catheter developed bacteriuria compared with 22 who had the Teflonised latex catheter. This suggests that the silver impregnated urethral catheters reduce the incidence of catheter-associated urinary tract infection.     

Comparison of in vitro encrustation on silicone and hydrogel-coated latex catheters

Mid-shaft sections of 100% silicone (Bardex) and hydrogel-coated latex (Biocath) catheters were subjected to controlled in vitro encrustation conditions for periods of up to 18 weeks. There was no significant difference in the quantities of encrusting deposits formed on these two materials during the course of the experiment.     

Cytotoxicity of latex urinary catheters

After an epidemic of severe urethral strictures in cardiac surgery patients, all brand latex catheters marketed in Finland were investigated for cellular toxicity with eluates made from the catheters. Four of the seven brands, including the one involved in the stricture cases, showed marked cytotoxicity and inhibited almost all cell growth in various human cell cultures when a 30% catheter eluate was used. DNA histograms of cells cultured with toxic catheter eluate showed inhibition of DNA synthesis. Silicone catheters did not influence cell growth, which correlates with the finding that no new stricture cases were seen after the latex catheters were replaced with silicone ones. Attention is paid to the facts that international standards regarding urethral catheter toxicity are lacking and that catheter quality control is insufficient.     

Effect of catheter material on the incidence of urethral strictures.

The aetiology of urethral strictures in patients catheterised for short periods at the time of surgery is the subject of some debate. The occurrence of epidemics of strictures associated with certain batches of latex catheters, and the demonstrable in vitro cytotoxicity of latex in general, have supported the suggestion that catheter material (and in particular latex) has an important role. We have looked retrospectively at 299 patients undergoing transurethral resection of the prostate gland by 1 urologist, 135 of whom had a latex catheter and 164 a plastic one; 19 patients developed strictures over the next 12 months with no proven difference attributable to the catheter material. The study provides no evidence that the short-term use of latex catheters is associated with stricture formation.     

Self-sterilizing catheters with titanium dioxide photocatalyst thin films for clean intermittent catheterization: Basis and study of clinical use

OBJECTIVE: Clean intermittent catheterization (CIC) requires a large number of disposable catheters or a large amount of water and disinfectant. We made titanium dioxide (TiO(2))-coated catheters for CIC using technology we have developed previously, and examined the photocatalytic antibacterial effect of this catheter using only light energy and the safety of this type of catheter for practical clinical use. METHODS: TiO(2)-coated catheters were filled with bacterial cell suspensions and illuminated with a 15-W black-light lamp for testing antibacterial potency. Next, we soaked control toxic materials (zinc diethyldithiocarbamate) and the tips of TiO(2)-coated catheters in M05 medium, and evaluated cell toxicity from the numbers of V79 colonies in these dilutions. Then, bodyweight curves and histological tissue changes were observed over a period of time in mouse-transplanted TiO(2)-coated catheters and control catheters. Finally, we investigated the use of these TiO(2)-coated catheters in 18 patients by questionnaire and bacterial culture of TiO(2)-coated catheters and control catheters. RESULTS: The survival rate of Escherichia coli in the liquid inside the TiO(2) catheter decreased to a negligible level within 60 min under ultraviolet (UV)-A illumination. The survival rate of Staphylococcus aureus, Pseudomonas aeruginosa and Serratia marcescens also decreased to a negligible level within 60 min. V79 cells showed no cytotoxicity of this catheter, and there was no difference in bodyweight or foreign body reaction between mouse-transplanted TiO(2)-coated catheters and control catheters. In a preliminary clinical analysis of 18 patients who voluntarily used this catheter, the rate of positive bacterial culture of the tips of TiO(2)-coated catheters was 20% versus 60% for conventional catheters after 4 weeks of use. CONCLUSION: TiO(2)-coated silicone catheters were easily sterilized under certain light sources and were shown to be safe in an experiment using cultured cells and in animal experiments. Sterilizing catheters with TiO(2) photocatalyst thin films are expected to be used clinically for clean intermittent catheterization after proper modification based on this study.