Some observations on urinary tract infections in patients undergoing long-term bladder catheterization

Evaluating Efficacy of Antimicrobial and Antifouling Materials for Urinary Tract Medical Devices: Challenges and Recommendations

In Europe, the mean incidence of urinary tract infections in intensive care units is 1.1 per 1000 patient-days. Of these cases, catheter-associated urinary tract infections (CAUTI) account for 98%. In total, CAUTI in hospitals is estimated to give additional health-care costs of £1-2.5 billion in the United Kingdom alone. This is in sharp contrast to the low cost of urinary catheters and emphasizes the need for innovative products that reduce the incidence rate of CAUTI. Ureteral stents and other urinary-tract devices suffer similar problems. Antimicrobial strategies are being developed, however, the evaluation of their efficacy is very challenging. This review aims to provide considerations and recommendations covering all relevant aspects of antimicrobial material testing, including surface characterization, biocompatibility, cytotoxicity, in vitro and in vivo tests, microbial strain selection, and hydrodynamic conditions, all in the perspective of complying to the complex pathology of device-associated urinary tract infection. The recommendations should be on the basis of standard assays to be developed which would enable comparisons of results obtained in different research labs both in industry and in academia, as well as provide industry and academia with tools to assess the antimicrobial properties for urinary tract devices in a reliable way.

Bacteriophage-mediated control of a two-species biofilm formed by microorganisms causing catheter-associated urinary tract infections in an in vitro urinary catheter model

Microorganisms from a patient or their environment may colonize indwelling urinary catheters, forming biofilm communities on catheter surfaces and increasing patient morbidity and mortality. This study investigated the effect of pretreating hydrogel-coated silicone catheters with mixtures of Pseudomonas aeruginosa and Proteus mirabilis bacteriophages on the development of single- and two-species biofilms in a multiday continuous-flow in vitro model using artificial urine. Novel phages were purified from sewage, characterized, and screened for their abilities to reduce biofilm development by clinical isolates of their respective hosts. Our screening data showed that artificial urine medium (AUM) is a valid substitute for human urine for the purpose of evaluating uropathogen biofilm control by these bacteriophages. Defined phage cocktails targeting P. aeruginosa and P. mirabilis were designed based on the biofilm inhibition screens. Hydrogel-coated catheters were pretreated with one or both cocktails and challenged with approximately 1×10(3) CFU/ml of the corresponding pathogen(s). The biofilm growth on the catheter surfaces in AUM was monitored over 72 to 96 h. Phage pretreatment reduced P. aeruginosa biofilm counts by 4 log10 CFU/cm2 (P≤0.01) and P. mirabilis biofilm counts by >2 log10 CFU/cm2 (P≤0.01) over 48 h. The presence of P. mirabilis was always associated with an increase in lumen pH from 7.5 to 9.5 and with eventual blockage of the reactor lines. The results of this study suggest that pretreatment of a hydrogel urinary catheter with a phage cocktail can significantly reduce mixed-species biofilm formation by clinically relevant bacteria.

Clinical complications of urinary catheters caused by crystalline biofilms: something needs to be done

This review is largely based on a previous paper published in the journal Spinal Cord. The care of many patients undergoing long-term bladder catheterization is complicated by encrustation and blockage of their Foley catheters. This problem stems from infection by urease-producing bacteria, particularly Proteus mirabilis. These organisms colonize the catheter forming an extensive biofilm; they also generate ammonia from urea, thus elevating the pH of urine. As the pH rises, crystals of calcium and magnesium phosphates precipitate in the urine and in the catheter biofilm. The continued development of this crystalline biofilm blocks the flow of urine through the catheter. Urine then either leaks along the outside of the catheter and the patient becomes incontinent or is retained causing painful distension of the bladder and reflux of urine to the kidneys. The process of crystal deposition can also initiate stone formation. Most patients suffering from recurrent catheter encrustation develop bladder stones. P. mirabilis establishes stable residence in these stones and is extremely difficult to eliminate from the catheterized urinary tract by antibiotic therapy. If blocked catheters are not identified and changed, serious symptomatic episodes of pyelonephritis, septicaemia and endotoxic shock can result. All types of Foley catheters including silver- or nitrofurazone-coated devices are vulnerable to this problem. In this review, the ways in which biofilm formation on Foley catheters is initiated by P. mirabilis will be described. The implications of understanding these mechanisms for the development of an encrustation-resistant catheter will be discussed. Finally, the way forward for the prevention and control of this problem will be considered.

An indwelling urinary catheter for the 21st century

What's known on the subject? and What does the study add? A vast literature has been published on the prevalence, morbidity and microbiology of catheter-associated urinary tract infections. Research and development in recent years has focused on producing antibacterial coatings for the indwelling Foley catheter with insufficient attention to its design. This article provides a critical examination of the design of the indwelling Foley catheter. Design specifications are outlined for a urine collection device that should reduce the vulnerability of catheterised urinary tract to infection. The indwelling urinary catheter is the most common cause of infections in hospitals and other healthcare facilities [1]. As long ago as 1958, Paul Beeson [2] warned '… the decision to use this instrument should be made with the knowledge that it involves the risk of producing a serious disease which is often difficult to treat'. Since then, scientific studies have progressed revealing a greater understanding of the bladder's defence mechanisms against infection and how they are undermined by the Foley catheter [3-5]. In addition, the complications caused by the development of bacterial biofilms on catheters have been recognised and the ways in which these bacterial communities develop on catheters have become clear [5,6]. It is now obvious that fundamental problems with the basic design of the catheter, which has changed little since it was introduced into urological practice by Dr Fredricc Foley in 1937 [7], induce susceptibility to infection. These issues need to be addressed urgently if we are to produce a device suitable for use in the 21st century.

The encrustation and blockage of long-term indwelling bladder catheters: a way forward in prevention and control

OBJECTIVES

To review the literature showing that understanding how Foley catheters become encrusted and blocked by crystalline bacterial biofilms has led to strategies for the control of this complication in the care of patients undergoing long-term indwelling bladder catheterization.

METHODS

A comprehensive PubMed search of the literature published between 1980 and December 2009 was made for relevant articles using the Medical Subject Heading terms 'biofilms', 'urinary catheterization', 'catheter-associated urinary tract infection' and 'urolithiasis'. Papers on catheter-associated urinary tract infections and bacterial biofilms collected during 40 years of working in the field were also reviewed.

RESULTS

There is strong experimental and epidemiological evidence that infection by Proteus mirabilis is the main cause of the crystalline biofilms that encrust and block Foley catheters. The ability of P. mirabilis to generate alkaline urine and to colonize all available types of indwelling catheters allows it to take up stable residence in the catheterized tract in bladder stones and cause recurrent catheter blockage.

CONCLUSION

The elimination of P. mirabilis by antibiotic therapy as soon as it appears in the catheterized urinary tract could improve the quality of life for many patients and reduce the current expenditure of resources when managing the complications of catheter encrustation and blockage. For patients who are already chronic blockers and stone formers, antibiotic treatment is unlikely to be effective owing to the resistance of cells in the crystalline biofilms. Strategies such as increasing fluid intake with citrated drinks could control the problem until bladder stone removal can be organized.

Bacterial biofilms in patients with indwelling urinary catheters

Bacteria have a basic survival strategy: to colonize surfaces and grow as biofilm communities embedded in a gel-like polysaccharide matrix. The catheterized urinary tract provides ideal conditions for the development of enormous biofilm populations. Many bacterial species colonize indwelling catheters as biofilms, inducing complications in patients' care. The most troublesome complications are the crystalline biofilms that can occlude the catheter lumen and trigger episodes of pyelonephritis and septicemia. The crystalline biofilms result from infection by urease-producing bacteria, particularly Proteus mirabilis. Urease raises the urinary pH and drives the formation of calcium phosphate and magnesium phosphate crystals in the biofilm. All types of catheter are vulnerable to encrustation by these biofilms, and clinical prevention strategies are clearly needed, as bacteria growing in the biofilm mode are resistant to antibiotics. Evidence indicates that treatment of symptomatic, catheter-associated urinary tract infection is more effective if biofilm-laden catheters are changed before antibiotic treatment is initiated. Infection with P. mirabilis exposes the many faults of currently available catheters, and plenty of scope exists for improvement in both their design and production; manufacturers should take up the challenge to improve patient outcomes.

Effect of triclosan on the formation of crystalline biofilms by mixed communities of urinary tract pathogens on urinary catheters

The crystalline bacterial biofilms that encrust Foley catheters compromise the care of many elderly and disabled patients. The aim of this study was to examine whether the biocide triclosan can prevent encrustation by the mixed flora of uropathogens that commonly infect patients undergoing long-term catheterization. Models of the catheterized bladder were inoculated with communities of organisms isolated from patients who were experiencing catheter blockage. The catheter retention balloons were inflated with water or triclosan (3 g triclosan l−1 in 0.1 M sodium carbonate) and urine was supplied to the models for up to 7 days. The effect of triclosan was recorded on the viable cell populations, the pH of the residual urine and the times that catheters took to block. The extent of encrustation of the catheters was visualized by scanning electron microscopy. In models inoculated with communities containing Proteus mirabilis, triclosan prevented the rise in urinary pH that drives crystalline biofilm formation and catheter blockage. The biocide had no effect on populations of Enterococcus faecalis and Pseudomonas aeruginosa, but Proteus mirabilis, Escherichia coli and Klebsiella pneumoniae were eliminated from the residual urine and the catheters drained freely for the 7-day experimental period. In models inoculated with a mixed community containing Providencia rettgeri, catheters inflated with triclosan continued to block rapidly. Although K. pneumoniae and Proteus vulgaris were eliminated from the residual urine, there was no effect on the viability of Providencia rettgeri. The results indicate that the triclosan strategy should be limited to the treatment of patients who are infected with Proteus mirabilis.

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.

Biofilms on indwelling urethral catheters produce quorum-sensing signal molecules in situ and in vitro

Acylated homoserine lactones (AHLs) are chemical signals that mediate population density-dependent (quorum-sensing) gene expression in numerous gram-negative bacteria. In this study, gram-negative bacilli isolated from catheters were screened for AHL production by a cross-feeding assay utilizing an AHL-responsive Agrobacterium tumefaciens reporter strain. Positive reactions were obtained from 14 isolates of Pseudomonas aeruginosa; negative or weakly positive reactions were recorded for isolates of five other species. P. aeruginosa biofilms were then produced on catheters in a physical model of the bladder. Sections of colonized all-silicone catheters gave positive reactions for the quorum-sensing signal molecules as did sections that had been cleaned of biofilm and autoclaved. Control sections of unused catheters were negative in the tests. Sections from four of nine catheters that had been freshly removed from patients gave positive reactions for AHLs. Cleaned autoclaved sections of three of these catheters also gave strongly positive reactions for AHLs. These results demonstrate that AHLs are produced by biofilms as they develop on the catheters both in vitro in the model and in vivo in the patient's bladder. They represent the first demonstration of AHL production by biofilms in a clinical setting.

The management of urinary catheters: compliance of practice in Danish hospitals, nursing homes and home care to national guidelines

The compliance of practice to national guidelines on urethral catheter care has been examined. Questionnaires on the practices used with patients under their care were sent to 1350 nursing staff. Replies were received from 1153 individuals, 692 from hospitals, 345 from nursing homes and 116 from home care. While national guidelines stress the importance of maintaining a closed urine drainage system, the results revealed that 25.4% of respondents opened the drainage system to collect samples of urine for analysis, 57.9% to perform bladder washouts and 76% to change urine bags. 26% of respondents reported that they collected urine samples for routine bacteriological surveillance, a procedure considered unnecessary in the guidelines. 83% of staff reported that they washed their hands after emptying urine bags. Staff awareness of written guidelines for various aspects of catheter care ranged from 25-68% in hospitals, 27-45% in nursing homes and 7-17% in home care. A marginal costs analysis was performed to estimate the economic consequences of non-compliance to the national guidelines.

Complications of urinary tract infections associated with devices used for long-term bladder management

The long-term indwelling urethral catheter continues to be a major cause of morbidity in patients in hospitals, nursing homes and home care. Many authorities have recommended that wherever possible, alternative techniques should be considered for the management of patients with urinary retention or incontinence. This article considers the complications that develop from the urinary tract infections associated with long-term indwelling catheterization and reviews the evidence that the other options for bladder management pose less serious threats to health.

Colonization of urinary catheters by Escherichia coli and Providencia stuartii in a laboratory model system

A laboratory model system was developed to investigate the progressive colonization of urinary catheters by Escherichia coli Providencia stuartii, prominent organisms in the polymicrobial bacteriuria of the long-term catheterized urinary tract. We hypothesized that colonization of the catheter and artificial urine by E. coli is influenced by the presence of P. stuartii. E. coli or P. stuartii in pure culture both rapidly colonized the artificial urine and catheters, and both persisted throughout all experiments. In systems containing both organisms, P. stuartii occurred in significantly higher numbers in the artificial urine and on the catheters than E. coli (p < 0.05). To obtain similar numbers of E. coli and P. stuartii in the artificial urine, citrate was eliminated; however, P. stuartii still dominated on the catheter surfaces. The presence of P. stuartii appeared to facilitate growth of E. coli in the artificial urine, yet reduce numbers of E. coli on the catheter. In a separate experiment using different strains of E. coli and P. stuartii, the latter was dominant in the artificial urine and on the catheter surfaces. However, this strain of P. stuartii (which was urease positive) did not facilitate growth of E. coli. The interaction between these strains may have been considerably affected by urea hydrolysis, which resulted in an increase in pH (6.5 to > 8.5) and considerable precipitate formation in the model system. The paradox of P. stuartii enhancing colonization by E. coli in the artificial urine, yet inhibiting its colonization on the catheter surface, illustrates the complexity of polymicrobial interactions in colonization of the catheterized urinary tract.

Blockage of urethral catheters by bacterial biofilms

We report the case of a 63-year-old woman whose indwelling urethral catheter became blocked regularly at 4-5 day intervals over a period of 10 weeks. 'Worm-like' structures 25-30 cm in length were found either in the catheter, completely occluding the lumen, or in the drainage tube thereby blocking the valve of the drainage bag. Electron microscopy showed that these structures were composed of bacteria, while culture revealed them to be mixed communities of Pseudomonas aeruginosa, Escherichia coli, Enterococcus faecalis and Proteus mirabilis. Following treatment with ciprofloxacin, catheter drainage continued freely for a further period of 10 weeks.

Audit of catheter management provided by District Nurses and Continence Advisors

District Nurses and Continence Advisors were surveyed by post to audit their management of long-term indwelling catheters. They were asked to outline, anonymously, their management strategies in response to common specified catheter-related problems. The responses to each question were graded for the appropriateness of strategy from A (best) to E (worst) by previously formulated criteria. Completed questionnaires were returned from all 10 Welsh Continence Advisors and 73 of 139 (53%) District Nurses in South Glamorgan regularly involved in catheter care. A greater proportion of Continence Advisors' than District Nurses' responses were graded A or B in all problem areas specified. In patients with marked bacteriuria, 60% of Continence Advisors but only 11% of District Nurses would assess whether the patient was ill; 53% of District Nurses would treat with antibiotics without such assessment. Whereas most nurses investigating suprapubic pain would consider catheter blockage, only one-third would consider further history taking or examination, and only 1 District Nurse considered constipation or detrusor spasm. Although two-thirds of nurses sometimes used bladder washouts, few considered them effective and most were aware of the potential risks. Thus wide variations were found in the community nursing management of indwelling catheters and care may frequently be suboptimal. Appropriate management guidelines should be developed and disseminated.

Virulence factors in Escherichia coli from urinary tract infections in patients with spinal injuries

A collection of 70 strains of Escherichia coli from urinary tract infections in spine-injured patients undergoing long-term bladder catheterization were tested for characteristics that have been associated with the ability to produce pyelonephritis. The incidence of the virulence factors were: mannose-resistant haemagglutinins (30%), P-fimbriae (17%), haemolysin (27%), K-antigens (28%) and aerobactin (by bioassay 33%, by gene probe 39%). Only 54% of the strains belonged to the O-serotypes usually associated with urinary tract infections. E. coli carrying the full complement of virulence factors were rare in the urinary tract of the spinal patients and were not associated with episodes of symptomatic pyelonephritis. It is clear that the neuropathic bladder and the presence of the catheter permits a wide variety of bacterial types to colonize the urinary tract and cause infection of the kidney. The identification of host markers rather than bacterial factors is suggested as a more fruitful approach to the early detection of cases likely to progress to pyelonephritis in this group of patients.

N-nitrosamine generation by urinary tract infections in spine injured patients

Urine was collected from 33 patients resident at the Welsh Spinal Injuries Unit and analysed for volatile N-nitrosamines by gas chromatography. N-nitrosodime-thylamine, N-nitrosopiperidine or N-nitrosopyrrolidine was detected in 32 of the samples. Thirty-one of the samples were infected by one or more microbial species. Nitrate and N-nitrosamines were not found in the sterile urines of a group of 10 control individuals exposed to the same dietary and environmental influences as the spinal patients. Although N-nitrosamines were found in some of the catheter drainage system products, they did not elute into urine on 24-h exposure. In addition, 6 of the nitrosamine-containing urines had no contact with drainage systems as they were collected from spinal patients who were capable of independent voiding. It was concluded that the nitrosamines detected in the urines arose from the bacterial nitrosation of urinary amines. These results support the hypothesis that chronic urinary tract infection may have a role in the aetiology of bladder cancer in spine injured patients.

The effect of repeated instillations of antiseptics on catheter-associated urinary tract infections: a study in a physical model of the catheterized bladder

The activity of three antiseptic bladder washout solutions was examined in a physical model of the catheterized bladder. Tests were performed against cultures of four common urinary tract pathogens that had established themselves in the model and colonized the surfaces with biofilm. Double instillations of chlorhexidine (0.02% w/v) at 6-h intervals failed to eliminate Pseudomonas aeruginosa, Proteus mirabilis, and Providencia stuartii from the bladder model. Escherichia coli, however, was susceptible to a second instillation provided that it was performed within 12 h. Supplementing chlorhexidine with EDTA and TRIS potentiated its activity against E. coli. Mandelic acid (1.0% w/v) was the most effective of the agents, double instillations eliminating all but Pr. mirabilis infections.

Scanning electron microscopy of bacterial biofilms on indwelling bladder catheters

Fifty Foley bladder catheters that had been indwelling for periods ranging from 3 to 83 days (mean 35 days) were examined for the presence of bacterial biofilm. Scanning electron microscopy on freeze-dried cross-sections and fixed, critical point-dried longitudinal sections revealed biofilm formation on the luminal surfaces of 44 of the catheters. Culture of urine samples and sonicates from catheters revealed that the prevalence of bacteriuria was less than that of catheter colonization. A wide range of nosocomial species were found colonizing the catheters, Escherichia coli being most often isolated. The bacterial composition of the biofilms ranged from single species to mixed communities containing up to four species. There was no relationship between the length of time that the catheter had been in situ and the extent of biofilm formation. The biofilms varied in thickness from 3 to 490 microns and were visible as layers of bacterial cells up to about 400 cells deep, embedded in a matrix.

Fimbriation, capsulation, and iron-scavenging systems of Klebsiella strains associated with human urinary tract infection

Thirty-two strains of Klebsiella pneumoniae and seven strains of Klebsiella oxytoca isolated from urinary tract infections in elderly adults were analyzed for capsular antigens, iron-scavenging systems, and fimbriation. All strains were capsulated. Twenty-seven different K antigens were identified among the strains, with no particular antigen dominating. All strains produced the iron-scavenging system enterochelin as analyzed by bioassay and DNA hybridization. In contrast, the aerobactin iron-sequestering system was not detected in any of the strains. All strains caused hemagglutination of tannin-treated human erythrocytes and reacted with an anti-type 3 fimbriae antiserum as well as in DNA hybridization with a type 3 fimbria-specific probe, indicating that the Klebsiella strains possessed this fimbrial type. Possession of type 1 fimbriae was analyzed by agglutination tests and by hybridization with DNA probes from two distinct Klebsiella type 1 fimbria gene clusters. Phenotypic expression of the type 1 fimbriae was found in 29 of 32 K. pneumoniae strains, whereas 30 strains reacted with either of the two type 1 fimbrial cluster DNA probes. In K. oxytoca, however, only three of seven strains expressed type 1 fimbriae and reacted with the DNA probes. The type 3 fimbriae were found to bind to a fraction of epithelial cells exfoliated in normal human urine, whereas the type 1 fimbriae bound strongly to urinary slime. No inhibitors of type 3 fimbrial binding were detected in human urine.

An assessment of antiseptic bladder washout solutions using a physical model of the catheterized bladder

The antibacterial activity of six antiseptic solutions formulated for use in bladder washout procedures has been examined in a simple model of the catheterized bladder. The experiments were carried out under conditions which examined the efficacy of the formulations against organisms that had recently contaminated the bladder urine. At cell densities of 10(4) cfu ml-1 all the solutions tested proved effective in eliminating bacteria from the bladder urine. Under conditions simulating heavy contamination (10(7)-10(8) cfu ml-1) however, only mandelic acid (1% w/v) eliminated the range of bacterial species commonly responsible for catheter-associated urinary tract infection.

Activity of antiseptics against biofilms of mixed bacterial species growing on silicone surfaces

As part of a programme to establish the relative merits of antiseptics that are used as bladder instillations to control urinary tract infections in patients with indwelling catheters, the activity of five such formulations were tested against dense (10(9) cfu/cm2) mixed biofilms composed of Citrobacter diversus, Pseudomonas aeruginosa and Enterococcus faecalis growing on silicone discs. All three species were resistant to chlorhexidine (200 mg/l) and povidone-iodine (1% v/v) in the biofilm mode of growth, whereas these agents rapidly eliminated viable cells from urine suspensions of the mixed community. Lactic acid (1% v/v) produced a 1 log reduction of the biofilm population within 30 min of exposure. The mandelic acid (1% w/v) and mandelic acid (0.5% w/v)/lactic acid (0.5% v/v) mixture proved to be the most effective in eliminating the biofilm organisms. It is suggested that these latter solutions should now be tested for efficacy in bladder washouts against urinary tract infections in catheterized patients.

Activity of some antiseptics against urinary tract pathogens growing as biofilms on silicone surfaces

The activity of chlorhexidine, mandelic acid and a mandelic/lactic mixture were tested against biofilms of four species of gram-negative nosocomial organisms that commonly infect the catheterized urinary tract. Cells growing on silicone discs were exposed to concentrations of agents used in bladder instillation. Citrobacter diversus biofilms proved to be sensitive to all three agents. Pseudomonas aeruginosa, Proteus mirabilis and Klebsiella pneumoniae all survived well in chlorhexidine but their viability was significantly reduced by the mandelic acid formulations. These results suggest that bladder instillations of mandelic acid or mandelic/lactic acids would be more effective than chlorhexidine in eliminating biofilms from catheter surfaces.

Activity of antiseptics against biofilms of mixed bacterial species growing on silicone surfaces

As part of a programme to establish the relative merits of antiseptics that are used as bladder instillations to control urinary tract infections in patients with indwelling catheters, the activity of five such formulations were tested against dense (10(9) cfu/cm2) mixed biofilms composed of Citrobacter diversus, Pseudomonas aeruginosa and Enterococcus faecalis growing on silicone discs. All three species were resistant to chlorhexidine (200 mg/l) and povidone-iodine (1% v/v) in the biofilm mode of growth, whereas these agents rapidly eliminated viable cells from urine suspensions of the mixed community. Lactic acid (1% v/v) produced a 1 log reduction of the biofilm population within 30 min of exposure. The mandelic acid (1% w/v) and mandelic acid (0.5% w/v)/lactic acid (0.5% v/v) mixture proved to be the most effective in eliminating the biofilm organisms. It is suggested that these latter solutions should now be tested for efficacy in bladder washouts against urinary tract infections in catheterized patients.

A double-blind comparative trial of short-term orally administered enoxacin in the prevention of urinary infection after elective transurethral prostatectomy: a clinical and pharmacokinetic study

A double-blind randomized comparative study was done to investigate the efficacy of enoxacin in the prevention of urinary infection after elective transurethral prostatectomy, as well as its ability to penetrate the prostate. A total of 40 patients received 200 mg. enoxacin and 40 received a placebo, given orally the night before the operation, 2 to 4 hours preoperatively and every 12 hours postoperatively for 36 hours. Urine samples for bacterial culture were obtained within 1 week preoperatively, at operation and at 48 hours, 5 days, and 2 and 6 weeks postoperatively. Samples of the serum and prostate were taken at operation and assayed for enoxacin levels. Of the placebo patients 15 had a urinary infection postoperatively (38 per cent) compared to 3 enoxacin patients (8 per cent) (p less than 0.01). Enoxacin penetrated well into prostatic tissue; the mean levels in tissue and serum were 3.1 +/- 1.8 mg. per kg. (standard deviation) and 1.26 +/- 0.48 mg. per l., respectively, with a mean tissue-to-serum ratio of 2.53 +/- 1.8.

Colonization of patients with spinal cord injury with Pseudomonas aeruginosa and Klebsiella pneumoniae at different institutions

Colonization of patients with Pseudomonas aeruginosa and Klebsiella pneumoniae was studied in patients with spinal cord injury at two institutions in Los Angeles County. The method of care of patients was similar at both institutions. A high prevalence of perineal colonization with P. aeruginosa and K. pneumoniae and similar serotypes of Pseudomonas were seen at both institutions. This colonization probably reflects the type of bladder management in patients with spinal cord injury. It would be of interest to examine other facilities to determine if colonization is influenced by techniques or local factors.

Chlorhexidine resistance among bacteria isolated from urine of catheterized patients

Seventy-four of 155 catheter specimens of urine yielded organisms resistant to chlorhexidine. The inhibitory effect of urine against chlorhexidine is reported.

The resistance of urinary tract pathogens to chlorhexidine bladder washouts

Isolates of Providencia stuartii, Pseudomonas aeruginosa, Proteus mirabilis, Klebsiella pneumoniae and Streptococcus faecalis from urinary-tract infections in spinally-injured patients together with Escherichia coli 10418 were challenged with chlorhexidine (200 mg l-1) in a model of a catheterized bladder under conditions which simulate the bladder washout technique. All species survived the antiseptic. Organisms growing on the wall of the bladder model appeared to be particularly resistant and electron microscopy showed that these cells were embedded in a protective glycocalyx. The effect of chlorhexidine bladder washouts on the bacterial flora in the urine of patients was also observed and shown to be minimal and temporary. Examination of urinary sediments from patients revealed the presence of micro-colonies of bacteria embedded in a polysaccharide matrix. We conclude that bladder washouts with chlorhexidine are not likely to eliminate established infections with organisms that occur in patients with indwelling bladder catheters.

A study of the skin flora of spinal cord injured patients

The skin flora of 11 spinally-injured patients was compared to that of 11 healthy control subjects. The perinea, groins, penile shafts and urethras of the patients were heavily colonized by a range of multi-drug resistant Gram-negative bacilli. Observations on patients from admission for up to 25 days suggest that the Gram-negative bacilli start to colonize the skin 2-3 days after admission. Some species, e.g., Citrobacter diversus and Escherichia coli appear as transient organisms while others such as Enterobacter aerogenes, Serratia marcescens, and Klebsiella pneumoniae seem to become stable skin residents. The relationship of the skin flora to the organisms causing urinary tract infections in these patients was studied.

Serial concentrations of C-reactive protein as an indicator of urinary tract infection in patients with spinal injury

C-reactive protein (CRP) was measured serially in 16 patients with an acute spinal injury. Twelve episodes of acute urinary tract infection (UTI) occurred during the study period. These were all associated with an increased concentration of CRP greater than 50 mg/l, which returned to normal after successful treatment. Thirteen episodes of asymptomatic bacteriuria associated with increased concentrations of CRP greater than 20 mg/l occurred, indicating tissue damage. More commonly, significant bacteriuria was associated with normal concentrations of CRP, and presumably, simple colonisation of the urinary tract, which, we suggest, does not require treatment with antibiotics. Serial measurement of CRP in patients with spinal injury may help distinguish between urinary tract colonisation and infection and be useful in monitoring the response to the treatment of clinical UTI.

Selective and differential medium for the primary isolation of members of the Proteeae

A new differential and selective medium for the isolation of members of the Proteeae, PIM (Proteeae isolation medium) agar, was developed and evaluated. The medium relies on the ability of all members of the Proteeae (with the exception of a very few Morganella morganii strains) to produce a dark brown pigment in medium containing DL-tryptophan. An additional differential property, tyrosine degradation, was also demonstrated by the medium. Members of the Proteeae appeared as dark brown colonies with a halo of clearing of fine tyrosine crystals when cultured on PIM agar. Occasional strains of Citrobacter sp. and Pseudomonas aeruginosa may degrade tyrosine, but none has the ability to produce dark brown pigmentation on PIM agar. Quantitative recovery studies showed that the addition of 5 mg of clindamycin per liter suppressed gram-positive bacteria without inhibiting any strains of the Proteeae. The addition of 100 mg of colistin per liter made the medium highly selective for strains of the Proteeae, but approximately 10% of the strains were not isolated, thus making this formulation unsuitable for general surveys of the occurrence of members of the Proteeae. PIM agar should aid the investigation of episodes of cross infection caused by members of the Proteeae and the isolation of the new species of the Proteeae recently described.

Systemic and topical antimicrobial agents in the prevention of catheter-associated bacteriuria and its consequences

Infection of the urinary tract is acknowledged to be the most common hospital infection, associated closely with the presence of an indwelling catheter. Patients are catheterized for a variety of reasons and for different periods of time, ranging from postoperative catheterization of a few days following urological surgery to the long-term catheterization over many months or years of patients who are unfit for operation, with spinal injuries or neuropathic bladders. The extent of the problem includes patients returning home infected, requiring catheterization before readmission to the hospital or needing nursing at home with a long-term catheter. The risks of infection and its complications as well as methods of control may differ between each group.

It is of fundamental importance to distinguish between patients who came to surgery with an existing infection and those with sterile preoperative urine. Other factors include recent previous catheterization and, importantly, the length of time the catheter is inserted. For the patient with sterile preoperative urine, postoperative bacteriuria seldom causes severe symptoms and can be treated with antibiotics or left to clear spontaneously after removal of the catheter. A minority of patients suffer consequences of their infection especially when bacteriuria starts before the catheter is removed postoperatively. Catheter removal often causes transient bacteremia, also induced by instrumentation or operation on infected urine, which may lead to serious complications, particularly of septicemia. In our experience in Bristol, about 1 in 4 patients admitted for urological surgery already has infected urine as defined by the presence of ≥105 bacteria/ml midstream urine or ≥=104 bacteria/ml catheter urine. Of those admitted with infected urine, 3 in 4 have a catheter already inserted compared with only 1 catheterized patient in 4 admitted to operation with sterile urine.

The urethral catheter--a review of its implication in urinary-tract infection

The research into acquisition of urinary-tract infection over the last few decades has established three ways in which organisms may gain access to the urinary tract of the catheterized patients: Firstly, during the process of passing the catheter into the bladder should complete asepsis not be observed; secondly by travelling along the urethra in the small, fluid-filled cavity between catheter and mucosa; Thirdly following contamination of the drainage system, along the inside of the catheter directly into the bladder. The relative importance of each route is not clear and is still the subject of much controversy but it would seem that all these routes have a part to play in allowing infection to develop. The risk of catheterized patients acquiring urinary-tract infection is so great that where possible catheterization should be avoided. The most important preventive measure which may be taken is to limit the duration of indwelling catheterization. In addition, a considerable amount of research has attempted to distinguish other factors which might affect the rate at which urinary-tract infection in the catheterized patient becomes established so that high-risk patients may be identified. The evidence indicates that the risk increases with duration of catheterization, age, length of hospital stay, immunosuppressant treatment, that it is greater in female than male patients and that a patient with a serious or fatal underlying disease is also more likely to develop bacteriuria. Finally, properties of the urine and the host defence mechanisms may affect the susceptibility of the individual to urinary-tract infection. Identification of the routes of infection and patients at risk is only part of the problem. The next stage is to formulate criteria for the care of catheterized patients which reduce the risk of infection to the absolute minimum and will hopefully go some way towards diminishing the unsatisfactory high levels of urinary-tract infection that are currently associated with indwelling catheterization.

Bacterial colonization of the lower urinary tract in women with long-term indwelling urethral catheter

The bacterial colonization of urethra and urine was studied over long periods in 16 hospitalized women with long-term indwelling bladder catheter. The cultured flora was polymicrobic and, except for Proteus mirabilis and Escherichia coli, rapidly changing. The colonization patterns showed marked inter-species variations. P. mirabilis was the species most commonly found, and in the urethra it was significantly more persistent than the other species. Unlike the other species, P. mirabilis was rarely found in urine without concomitant urethral growth. Prophylactic measures aimed to reduce the risk of permanent colonization by this pathogen, which is rendered particularly harmful by its urease production, should therefore be directed towards the urethra and the periurethral area.

Comparison of urine bag-changing regimens in elderly catheterised patients

Daily and weekly bag-changing regimens were compared in 12 elderly catheterised patients with reference to their clinical condition, leakage or blockage of the catheters, and the bacteriological state of the urine. Latex Foley catheters were used for the first 3 months and silastic catheters for the second 3 months of study. All patients had bacteriuria throughout the study, and the average number of bacterial species isolated from each specimen was 3.8. There were no significant clinical or bacteriological differences between the patients on daily and those on weekly bag change. Although significantly more episodes of pyrexia were recorded during latex than during silastic catheterisation there was no correlation between these episodes and the bacteriological state of the urine. Of the 9 courses of antibacterial treatment given during the 6 months, 7 were for indications other than urinary tract infection. There were no episodes of acute pyelonephritis. There were 148 episodes of pyrexia unrelated to any clinical symptoms or signs. Only 2 were treated with antibiotics; the remainder subsided without treatment.