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Biomedical subjects

D J Stickler

Publications and source records attributed to D J Stickler.

At least 19 recordsLinked to original sources
PubMed2006

Observations on the adherence of Proteus mirabilis onto polymer surfaces.

AIMS: Infection of the catheterized urinary tract with Proteus mirabilis causes blockage of the catheter by crystalline bacterial biofilms. The aim of this work is to identify a surface-coating for catheters that is not vulnerable to colonization by Pr. mirabilis. METHODS AND RESULTS: A parallel-plate flow-cell and phase contrast microscopy were used to follow bacterial adhesion onto polymer films. Experiments with a urease-negative mutant of Pr. mirabilis suspended in buffer or urine, identified agarose as a polymer on which biofilm did not form. In tests with wild-type urease-producing cells in urine, no adhesion of cells onto agarose was observed for 3 h but then as the pH rose above 8.2, the surface rapidly became colonized by crystalline biofilm. CONCLUSIONS: In urine at pH below 8.0, Pr. mirabilis does not adhere to agarose-coated surfaces. When the pH rises above 8.2, however, aggregates of crystals and bacteria form in the urine and are deposited on such surfaces. SIGNIFICANCE AND IMPACT OF THE STUDY: Strategies to prevent the formation of crystalline biofilms on urinary catheters will need to consider both the properties of the surface-coatings and the requirement to prevent the alkaline conditions that induce crystal formation in urine.

Bacterial Adhesion↗
PubMed2005

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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Anti-Infective Agents, Local↗
PubMed2005

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.

Anti-Bacterial Agents↗
PubMed2005

Factors modulating the pH at which calcium and magnesium phosphates precipitate from human urine.

The factors controlling the rate at which crystalline bacterial biofilms develop on indwelling bladder catheters are poorly understood. It is known that normally the pH of voided urine (pHv) is lower than the pH at which calcium and magnesium phosphates come out of urine solution (pHn). In patients who develop infections with urease producing bacteria, however, the pHv rises above the pHn and precipitation of the phosphates occurs in the urine and the biofilm. The aim of this study was to examine ways of manipulating the pHn of urine so that more of its calcium and magnesium remain in solution under alkaline conditions. The experimental data show that pHn can be elevated by decreasing the calcium, magnesium and phosphate concentrations. Increasing the fluid intake of a human subject so that the urinary calcium fell from 120 mg/l to 25 mg/l, for example, resulted in the pHn increasing from 6.48 to 8.22. The addition of citrate to urine also produced a rise in the pHn. The daily consumption of 500 ml of fresh orange juice increased urinary citrate concentrations from 0.35 to around 1.21 mg/ml and the pHn rose from 7.24 to 8.2. The pHn of urine is thus a highly variable parameter. It can be manipulated by controlling the urinary concentrations of magnesium, calcium, phosphate and citrate ions. We suggest that increasing fluid intake with citrate containing drinks would reduce the extent of encrustation on catheters in patients infected with urease producing bacteria.

Adult↗
PubMed2005

Does the valve regulated release of urine from the bladder decrease encrustation and blockage of indwelling catheters by crystalline proteus mirabilis biofilms?

PURPOSE: We tested whether valve regulated, intermittent flow of urine from catheterized bladders decreases catheter encrustation. MATERIALS AND METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Biofilms↗
PubMed2005

Role of swarming in the formation of crystalline Proteus mirabilis biofilms on urinary catheters.

The care of many patients undergoing long-term bladder catheterization is frequently complicated by infection with Proteus mirabilis. These organisms colonize the catheter, forming surface biofilm communities, and their urease activity generates alkaline conditions under which crystals of magnesium ammonium phosphate and calcium phosphate are formed and become trapped in the biofilm. As the biofilm develops it obstructs the flow of urine through the catheter, causing either incontinence due to leakage of urine around the catheter or retention of urine in the bladder. The aim of this study was to investigate the role of the surface-associated swarming motility of P. mirabilis in the initiation and development of these crystalline catheter biofilms. A set of stable transposon mutants with a range of swimming and swarming abilities were tested for their ability to colonize silicone surfaces in a parallel-plate flow cell. A laboratory model of the catheterized bladder was then used to examine their ability to form crystalline, catheter-blocking biofilms. The results showed that neither swarming nor swimming motility was required for the attachment of P. mirabilis to silicone. Mutants deficient in swarming and swimming were also capable of forming crystalline biofilms and blocking catheters more rapidly than the wild-type strain.

Bacterial Adhesion↗
PubMed2004

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.

Adult↗
PubMed2003

Control of encrustation and blockage of Foley catheters.

Urinary catheters often become encrusted and blocked by crystalline Proteus mirabilis biofilms. Results of experiments in a laboratory model of a Foley catheterised bladder infected with P mirabilis showed that when retention balloons were inflated with a solution of triclosan (10 g/L), the catheters drained freely for at least 7 days. Triclosan became impregnated throughout the silicone catheter material and completely inhibited the formation of crystalline biofilm, whereas catheters inflated with water became blocked in 24 h. Our observations suggest a way to control a common complication in patients with long-term indwelling bladder catheters.

Biofilms↗
PubMed2003

Molecular epidemiology of Proteus mirabilis infections of the catheterized urinary tract.

Proteus mirabilis compromises the care of many patients undergoing long-term indwelling bladder catheterization. It forms crystalline bacterial biofilms in catheters which block the flow of urine, causing either incontinence due to leakage or painful distention of the bladder due to urinary retention. If it is not dealt with, catheter blockage can lead to pyelonephritis and septicemia. We have examined the epidemiology of catheter-associated P. mirabilis infections by use of pulsed-field gel electrophoresis (PFGE) of NotI restriction enzyme digests of bacterial DNA. This technique was shown to be more discriminatory than the classical phenotypic Dienes typing technique. We demonstrated that each of 42 isolates from diverse environmental sources and 10 of 12 isolates from blood, wound swabs, and mid-stream urine samples of hospitalized patients had distinct genotypes. Examination of a set of 55 isolates of P. mirabilis, each from a different clinical or environmental source, identified 49 distinct genotypes and 43 Dienes types. The index of discrimination was 0.993 for the PFGE method and 0.988 for the Dienes method. Applying the PFGE method to isolates from catheter-associated urinary tract infections confirmed that the strains present in the crystalline catheter biofilms were identical to those isolated from the same patient's urine. An analysis of samples taken during a prospective study of infections in catheterized nursing home patients revealed that a single genotype of P. mirabilis can persist in the urinary tract despite many changes of catheter, periods of noncatheterization, and antibiotic therapy.

Biofilms↗
PubMed2002

Strategies for the control of catheter encrustation.

Two general strategies have been adopted to develop catheter materials that resist encrustaion by bacterial biofilms: (a) the incorporation of antimicrobial agents into the polymers and (b) the production of materials with surface properties which prevent the adherence of bacterial cells. Our experience to develop non-adherent surfaces which abstracts design from nature is reported. Compounds based on 2-methacryloloxyethylphosphorylcholine co-polymerised with long-chain alkyl methacrylates have been produced which have structural and surface properties similar to those of the outer membranes of erythrocytes. These PC-coatings have been applied onto catheter base materials where they produce polar surfaces that are extremely hydrophilic. In experiments using a laboratory model of the catheterised bladder we found that the PC-coatings did not reduce colonisation of latex or silicone catheters by crystalline Proteus mirabilis biofilm. There were no significant difference between the amounts of calcium and magnesium salts deposited on coated and non-coated catheters. In a further set of experiments the PC-coatings did not significantly increase the mean times for which catheters drained freely. In a parallel clinical study, the performance of PC-coated ureteral stents was investigated. Scanning electron microscopy and bacteriological analysis on 44 PC-coated stents that had been implanted in patients for 12-week periods and 28 control stents suggested that the PC-coated devices were less vulnerable to encrustation and colonisation by bacterial biofilm than normal stents. It was of interest that in contrast to encrusted catheters, urease producing species such as P. mirabilis were rarely isolated from the stents. The main organisms colonising the stents were enterococci and coagulase-negative staphylococci. These results suggest that the mechanisms of catheter and stent encrustation may be different and require different strategies for control.

Bacteria↗
PubMed2002

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.

Catheterization↗
PubMed2002

Susceptibility of antibiotic-resistant Gram-negative bacteria to biocides: a perspective from the study of catheter biofilms.

Bacteria resistant to both the agents deployed to prevent infections and those used to treat infections would be formidable nosocomial pathogens. The aim of this paper is to review the evidence that Gram-negative bacteria resistant to antibiotics and biocides have emerged and been responsible for catheter-associated urinary tract infection. A study of patients undergoing intermittent bladder catheterization revealed that the frequent application of the antiseptic chlorhexidine to the perineal skin prior to the insertion of the catheter was effective against the normal Gram-positive skin flora but not against the Gram-negative organisms that subsequently colonized this site. Organisms such as Providencia stuartii, Pseudomonas aeruginosa and Proteus mirabilis were repeatedly isolated from the skin of these patients and inevitably went on to cause urinary infections. The minimum inhibitory concentration (MIC) of chlorhexidine for many of these strains proved to be 200-800 microg ml(-1) compared with the 10-50 microg ml(-1) recorded for reference strains of Gram-negative species. A subsequent survey of over 800 Gram-negative isolates from urinary tract infections in patients from both hospitals and the community revealed that chlorhexidine resistance was not a widespread phenomenon, but was restricted to these species and to units where the care of catheterized patients involved the extensive use of chlorhexidine. Analysis of the antibiotic resistance patterns revealed that the chlorhexidine-resistant strains were also multidrug resistant. Other clinical studies also reported catheter-associated infections with chlorhexidine- and multidrug-resistant strains of Pr. mirabilis when chlorhexidine was being used extensively. This species poses particular problems to the catheterized patient. Chlorhexidine thus proved counterproductive in the care of catheters and its use in this context has been largely abandoned. Suggestions of reintroducing this agent in the form of biocide-impregnated catheters should be resisted.

Anti-Infective Agents, Local↗
PubMed2002

Susceptibility of antibiotic-resistant gram-negative bacteria to biocides: a perspective from the study of catheter biofilms.

Bacteria resistant to both the agents deployed to prevent infections and those used to treat infections would be formidable nosocomial pathogens. The aim of this paper is to review the evidence that gram-negative bacteria resistant to antibiotics and biocides have emerged and been responsible for catheter-associated urinary tract infection. A study of patients undergoing intermittent bladder catheterization revealed that the frequent application of the antiseptic chlorhexidine to the perineal skin prior to the insertion of the catheter was effective against the normal gram-positive skin flora but not against the gram-negative organisms that subsequently colonized this site. Organisms such as Providencia stuartii, Pseudomonas aeruginosa and Proteus mirabilis were repeatedly isolated from the skin of these patients and inevitably went on to cause urinary infections. The minimum inhibitory concentration (MIC) of chlorhexidine for many of these strains proved to be 200-800 microg ml(-1) compared with the 10-50 microg ml(-1) recorded for reference strains of gram-negative species. A subsequent survey of over 800 gram-negative isolates from urinary tract infections in patients from both hospitals and the community revealed that chlorhexidine resistance was not a widespread phenomenon, but was restricted to these species and to units where the care of catheterized patients involved the extensive use of chlorhexidine. Analysis of the antibiotic resistance patterns revealed that the chlorhexidine-resistant strains were also multidrug resistant. Other clinical studies also reported catheter-associated infections with chlorhexidine- and multidrug-resistant strains of Pr. mirabilis when chlorhexidine was being used extensively. This species poses particular problems to the catheterized patient. Chlorhexidine thus proved counterproductive in the care of catheters and its use in this context has been largely abandoned. Suggestions of reintroducing this agent in the form of biocide-impregnated catheters should be resisted.

Animals↗
PubMed2001

Does drinking cranberry juice produce urine inhibitory to the development of crystalline, catheter-blocking Proteus mirabilis biofilms?

OBJECTIVE: To test the recommendation that to avoid the complications of long-term indwelling bladder catheterization (e.g. encrustation and blockage by crystalline Proteus mirabilis biofilms) patients should drink cranberry juice. MATERIALS AND METHODS: Urine was collected from groups of volunteers who had drunk up to 2 x 500 mL of cranberry juice or water within an 8-h period. Laboratory models of the catheterized bladder were supplied with urine from these groups and inoculated with P. mirabilis. After incubation for 24 or 48 h, the extent of catheter encrustation was determined by chemical analysis for calcium and magnesium. Encrustation was also visualized by scanning electron microscopy. RESULTS: The amounts of calcium and magnesium recovered from catheters incubated in urine pooled from individuals who had drunk 500 mL of cranberry juice was not significantly different from that on catheters incubated in pooled urine from control subjects who had drunk 500 mL of water. However, there was significantly less encrustation (P = 0.007) on catheters from models receiving urine from volunteers who had drunk 2 x 500 mL of water than on catheters incubated in models supplied with urine from volunteers who had drunk 2 x 500 mL of cranberry juice. The amounts of encrustation on these two groups of catheters were also significantly less than that on catheters incubated in models supplied with urine from volunteers who had not supplemented their normal fluid intake. (P < 0.001). Experiments in the models using artificial urine showed that increasing the low fluid intake (720 mL/24 h) characteristic of many patients undergoing long-term catheterization by factors of three and six, significantly (P < 0.01) reduced the amounts of calcium and magnesium that formed on catheters. At a simulated fluid intake of 720 mL/24 h, catheters blocked with encrustation after a mean of 42.5 h, while those supplied with urine produced from an intake of 4320 mL/24 h, drained freely for > 10 days. CONCLUSION: In this in vitro study, drinking cranberry juice did not produce urine that was inhibitory to the development of crystalline catheter-blocking P. mirabilis biofilms. The important factor in preventing catheter encrustation is a high fluid intake.

Beverages↗
PubMed1999

The development of bacterial biofilms on indwelling urethral catheters.

The biofilm mode of growth has been implicated in the majority of human bacterial infections. In the urinary tract, notable biofilm-associated infections include prostatitis, chronic cystitis, struvite urolithiasis, and catheter-associated infections. Biofilms protect the causative organisms from host defences and antimicrobial therapy. Biofilm formation has traditionally been considered to result from adhesion and capsule formation by adherent microorganisms. Recent work has shown that a large number of genes are activated during this process, some of which have been associated with twitching motility, quorum sensing, and slow growth. In this paper, we review some of the recent work on biofilm biology and highlight its role in urinary tract infections, particularly those associated with urinary catheters.

Biofilms↗