Catheter Encrustation Research Articles

Use of quorum sensing antagonists to deter the formation of crystalline Proteus mirabilis biofilms

Proteus mirabilis biofilms are a major cause of urinary catheter blockage. Antibiotic-impregnated catheters used to prevent catheter blockage have achieved limited success. Research has examined the efficacy of quorum sensing inhibitors against Pseudomonas aeruginosa biofilms, but there are few reports of the effects of these compounds against crystalline P. mirabilis biofilms. This study examined the effect of two quorum sensing antagonists, p-nitrophenyl glycerol (PNPG) and tannic acid, against crystalline P. mirabilis biofilms. Tannic acid and PNPG were observed to inhibit the quorum sensing system and the formation of P. mirabilis biofilms grown in artificial urine. The success of these compounds provides a possible means of preventing urinary catheter encrustation.

The effect of EDTA instillations on the rate of development of encrustation and biofilms in Foley catheters

The aim of this research was to examine whether a daily instillation of tetra sodium ethylenediaminetetraacetic acid (EDTA) solution could reduce the rate at which encrustation by crystalline Proteus mirabilis biofilms blocks urinary catheters. Sets of three bladder models were fitted with size 14 all-silicone catheters. Tetra sodium EDTA solution was instilled into the catheter following biofilm development. Catheters were examined by digital photography and scanning electron microscopy for evidence of encrustation. The results showed that the mean time to blockage of the control catheters was 45 h for saline, 57 h for water and 67 h for those exposed to daily instillations of the EDTA solution. Statistical analysis confirmed that the mean encrustation rate on the EDTA-treated catheters was significantly lower than on the control-treated devices (P = 0.047). This in vitro study indicates that EDTA may have beneficial effects in reducing the complication of catheter encrustation and blockage by crystalline biofilms.

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.

Reduced Susceptibility of Proteus mirabilis to Triclosan

Clinical isolates of Proteus mirabilis causing catheter encrustation and blockage are susceptible to the biocide triclosan (MICs of 0.2 mg/liter). Studies with laboratory models of the bladder have demonstrated that the inflation of catheter retention balloons with triclosan solutions rather than water results in the diffusion of triclosan from the balloons into the surrounding urine and the inhibition of catheter encrustation by P. mirabilis. The aim of this study was to test whether the exposure of P. mirabilis to triclosan under laboratory conditions resulted in the selection of strains with reduced susceptibilities to this biocide. Exposure to triclosan in agar was shown to select mutants with MICs elevated from 0.2 mg/liter up to 80 mg/liter. In a selection of 14 of these strains, the decreased susceptibility was found to be stable and not associated with increased resistance to antibiotics. Experiments with the laboratory models demonstrated that inflation of the catheter balloons with triclosan (10 mg/ml) prevented encrustation and blockage by the parent strain P. mirabilis B2 (MIC, 0.2 mg/liter) and the mutant strain M48 (MIC, 2.0 mg/liter) but had no effect on crystalline biofilm formation by strain M55 (MIC, 40 mg/liter). These results suggest that, in any clinical trial or subsequent clinical use of the strategy, it will be important to monitor the urinary flora of the catheterized patients for P. mirabilis strains with reduced susceptibility to triclosan. The emergence of these strains could undermine the ability of the triclosan strategy to control catheter encrustation.

Verbessertes Modell der humanen katheterisierten Blase für das Screening antibakteriell wirksamer Agenzien

Catheter encrustation and associated blockage by a crystalline Proteus mirabilis biofilm constitute a continuous problem in long-term catheterised patients. The objective of the present work was to verify a new, physiological bladder model possessing the ability to show that triclosan-blocking solutions exert bactericidal and bacteriostatic activities. Catheterised sterile infusion bags served as human bladder models. Artificial urine inoculated with Proteus mirabilis was administered by a further aperture. Samples for measurement of pH value and microbial count were collected at intervals of 24 h. Upon completion of testing catheter encrustation was assessed and visualised by scanning electron microscopy. In contrast to the application of placebo solution, in models filled with triclosan-blocking solution the catheters drained freely for the experimental period. Similar results were obtained for pH values and microbial count. The pH of the artificial urine did not exceed a critical value of pH 7 and the numbers of organisms correspond approximately to the initially inoculated number of organisms. In the model developed here, triclosan inhibits the growth of Proteus mirabilis over the test period by diffusing into the artificial urine through the catheter balloon. Thus, triclosan acts against the pH increase as well as the formation of a crystalline biofilm. Taken together, the adaptability of this new, physiological model of the human bladder could be shown.

Species interactions in mixed-community crystalline biofilms on urinary catheters

Previous experimental investigations of the crystalline biofilms that colonize and block urinary catheters have focussed on their formation by pure cultures of Proteus mirabilis. In the urine of patients undergoing long-term catheterization, P. mirabilis is commonly found in mixed communities with other urinary tract pathogens. Little is known about the effect that the other species have on the rate at which P. mirabilis encrusts catheters. In the present study, a set of data on the nature of the bacterial communities on 106 catheter biofilms has been analysed and it was found that while species such as Providencia stuartii and Klebsiella pneumoniae were commonly associated with P. mirabilis, when Escherichia coli, Morganella morganii or Enterobacter cloacae were present, P. mirabilis was rarely or never found. The hypothesis that the absence of P. mirabilis from some biofilm communities could be due to its active exclusion by other species has also been examined. Experiments in laboratory models showed that co-infection of P. mirabilis with M. morganii, K. pneumoniae or E. coli had no effect on the ability of P. mirabilis to encrust and block catheters. Co-infection with Ent. cloacae or Pseudomonas aeruginosa, however, significantly increased the time that catheters took to block (P <0.05). The growth of Ent. cloacae, M. morganii, K. pneumoniae or E. coli in the model for 72 h prior to superinfection with P. mirabilis significantly delayed catheter blockage. In the case of Ent. cloacae, for example, the mean time to blockage was extended from 28.7 h to 60.7 h (P < or =0.01). In all cases, however, P. mirabilis was able to generate alkaline urine, colonize the biofilms, induce crystal formation and block the catheters. The results suggest that although there is a degree of antagonism between P. mirabilis and some of the other urinary tract organisms, the effects are temporary and whatever the pre-existing urinary microbiota, infection with P. mirabilis is thus likely to lead to catheter encrustation and blockage.

Developing a strategy to reduce the high morbidity of patients with long-term urinary catheters: the BioMed catheter research clinic

To assess the idea of managing patients having problems with long-term catheterization (LTC, normally used when all other methods of bladder management have failed or are unsuitable) in a dedicated clinic, to present a prospective analysis of consecutive new patients attending between February 2002 and October 2006, and to establish the incidence of bladder stones in patients who have recurrent catheter encrustation and blockage. Patients treated with LTC are a large heterogeneous group, mainly consisting of elderly people who have chronic disabilities, and catheter-associated complications occur in > 70% of them. In all, 260 consecutive new patients having problems with LTC were assessed; the evaluation consisted of basic demographics, a detailed history, clinical examination, urine analysis and flexible cystoscopy (FC) via the catheterization route. Patients with bladder stones were screened with FC for recurrence of stones at 3, 6 and 12 months after treatment. In all, 117 men and 143 women (mean age 67.7 years, range 23-97) were assessed; 147 (55.5%) had catheter encrustation. FC showed that 66 of the 147 patients (45%) had bladder stones. Forty-eight patients (73%) were successfully treated at the same clinic appointment and their stones were removed with the help of a tip-less stone basket. Eighteen patients (27%) were referred for inpatient treatment of bladder stones under general anaesthesia. Twenty of 66 patients with bladder stones (30%) formed recurrent bladder stones at a mean (range) follow-up of 8.1 (3-18 months). In addition, 36 patients had successful insertion of suprapubic catheter (SPC) under local anaesthetic in the clinic, and 11 were referred for SPC insertion under general anaesthesia. Two patients were diagnosed with bladder transitional cell carcinoma. The introduction of a dedicated catheter clinic, equipped with facilities such as FC and a hoist, enables patients to be treated in an environment that meets their needs and potentially reduces the risk of more complex stone removal and catheter problems at a later date. It can also act as a potential source of data for use in research and development. A significant proportion (45%) of patients with catheter encrustation and blockage had formed bladder stones. Our study provides a rationale for FC of all such patients to detect and remove stones.

Some Observations on the Diffusion of Antimicrobial Agents Through the Retention Balloons of Foley Catheters

We examined the ability of antimicrobial agents to diffuse through the retention balloons of urinary catheters and inhibit their encrustation by Proteus mirabilis. 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. 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. 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.

Characterisation of the internal and external surfaces of four types of Foley catheter using SEM and profilometry

Unfortunately the use of Foley catheters for long-term catheterisation is frequently associated with complications such as infection and encrustation. This study investigated whether a link could exist between the surface properties of the catheters and the problems that can develop. The internal and external surfaces of four different types of urinary catheter were examined. Three latex devices coated with either PTFE or hydrogel or surface treated with silicone were investigated. In addition, an all-silicone device was examined. The surfaces of the all-silicone catheters were relatively smooth and featureless. In contrast, the external surfaces of each of the latex devices were 'paved' in nature. The internal surfaces of latex based devices produced by different manufacturers showed distinct differences with evidence of inorganic inclusions on the internal surfaces of two of the catheter types. These findings may be significant in the context of catheter infection and encrustation.

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

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. 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. 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. 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.

A Sensor To Detect the Early Stages in the Development of CrystallineProteus mirabilisBiofilm on Indwelling Bladder Catheters

A simple sensor has been developed to detect the early stages of urinary catheter encrustation and avoid the clinical crises induced by catheter blockage. In laboratory models of colonization by Proteus mirabilis, the sensor signaled encrustation at an average time of 43 h before catheters were blocked with crystalline biofilm.

Factors affecting crystal precipitation from urine in individuals with long-term urinary catheters colonized with urease-positive bacterial species

Weekly urinalysis was conducted for 12 weeks on a group of 21 long-term catheter users with confirmed catheter encrustation and urinary tract colonization with urease-positive bacteria, in order to explore the cause of considerable variation in the severity of encrustation between sufferers. The rapidity of catheter blockage correlated significantly with the pH above which crystals precipitated from urine (the nucleation pH) but not the pH of the voided urine itself. Linear regression showed the nucleation pH to be significantly predicted by a combination of urinary calcium and magnesium concentrations, with calcium being the more influential variable. Reducing the rate of catheter encrustation could be achieved by lowering the urinary concentration of calcium and magnesium, which may only require catheter users to increase their fluid intake.

Accuracy of Predicting Bladder Stones Based on Catheter Encrustation in Individuals With Spinal Cord Injury

Background: Bladder calculi are the second most common urological complication in those with spinal cord injury (SCI). Detection and removal of bladder stones are important to prevent possible complications.Objective: To determine the accuracy of bladder stone detection based on catheter encrustation in asymptomatic individuals with SCI.Design: Prospective cohort study.Methods: Cystoscopy findings in persons with SCI who were noted to have catheter encrustation at the time of catheter removal for their scheduled cystoscopy were used in this prospective study. Indwelling catheters were examined for encrustation at the time of removal as they were being prepared for cystoscopy. Cystoscopy was performed, and the presence or absence of bladder stones was noted.Main Outcome Measures: Presence or absence of bladder stones detected with cystoscopy in those with precystoscopy catheter encrustation.Results: Forty-nine individuals with indwelling catheters were evaluated. Overall, 17/49 (35%) individuals in this study had bladder stones. Catheter encrustation was noted in 13 patients. Of these 1 3 patients, 11 also had bladder stones. In other words, a positive result for catheter encrustation had a positive result for bladder stones 85% of the time. Thirty-six individuals had no catheter encrustation. Of these, 6 (16%) were found to have bladder stones.Conclusions: Encrustation of a catheter is highly predictive of the presence of bladder stones. This suggests that cystoscopy should be scheduled in a person undergoing a catheter change if catheter encrustation is noted.

Effect of triclosan on the development of bacterial biofilms by urinary tract pathogens on urinary catheters

To examine (i) the effect of triclosan on the formation of catheter biofilms by urinary tract pathogens and (ii) the diffusion of triclosan through the retention balloons of urinary catheters. Models of the catheterized bladder were infected with eight different urinary tract pathogens and the effect of triclosan on biofilm formation was assessed by determining the numbers of viable cells colonizing the catheters and by scanning electron microscopy. HPLC was used to determine the triclosan concentration in urine draining from models that had been fitted with triclosan-inflated silicone catheters. When catheters were inflated with triclosan (10 g/L) the formation of catheter biofilm by Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Proteus mirabilis was prevented. The numbers of Enterococcus faecalis and Providencia stuartii cells colonizing catheters were also significantly reduced (P<0.05). Serratia marcescens, Morganella morganii and Pseudomonas aeruginosa, however, were able to produce extensive catheter biofilms in the presence of triclosan. Only P. mirabilis produced alkaline urine and encrusted the catheters. Concentrations of 0.02-0.16 mg/L of the biocide were detected in urine draining from the model over the 48 h experimental period. Triclosan diffused through silicone catheter balloons and produced urinary concentrations that prevented catheter encrustation by P. mirabilis and biofilm formation by several other common pathogens of the catheterized urinary tract. It had little effect on urease-producing P. aeruginosa, S. marcescens or M. morganii but these species did not produce alkaline urine or crystalline biofilms.

Prospective study of individuals with long‐term urinary catheters colonized with Proteus species

To characterize the variability in the times catheters take to block with encrustation in patients who have Proteus in their urinary flora, and to identify factors responsible for modulating the rate of catheter encrustation and blockage. Twenty patients were followed prospectively for > or = 12 weeks, with a bacteriological analysis on weekly urine samples. The pH of the voided urine samples and the pH at which crystals formed in them (the nucleation pH) were determined. Catheters were collected and examined for bacterial biofilm and crystal deposition. The time that catheters took to block was 2-98 days. The mean pH of the urine voided by patients designated as slow encrusters (6.9) was not significantly different (P = 0.237) from that of rapid encrusters (7.2). However, patients whose catheters took longer to block had a significantly higher mean nucleation pH (8.1 vs 7.3, P = 0.002) and significantly higher mean safety margin between their nucleation pH and voided pH (1.17 pH units vs 0.13, P = 0.003). The variation in the rate of catheter encrustation between individuals infected with Proteus is a function of the difference between the voided pH and the nucleation pH of their urine. The value of nucleation pH of an individual's urine varies widely, suggesting it should be possible to devise strategies to increase this value and thus reduce the rate of encrustation in those with urinary tract colonization by urease-positive bacteria.

AN ELECTRIFIED CATHETER TO RESIST ENCRUSTATION BY PROTEUS MIRABILIS BIOFILM

We investigated the effect of iontophoresis produced by passing an electric current through silver electrodes attached to catheters on catheter encrustation by crystalline Proteus mirabilis biofilm. Four glass bladder models were catheterized with 16Fr silicone catheters, of which 3 had 0.25 mm silver wires running through and beside the lumen. Two wired catheters had the silver wires connected to a 9 V direct current source supplying a steady current of 150 microA via a self-regulating circuit. Artificial urine, which had been inoculated with a clinical strain of P. mirabilis isolated from an encrusted catheter, was instilled into the bladder model at 0.5 ml per minute. The models were operated until the test catheters became blocked. Mean blockage time was statistically analyzed by ANOVA. Bacterial colony count, silver ions and pH were assessed every 24 hours. The experiment was repeated 3 times. Time to blockage, colony count, pH and scanning electron microscopy was used to assess encrustation in electrified and control catheters. Time to blockage in electrified vs control catheters was 156 vs 22 hours. The difference in blockage times was statistically significant (p <0.002). The viable bacterial cell count in urine with test catheters vs that in controls was 1.12 x 10(4) vs 2.73 x 10(9) cfu/ml. The pH increased to 9 in control models, whereas it remained less than 6.5 in test models for about 100 hours. Electrified catheters released ions in urine that have the oligodynamic property of inhibiting bacterial growth. The application of electric current to catheters fitted with silver electrodes significantly decreased the rate at which these devices became encrusted by P. mirabilis. This principle could be used to prevent encrustation on long-term catheters.

DOES THE VALVE REGULATED RELEASE OF URINE FROM THE BLADDER DECREASE ENCRUSTATION AND BLOCKAGE OF INDWELLING CATHETERS BY CRYSTALLINE PROTEUS MIRABILIS BIOFILMS?

We tested whether valve regulated, intermittent flow of urine from catheterized bladders decreases catheter encrustation. Laboratory models of the catheterized bladder were infected with Proteus mirabilis. Urine was allowed to drain continuously through the catheters or regulated by valves to drain intermittently at predetermined intervals. The time that catheters required to become blocked was recorded and encrustation was visualized by scanning electron microscopy. When a manual valve was used to drain urine from the bladder at 2-hour intervals 4 times during the day, catheters required significantly longer to become blocked than those on continuous drainage (mean 62.6 vs 35.9 hours, p = 0.039). A similar 1.7-fold increase occurred when urine was drained at 4-hour intervals 3 times daily. Experiments with an automatic valve in which urine was released at 2 or 4-hour intervals through the day and night also showed a significant increase in mean time to blockage compared with continuous drainage (p = 0.001). Scanning electron microscopy confirmed that crystalline biofilm was less extensive on valve regulated catheters. Valve regulated, intermittent flow of urine through catheters increases the time that catheters require to become blocked with crystalline biofilm. The most beneficial effect was recorded when urine was released from the bladder at 4-hour intervals throughout the day and night by an automatic valve.

Genotyping Demonstrates That the Strains of Proteus Mirabilis From Bladder Stones and Catheter Encrustations of Patients Undergoing Long-Term Bladder Catheterization are Identical

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. 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. 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. 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.

PH testing in catheter maintenance: the clinical debate.

The pH of urine is widely recognized as being a major contributory factor in urinary catheter encrustation. What is less widely appreciated is the range of factors that affect the pH of urine, and which therefore affect the reliability and validity of urine pH testing. This article examines the validity of various urinary pH testing methods and discusses the theoretical and practical implications of the uncertainty surrounding their practical value.

Managing recurrent urinary catheter encrustation.

Recurrent blockage of the urinary catheter is a common problem in around 40-50% of long-term catheterized patients, leading to problems which are distressing to patients and costly to health services in both time and resources. Blockage is frequently caused by the build-up of mineral deposits on the catheter surface following precipitation from the urine under alkaline conditions. The presence of urea-splitting bacteria in the urine promotes a strongly alkaline urine and their adhesion to the catheter as a biofilm makes them extremely difficult to remove. This article addresses strategies for early identification of potential 'blockers'; proactive approaches to care; and the evidence for use of catheter maintenance solutions.