Adherence of bacteria to urinary catheters

Summary The adherence of ³H-labelled gram-negative bacilli to different urinary catheter materials was studied using an in vitro method. Adherence was found to be significantly less to siliconised rubber than to pure latex or teflon coated rubber. Adherence was altered by variations in incubation pH, time, and bacterial concentration; however, incubation temperature did not affect results. Adherence of bacteria to urinary tract catheters may be part of the pathogenesis of certain catheter-related infections. However, in the absence of controlled clinical studies the significance of these findings remains to be determined.     

Urinary catheter structure and testing methods in relation to tissue toxicity

Eluates from 56 latex urinary catheters from seven manufacturers were divided into three categories according to covering material (siliconized, silicone elastomer coated and teflon coated) and tested for tissue toxicity by means of cell cultures based on the inhibition of DNA synthesis. The silicone elastomer coated catheters showed the lowest toxicity. Only 4 of 13 such catheters gave unacceptable toxic values, whereas half of the siliconized catheters were abandoned as toxic. Teflon and elastomer coatings had the best protective properties against toxic substances leaching from the catheter core. The surface contour of the catheters estimated by scanning electron microscopy (SEM) did not correlate with toxicity, whereas the cracks seen on the catheters did correlate with toxicity. The simple in vivo test methods used by the manufactures turned out to be insensitive to tissue toxicity testing of urinary catheters. The method used in this study was the most reliable for assessing the safety of latex urinary catheters. Thus manufacturers using multiple and in vitro cell culture tests had products of better quality than those using only a single test or simple in vivo tests.     

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.     

Infection-resistant continuous peritoneal dialysis catheters

The techniques of bonding of anionic antibiotics by treatment with cationic surfactants were applied to continuous ambulatory peritoneal dialysis (CAPD) catheters. The elution of 14C-penicillin from tridodecylmethylammonium chloride (TDMAC) treated silicone elastomer catheters in dialysis solution was biphasic, with 95% dissociated from the catheter by 48 h. Forty percent of the TDMAC left the catheter surface during the initial 2 days. The ability of the surfactant TDMAC to bind antibiotics after incubation in dialysis solution correlated directly with the amount of surfactant remaining. Rats with intraperitoneal dialysis catheters were inoculated with exit site and intraluminal bacterial challenges. Intraperitoneal catheter tips treated with TDMAC-penicillin were rendered more resistant to colonization after exit site and intraluminal bacterial challenges.     

Electrical microcurrent to prevent conditioning film and bacterial adhesion to urological stents

Long-term catheters remain a significant clinical problem in urology due to the high rate of bacterial colonization, infection, and encrustation. Minutes after insertion of a catheter, depositions of host urinary components onto the catheter surface form a conditioning film actively supporting the bacterial adhesion process. We investigated the possibility of reducing or avoiding the buildup of these naturally forming conditioning films and of preventing bacterial adhesion by applying different current densities to platinum electrodes as a possible catheter coating material. In this model we employed a defined environment using artificial urine and Proteus mirabilis. The film formation and desorption was analyzed by highly mass sensitive quartz crystal microbalance and surface sensitive atomic force microscopy. Further, we performed bacterial staining to assess adherence, growth, and survival on the electrodes with different current densities. By applying alternating microcurrent densities on platinum electrodes, we could produce a self regenerative surface which actively removed the conditioning film and significantly reduced bacterial adherence, growth, and survival. The results of this study could easily be adapted to a catheter design for clinical use.     

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.     

Ultrastructural study of microbiologic colonization of urinary catheters

We examined ten urinary catheters, associated with catheter-related urinary tract infections, by scanning and transmission electron microscopy to study the morphology of bacterial adherence. We confirmed that the bacteria associated with catheter-associated urinary tract infections grow in glycocalyx-enclosed microcolonies in a biofilm on the catheter surface. The bacterial populations demonstrated a heterogeneity that was not evident from the culture results, and it was demonstrated that only a small proportion of the microorganisms, including fungi, identified morphologically by scanning or transmission electron microscopy are recovered by routine culture methods. The persistence of the bacterial pathogens in catheter-associated infection, even in the face of antibiotic treatment, may be attributed to their adherent mode of growth in protected biofilms and their production of extensive enveloping anionic glycocalyces.     

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.     

The migration of Proteus mirabilis and other urinary tract pathogens over Foley catheters

OBJECTIVE: To examine the ability of organisms that infect the catheterized urinary tract to migrate over the surfaces of Foley catheters. MATERIALS AND METHODS: In a simple laboratory model, organisms were challenged to migrate across sections of hydrogel-coated latex, hydrogel/silver-coated latex, silicone-coated latex and all-silicone catheters. The sections (1 cm long) were placed as bridges in channels between blocks of agar and the test organisms inoculated onto the agar adjacent to one side of each bridge. The plates were incubated at 37 degrees C for 24 h and examined for growth of the test organisms on the agar on the other side of the bridges. A collection of swarming, swimming and nonmotile species were tested in the model. The relative mobilities of the test organisms were expressed as migration indices, calculated as the percentage of tests in which bacterial migration was observed over each type of catheter bridge. RESULTS: The swarmer cells of Proteus mirabilis and P. vulgaris migrated successfully (migration indices of 73-100) over all four types of catheter. The migration index of Serratia marcescens swarmers was reduced to 33 over the silver-coated catheters, but these cells crossed over the other catheter surfaces with ease (indices of 100). Pseudomonas aeruginosa was the most mobile of the swimming, non-swarming organisms with indices of 70-22, but this group was less capable of migration than the swarmers. Indices were 0-33 for nonmotile organisms. The mean migration indices for the nine species for each type of catheter were 57 (hydrogel-coated latex), 49 (silver/hydrogel-coated latex), 41 (silicone-coated latex) and 35 (all-silicone). The swarmer cells of P. mirabilis moved through populations of Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus and Enterococcus faecalis, and then migrated over sections of hydrogel-coated latex catheters with little or no reduction in migration index. They were also capable of transporting the nonmotile cells of K. pneumoniae and S. aureus over the catheters. The migration index of P. mirabilis swarmers was substantially reduced in the presence of Ps. aeruginosa and S. marcescens. CONCLUSIONS: Hydrogel coatings facilitate the migration of urinary tract pathogens over catheter surfaces. With the exception of S. marcescens, the incorporation of silver into the hydrogel did not inhibit migration. Swarmer cells were particularly effective at moving over catheters and P. mirabilis swarmers were also capable of transporting other species. This suggests that inhibitors of swarming could be useful in controlling catheter-associated infection and the complications resulting from the spread of bacterial biofilm over catheters.     

Nonthrombogenic aortic and vena caval bypass using heparin-coated tubes

In twenty-five acute canine experiments polyvinyl chloride (PVC) tubes, both uncoated and coated with tridodecylmethylammonium chloride/heparin (TDMAC/heparin) complex, were tested in thoracic aortic bypass lasting five hours and in inferior vena caval bypass lasting thirty minutes. In aortic bypass, heparin-coated tubes were almost totally nonthrombogenic in contrast to uncoated tubes which had definite thrombus formation. Smoothly tapered tubes were significantly less thrombogenic than were hybrid tubes with junctions. Tube design, especially junction-free construction, was more important than heparin coating in preventing thrombus formation. In vena caval bypass heparin-coated tubes were totally nonthrombogenic in contrast to uncoated tubes which did show thrombus formation and thrombo-embolism. The smoothly tapered TDMAC/heparin-coated shunt tubes were successfully employed in four patients during thoracic aortic aneurysmal resection.     

Diamond-like carbon coatings on ureteral stents--a new strategy for decreasing the formation of crystalline bacterial biofilms?

PURPOSE: Any catheter material placed in the urinary tract provides a surface for bacterial colonization and, therefore, it is susceptible to encrustation with crystalline bacterial biofilm. Encrustation and blockage by biofilms remain a major complication in patient care. Most patients with indwelling ureteral stents experience irritative symptoms related to these implants and many experience discomfort. MATERIALS AND METHODS: Plasma deposited diamond-like amorphous carbon coatings are well-known for their excellent biocompatibility. A low temperature, low pressure plasma enhanced chemical vapor deposition technology was developed especially for coating polymeric medical implants with diamond-like carbon. We investigated the ability of diamond-like carbon to decrease the formation of crystalline bacterial biofilm as well as stent related side effects and discomfort. Diamond-like carbon coated ureteral Double-J stents were tested in vivo. RESULTS: In 10 patients with heavy encrustation, different underlying diseases and a stent removal frequency of less than 6 weeks due to encrustation a total of 26 diamond-like carbon coated stents were successfully tested for their ability to decrease the extent of crystalline biofilm formation. There was a 2,467-day period of experience with diamond-like carbon coated stents. No primarily stent related complications occurred. No crystalline biofilm formation was observed in vivo. Excellent and facile handling, a less painful replacement procedure and high tolerance of application were reported by physicians and patients. Due to low friction the coated stents could be placed and removed much more easily than standard stents. The frequency and severity of symptomatic urinary tract infections were distinctly decreased. CONCLUSIONS: Diamond-like carbon coating is a new strategy to improve the surface properties of ureteral stents. This novel surface effectively decreases friction, encrustation tendencies and biofilm formation.     

The efficacy of a novel antibacterial hydroxyapatite nanoparticle-coated indwelling urinary catheter in preventing biofilm formation and catheter-associated urinary tract infection in rabbits

The aim of this study was to investigate of the efficacy and reliability of a novel antimicrobial hydroxyapatite (HA) nanoparticle coating of urethral catheters, in the prophylaxis of biofilm formation and bacteriuria in rabbits. A total of 60 male rabbits were randomized to the control and study groups and each group was divided into three subgroups depending on 3, 5 and 7 days of the urethral catheterization period. The rabbits in the study group were catheterized with Ag⁺-incorporated nano-HA coated urethral catheters and those in the control group with standard silicon–latex urethral catheters. Urine and catheter surface smear samples were conducted for bacteriological analysis. Catheter cross-section samples were undergone measuring of biofilm thickness. Tissue samples of bladder and urethra were inspected for histological changes. The results indicate that at the end of 7 days of the catheterization period, the number of the rabbits with bacteriuria was significantly lower in the study group versus control group (p ^¶ = 0.020). The biofilm formation on luminal surface of the catheters was significantly thinner in the study group versus control group, at the end of 5 and 7 days of the catheterization period (0.035 and 0.035, respectively).No histological adverse change or particle penetration was detected in the urothelium. In conclusion, it was observed that Ag⁺ + HA nanoparticle coating significantly lowered the incidence of catheter-related bacteriuria and decreased biofilm formation, at the end of 7 days study period. The novel antimicrobial urethral catheter coating appeared to have a potential in the prophylaxis of catheter-induced urinary tract infections.     

Pentosanpolysulfate coating of silicone reduces encrustation

BACKGROUND AND PURPOSE: A significant problem associated with catheterization in the urinary tract is the encrustation of the catheter materials. One approach to reducing encrustation is to alter the surface properties of the catheters. We evaluated the effectiveness of coating with pentosanpolysulfate (PPS), a semisynthetic polysaccharide similar to heparin, in reducing encrustation and the foreign-body inflammatory response to silicone stents in the bladders of male New Zealand White rabbits. MATERIALS AND METHODS: Sixteen rabbits were divided into three groups to receive placement in their bladders of uncoated (N = 7), PPS-coated (N = 7), or sham matrix-processed silicone rings (N = 2) via open cystotomy. After 50 days of maintenance on normal food and water, all rabbits were sacrificed, and the air-dried, unfixed silicone ring surfaces were examined by scanning electron microscopy. Bladders and remaining silicone rings were removed and preserved separately. Silicone rings, cleaned of all encrustation, were stained with toluidene blue to determine the presence or absence of PPS coating on the surface. RESULTS: Histologic examination revealed normal tissue in bladder sections exposed to coated silicone rings and an inflammatory response in sections from bladders having uncoated silicone rings. Coating with PPS was associated with an eightfold reduction in the amount of encrustation of silicone and a marked reduction in the inflammatory response of the bladder wall to the foreign body. CONCLUSIONS: A PPS coating may be useful in reducing the encrustation of long-term indwelling silicone stents or catheters in the human urinary tract.     

Prevention of catheter sepsis by antibiotic bonding

The techniques of antibiotic bonding were applied to the problem of hyperalimentation catheter sepsis. Pretreatment with tridodecylmethylammonium chloride (TDMAC) increased the bonding of 14C-penicillin to polyethylene catheter segments from 3.1 to 212 micrograms/cm and to silicone elastomer catheter segments from 0.09 to 181 micrograms/cm. The elution of the bound ligands from silicone elastomer catheter segments in the presence of plasma was studied. At 2 weeks more than 60% of the bound TDMAC remained adherent to the catheter. The elution of the bonded penicillin from the silicone elastomer catheters was biphasic, initially 95% dissociated after 48 hours of incubation. A bioassay revealed that the dissociated penicillin was bacteriocidal. Polyethylene catheters were placed in the jugular vein of rats and positioned in the right atrium. The catheters were tunneled posteriorly, exited between the forelimb shoulder girdles, and connected to a swivel mechanism. The exit site was inoculated before closure with 1 X 10(8) Staphylococcus aureus. Five days after insertion the catheters were removed via sterile thoracotomy and the tips cultured. Untreated control catheters, catheters treated by antibiotic soaking, and catheters pretreated with TDMAC all had high rates of catheter colonization (60% to 80)%. TDMAC-penicillin-bonded catheters did not become colonized. This difference was significant (p less than 0.005). Antibiotic bonding may prove effective in preventing hyperalimentation catheter sepsis.     

Heparin prevention of tumor cell adherence and implantation on injured urothelial surfaces

Increasing laboratory and clinical evidence supports the concept of tumor cell implantation as a cause of intravesical recurrence in transitional cell carcinoma of the bladder. The integrity of the surface mucopolysaccharide layer of the bladder has been shown to be crucial in preventing bacterial or crystalline adherence. The purpose of this study was to evaluate the effects of bladder surface mucin integrity on tumor cell adherence and implantation. The adherence of tumor cells to in situ bladders which were either normal, injured, or injured and subsequently heparin-coated was studied using a radiolabeled tumor cell adherence assay. The mechanism of action of heparin in reducing tumor cell adherence and cytotoxic effects of heparin on tumor cells were evaluated. Finally, the ability of topical heparin to reduce tumor implantation rates on injured urothelial surfaces was studied. Urothelial injury by either dilute acid or fulguration resulted in markedly increased tumor cell adherence compared to normal. Topical heparin was capable of reducing cell adherence in injured bladders to control levels. Bladder coating with heparin rather than tumor cell coating was found to be the critical determinant in preventing tumor cell adherence. Heparin had no cytotoxic effects in any of the assays used. The implantation rate in heparin coated bladder was 19% compared to 50% in non-coated bladders. This study suggests that the bladder surface mucopolysaccharide layer plays a critical role in preventing tumor cell adherence and subsequent implantation. Restoration of this layer via exogenous topical heparin is capable of restoring the anti-adherence integrity to the bladder surface.     

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.     

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.     

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).     

In vitro quantitative adherence of bacteria to intravascular catheters

Adapting standard techniques, a simple in vitro system was devised to compare quantitative bacterial adherence to iv catheters of different compositions. Upon brief immersion of catheters in suspensions of Staphylococcus aureus, coagulase-negative staphylococci, and Escherichia coli, organisms adhered to catheter surfaces. After overnight growth in broth, organisms remained adherent and formed colonies, as shown by light and scanning electron microscopy. In addition, quantitative adherence using a blood agar roll technique, expressed as bacteria per square centimeter of catheter surface area per 10(6) colonies per milliliter inoculum, was calculated. Adherence was greater on polyvinylchloride (PVC) catheters (geometric mean 342) than on Teflon catheters (geometric mean 49.6) for coagulase-negative staphylococci (P less than 0.005). Also, the number of coagulase-negative staphylococci adherent to PVC catheters was significantly greater than for E. coli (geometric mean 70.6) at analogous inocula (P less than 0.02). Differences in bacterial adherence to the surface of iv devices may be important in the pathogenesis of catheter-associated infections. This in vitro method could prove useful in testing bacterial adherence properties of newly developed catheter materials, and allow development of catheters less prone to be associated with bacterial adherence and catheter-related infections.     

Plasma-deposited carbon coating on urological indwelling catheters: Preventing formation of encrustations and consecutive complications

BACKGROUND: Any material placed in the urinary tract is susceptible to the formation of encrustations of crystalline bacterial biofilms. These biofilms cause severe complications in some cases. The strategies used so far for reduction of these complications by surface modifications of the implant material failed to show the expected results. PATIENTS AND METHODS: In this study, we investigated amorphous carbon coatings (a-C:H) for their ability to effectively reduce or to repress the progressive formation of infection-enhancing crystalline biofilms as new functional surface coatings. In nine patients suffering for several years from stenting, a-C:H-coated ureteral stents were tested in treatment attempts. The current replacement intervals amounted to a mean of 77 days; the principle cause for early replacement was massive stent encrustations associated with symptomatic urinary tract infections.RESULTS: In total, 20 coated ureteral stents were tested spanning indwelling times between 3 and 4 months. No stent-related complications occurred. In all cases extraordinarily facile handling, less pain during replacement, and markedly increased tolerance were observed. Symptomatic urinary tract infections were reduced by more than 50%. The stents remained virtually free of encrustations. CONCLUSION: a-C:H coatings are a novel strategy leading to an enhancement of long-term applicability of ureteral stents and catheters and to improved patient comfort.