Prevention of biofilm formation in dialysis water treatment systems

Identification and assessment of antimicrobial resistance bacteria in a hemodialysis water treatment system

The water treatment process is a vital factor for hemodialysis (HD) patients. This study aimed to assess the degree of contamination of HD water by bacteria at the HD center of Mohammedia, Morocco, in addition to evaluating the antimicrobial resistance of isolated bacteria. Fifty-four water samples were taken, the appropriate cultures were used to isolate the pathogenic bacteria, which were identified biochemically and molecularly by 16S RNA sequencing. Their susceptibility to antimicrobial drugs was determined by the disk diffusion method. Approximately 5.5% of water samples were above the norm. The isolated bacteria that colonized the HD systems were mostly Gram-negative bacilli, such as Stenotrophomonas maltophilia, Pseudomonas spp., and Burkholderia cepacian. Results of the antibiotics test showed remarkable resistance levels. Among Pseudomonas spp. and S. maltophilia, 10 strains were classified as multidrug-resistant (MDR), and 4 as extensively drug-resistant (XDR). The diversity of bacterial strains isolated in the water used for HD treatments, and their worrying resistance levels pose a significant risk to patients. For these reasons, an urgent need for periodic microbiological monitoring of water after each treatment step must be applied, and the treatment process should also be optimized.

An easy disinfection strategy for pipes connecting hemodialysis equipment

INTRODUCTION

A hemodialysis room has pipes connecting the console and central fluid equipment. While these pipes require disinfection, reports detailing disinfection strategies are unavailable. Therefore, we aimed to compare two easy disinfection strategies differing in sanitization frequency and sanitizer concentration.

METHODS

Reverse osmosis water (ROW) purifying equipment and six dialysis consoles were connected by 20 m of pipes. Only ROW flowed through these pipes, because the dialysate solution was constituted at each console. The pipes were sanitized by two strategies: (1) strong and monthly (hypochlorite concentration: 100 ppm) or (2) weak and weekly (5 ppm). Both strategies were easy because the sodium hypochlorite was simply added to the ROW tank. To estimate sanitization efficacy, endotoxin counts at the ROW tank outlet, the end of the pipe, and the pipe after the endotoxin-cutting filter in each console were measured monthly for six continuous months. These counts were compared between the two sanitization strategies.

RESULTS

The endotoxin counts at the ROW tank outlet and the end of the pipe were 0.004-0.017 and 0.012-0.081 EU/mL, respectively, in the strong and monthly strategy, and 0.001-0.003 and 0.001-0.005 EU/mL, respectively, in the weak and weekly strategy. The endotoxin counts at the pipe after the endotoxin-cutting filter were less than 0.001 EU/mL during the study period in both strategies.

CONCLUSION

A weekly disinfection strategy was more effective than a monthly one, despite the lower hypochlorite concentration. The present study suggests that frequency is the most important factor in the disinfection of pipes in a dialysis room.

Single-species (bacterial, fungal, or mycobacterial) biofilms or dual-species (mycobacterial-fungal) biofilms formed in dialysis fluids

Continuous hemodialysis system monitoring is necessary to prevent microorganism growth and health problems. This study evaluates single- and dual-species biofilm formation in microtiter plates by using dialysis solutions under aerobiosis or 5% CO₂ atmosphere. Escherichia coli, Pseudomonas aeruginosa, Staphylococcus epidermidis, Candida parapsilosis sensu lato, and Mycobacterium smegmatis produce single-species biofilms in all dialysis solutions in both oxygenation conditions. Dual-species biofilm cultures grown at 5% CO₂ atmosphere and in dialysate containing glucose reveal that M. smegmatis benefits from its association with C. parapsilosis. The dialysate and its constituent solutions support the growth of all the mono-species and the inter-kingdom mycobacterial/yeast biofilms in both aerobiosis and microaerophilic conditions.

A Pure Life: The Microbial Ecology of High Purity Industrial Waters

The microbial ecology of various natural environments has been an active area of research since the earlier part of the twentieth century. Remote and sometimes extreme environments such as the deep ocean and the deep terrestrial subsurface have revealed a remarkable array of microorganisms. The majority of these environments are nutrient limited, and microorganisms-principally, bacteria-have developed a number of survival strategies that enable their survival and, in some cases, replication. While planktonic microorganisms exist in oligotrophic environments, the predominant mode of survival and growth is associated with biofilms. There are a number of similarities between the physicochemistry of industrial water systems and some natural aquatic ecosystems, and these similarities extend to the microbial populations and the survival mechanisms that are employed. The "starvation-survival" mechanisms, including biofilm formation, may be associated with deleterious effects on industrial water systems. These effects include heat transfer inhibition, microbially influenced corrosion, and contamination of various products manufactured in a wide array of industries. Biological fouling of industrial water systems has significant direct and indirect (through antimicrobial chemical applications) impacts on engineered materials and on the etiology of some waterborne diseases. This review provides an overview of the microbial ecology of purified waters and discusses the impacts of biological activity on industrial systems.

Prevent infection linked to the dialysis water in a hemodialysis center in Fez city (Morocco)

Background

Water treatment systems are a critical variable in dialysis therapy. Rigorous control of hemodialysis water quality is particularly important in order to guarantee a better quality of life of the hemodialysis patients. The objective of the study was to evaluate the chemical, microbiological quality and antimicrobial resistance of bacteria isolated from water and dialysate in a public HD center.

Methods

Fifty five samples of water and dialysate were collected weekly over a period of 4 months. The samples were collected from 4 points in the distribution loop. The microbiological and chemical analyses were performed according to our national standards. Antimicrobial susceptibilities patterns of isolated bacteria were determined by disk diffusion method.

Results

The chemical and microbiological parameters in all dialysis water and dialysate samples are in accordance with national standards. However, 70 Gram-negative bacteria were identified: Pseudomonas sp, Ochrobactrum antropi and Burkholderia cepacia, isolated at 52.8%, 12.8% and 17% simultaneously. Fourteen per cent of the isolates were resistant to three or more antibiotics. All resistant bacteria belong to the genus of Pseudomonas, 80% were resistant to tetracycline and to co-trimoxazole, 30% to ceftazidime. No colistin and imipenem resistance was observed.

Conclusion

To avoid a health risk due to bacterial contamination, an adequate system for water treatment, disinfection of the hemodialysis system and microbiological monitoring of the water and dialysate are necessary.

The bacterial biofilms in dialysis water systems and the effect of the sub inhibitory concentrations of chlorine on them

INTRODUCTION

The presence of bacteria in the form of biofilms poses a problem in the fluid pathways of haemodialysis plants and procedures which are aimed to detach and neutralize biofilms are necessary to improve the patient safety and the quality of the healthcare. The present study was therefore aimed at isolating the organisms which colonized dialysis water systems as biofilms, as well as to study the effect of the sub inhibitory concentrations of chlorine on the biofilms which were produced by these isolates.

METHODS

Swabs were used to collect the biofilms which were produced on the internal surface of the dialysis tubing from the dialysis units. This study was conducted at the Department of Microbiology, Kasturba Medical College (KMC), Mangalore, India. The cultures were performed on MacConkey's agar and blood agar. The organisms which were isolated were identified and antibiotic sensitivity tests were performed. The biofilm production was done by the microtitre plate method of O'Toole and Kolter. The biofilm production was also studied in the presence of sub inhibitory concentrations of chlorine.

RESULTS

Acinetobacter spp and Pseudomonas aeruginosa were the two predominant organisms which colonized the dialysis water systems as biofilms. The sub inhibitory concentrations of chlorine did not bring about any decrease in the biofilm production by the isolates. On the contrary, there was an increase in the biofilm production.

CONCLUSION

Our study highlighted the importance of using appropriate methods to improve the quality of the water in dialysis units. This in turn, may help in reducing the biofilm formation in the water systems of dialysis units and thus, contribute to the prevention of hospital acquired infections in the patients who need haemodialysis.

Microbiological quality and quality control of purified water and ultrapure dialysis fluids for online hemodiafiltration in routine clinical practice

During online hemodiafiltration, patients are directly infused with sterile substitution solutions to maintain fluid balance. Adequate water treatment and a well-organized quality control process are essential to provide non-pyrogenic fluids with consistent optimal quality. We sought to assess water quality, the water treatment system, and the methods for surveillance of microbiological water quality in 10 Dutch dialysis centers that routinely treat patients with hemodiafiltration. Microbiological monitoring results (micro-organisms and endotoxins) were collected over a 1-year period representing 11,258 hemodiafiltration sessions covering 97 patients. In all centers, water purification was based on a reverse osmosis module in combination with a second reverse osmosis and/or an electrodeionizer. All centers regularly and routinely monitored the microbiological purity of the dialysis water with adequate analytical methods but with variable monitoring frequency. Microbiological assessments were compliant with reference quality levels in 3923 of 3961 samples. Our study suggests that non-pyrogenic substitution fluids can be produced online for a prolonged period of time. It is likely that the current Dutch Quality of Care Guideline has contributed to high-quality water treatment and a well-organized control process.

A microbiological survey of bicarbonate-based replacement circuits in continuous veno-venous hemofiltration

OBJECTIVE

The potential for clinically significant transfer of pyrogen-inducing material in dialysate and substitution fluids is well recognized in the setting of chronic hemodialysis and hemodiafiltration and has led to the establishment of strict standards for microbiological purity. Preliminary evidence has indicated the potential for fluid contamination in continuous renal replacement therapy, and although the scale of the problem in contemporary, industry-standard equipment is unclear. We aimed to define the microbial integrity of modern continuous veno-venous hemofiltration (CVVH) replacement fluid circuitry.

DESIGN

Twenty-four CVVH replacement fluid circuits (mean lifespan, 34.2 hours; range, 4-86) were studied at completion of therapy.

SETTING

The integrated critical care unit and cardiothoracic intensive care unit of the Freeman Hospital, Newcastle upon Tyne, United Kingdom, between January and August 2007.

SUBJECTS

Patients with renal failure receiving treatment with CVVH.

INTERVENTIONS

Nil.

MEASUREMENTS

Culture and endotoxin assays of replacement fluid, culture of endoluminal swabs, and electron microscopy of harvested tubing.

MAIN RESULTS

Of the 24 replacement fluid cultures, nine (mean lifespan 32.8 hours, range 5-79) breached European Pharmacopoeia standards for ultrapure water (<0.1 colony-forming units/mL). One of 24 endotoxin measurements breached European Pharmacopoeia standards (<0.03 endotoxin units/mL). Internal tubing cultures were negative, but electron microscopy revealed 13 of the 24 collected tubing samples to be contaminated with biofilm. Only seven of the 24 studied circuits proved to be free from microbial contamination.

CONCLUSIONS

We have confirmed frequent breaches of microbial integrity in industry-standard, bicarbonate-based CVVH, indicating the potential for added risk to the vulnerable, critically ill patient. These findings are of particular concern given the need for systemic infusion of replacement fluid. Measures to reduce the levels of contamination and their impact are discussed.

Biofilms in nephrology

BACKGROUND

Biofilms are bacterial communities ubiquitous to moist environments. Biofilm formation is a factor in the development and persistence of infectious diseases. In clinical nephrology, biofilms influence the development of kidney stones and affect dialysis systems, including peritoneal and central venous catheters. Biofilms also play critical roles in persistent and resistant renal and urinary tract infections.

OBJECTIVE

To describe the physiology of biofilms and potential effects of biofilms upon infectious diseases, focusing on the role of biofilms in kidney stones, indwelling catheters and dialysis equipment.

METHODS

A literature search with Medline to identify pertinent English language articles published up to early 2008 using the keywords biofilm, nephrology, renal, calculi and infection.

RESULTS/CONCLUSION

Biofilms are ubiquitous in clinical nephrology and play a role in the pathogenesis of resistant infections. Strategies for reducing the effects of biofilms in nephrology are described.

Microbiological quality of water and dialysate in a haemodialysis unit in Ponta Grossa-PR, Brazil

AIMS

The objective of the study was to determine the microbiological quality of samples of water and dialysate in a haemodialysis unit.

METHODS AND RESULTS

Seventy-two samples each of water and dialysate were collected during November 2003 to April 2004. The following microbiological analyses were performed: test for total and faecal coliforms, which produced negative results for all the samples; counts of total heterotrophic bacteria, where three samples of water and two of dialysate showed levels higher than those permitted by national standards; and endotoxin assay, which revealed high quantities only in samples of water that preceded reverse osmosis. Nonfermenting Gram-negative bacteria were identified in 54 samples of dialysate and in 26 samples of water. The test for adhesion to an inert surface showed that various bacteria were capable of forming biofilms. Twenty-seven per cent of the bacteria were resistant to sodium hypochlorite at 500 ppm for 10-min contact time. Sixty per cent of the isolates were resistant to three or more antibiotics.

CONCLUSIONS

Water and dialysate can be a source of infection for patients who need haemodialysis.

SIGNIFICANCE AND IMPACT OF THE STUDY

An adequate system for water treatment, disinfection of the haemodialysis system and microbiological monitoring of the water and dialysate are necessary to reduce bacteraemia and pyrogenia outbreaks.

Online Hemodiafiltration

Online hemodiafiltration (HDF) is an extracorporeal technique for solute removal in renal failure, which takes advantage of an enhancement of convective treatment by the large amount of ultrapure nonpyrogen dialysate being used for substitution of the ultrafiltered volume. It offers many advantages aside from its safe inflammatory profile, which is attributable to the use of ultrapure dialysate and highly biocompatible dialysis membranes. Due to an improved convective clearance, significantly increased removal of large or protein-bound uremic retention solutes can be achieved, with a potential benefit on cardiovascular morbidity and mortality. Recent observational data indicate that online HDF offers a survival advantage even after adjustment for comorbidity and dialysis efficiency. Research has been ongoing to maximize further the effectiveness of the technique by new technical innovations such as transmembrane-pressure feedback control or mid-dilution online HDF.

Biofilm: its relevance in kidney disease

Biofilm/bioslime is a complex, dynamically interactive multicellular community protected within a heterogeneous exopolysaccharide matrix. Its formation results in the genesis or perpetuation of infection, enhancement of inflammation, and tissue damage or death. Industrial financial losses result from biofilm/bioslime formation; however, the consequences in the medical realm are equally devastating. The relation of biofilm to patients with chronic kidney disease is often covert and extends beyond the colonization of hemodialysis circuits and vascular accesses. Urinary tract device- and vascular access-related biofilms may also increase the burden of cardiovascular risk borne by chronic kidney disease patients, synergizing with the chronic inflammatory state already incurred by these individuals. Current anti-infective strategies are aimed at rapidly killing planktonic forms of microorganisms without specifically targeting the sessile forms that perpetuate their planktonic brethren. Future treatments of infections must ultimately target these reservoirs of infection aiming for their complete eradication. Presently, included among these novel weapons of microdestruction are molecular blockading techniques, electrical enhancement of anti-infectives, and bacterial interference. Nonetheless, the best approach against biofilm formation remains the prevention of microbial colonization, which can be largely by sterile handling of patient-related devices, the most well-established biofilm reservoirs.

The Importance of Water Quality and Haemodialysis Fluid Composition

Treatment of renal failure by haemodialysis uses dialysis fluid to facilitate the normalization of electrolyte and acid base abnormalities and the removal of low molecular weight uraemic compounds present in the plasma such as urea. The dialysis fluid is a continuously produced blend of treated tap water and a concentrated solution containing electrolytes, buffer, and glucose. The water used originates as drinking water but undergoes additional treatment. Recent surveys have indicated that the chemical and microbiological content of such water frequently fails to meet the requirements of established standards, and its bacterial content arising from the presence of a biofilm in the water distribution network or the hydraulic circuit of the dialysis machine is a contributory factor to the chronic inflammatory state in patients undergoing regular dialysis. The composition of the dialysis fluid plays an important role in the modulation of complications associated with end-stage renal disease, as well as those associated with the treatment itself. The avoidance of complications arising from water contaminants requires a constant and vigorous attention to water quality, whilst with the composition of electrolytes and buffer there is a trend towards greater individualization to provide a high degree of treatment tolerance.

Growing and analyzing biofilms in fermenters

One of the most daunting challenges of biofilm research is comparing experimental results produced by multiple laboratories, each of which uses different techniques to generate, analyze, and interpret biofilm data. The heterogeneity inherent to biofilm communities contributes to the difficulty in obtaining reproducible results between experiments within a single laboratory, but the problem is compounded further by a lack of standardization in techniques. A number of biofilm culture methods are presented in this unit to provide a set of standards for biofilm study. Each model system differs in growth conditions, applied variables, and experimental output, all of which must be carefully considered when designing an experiment and, most critically, during data interpretation. In this unit, two methods of biofilm culture that are known to reliably provide reproducible, statistically clean results in determining the viability and antimicrobial susceptibility of biofilm communities are described. The spinning disc model provides multiple biofilm samples from the same biofilm reactor, significantly reducing data variability. The tube biofilm method, in addition to providing this benefit, can be used for expression analysis, and thus can yield informative data on both macro- and micro-scales. These methods also utilize continuous culture, or chemostat, conditions to maintain a quasi-steady state.

A New Procedure Allowing the Complete Removal and Prevention of Hemodialysis Biofilms

Most currently used disinfectants for dialysis machines have a good bactericidal efficacy on biofilms but leave dead cells on the surface. This contributes to the regrowth of biofilm and the release of pyrogens. A new anti-biofilm procedure consisting of sequential treatment combining enzymes and detergents is able to detach adherent cells. The efficacy of this procedure was assessed both in vitro and in reality. For in vitro studies, a biofilm model was set up. Studies were also performed in reality in a clinically used dialysis machine. Biofilm removal was first monitored by image analysis. Then, the biomass was detached by scraping and quantified by plate counts and endotoxin level measurement. Treated samples were compared to untreated control samples. The procedure led to the complete detachment of the biomass, both in vitro and in the reality situation. The aim of this procedure is to replace or complete the usual disinfection methods for medical devices.

Dialysis water as a determinant of the adequacy of dialysis

Hemodialysis patients are exposed to large volumes of water in the form of dialysate. Contaminants from the dialysate may cross the dialyzer membrane into the blood and have the potential to compromise the adequacy of dialysis. Several chemicals found commonly in drinking water have long been known to be toxic to hemodialysis patients. More recently, it has become apparent that even low levels of bacterial products in dialysate may adversely impact dialysis adequacy through their ability to stimulate an inflammatory response. Minimum levels of water and dialysate quality have been recommended to protect patients from chemical and microbiologic contaminants. Complying with these recommendations requires an appropriately designed water purification and distribution system, combined with a surveillance program designed to maintain dialysate quality.

POOR NUTRITIONAL STATUS AND INFLAMMATION: Ultrapure Dialysate

To prevent pyrogenic reactions during hemodialysis, it is recommended that bacteria and endotoxin in dialysate not exceed 100-200 colony forming units (CFU)/ml and 0.25-2 endotoxin units (EU)/ml, respectively. While these limits are adequate to prevent acute pyrogenic reactions, data are accumulating to suggest they may not prevent stimulation of chronic inflammation in hemodialysis patients. Fragments of endotoxin and other bacterial products capable of stimulating immune cells cross low-flux and high-flux membranes in vitro. In clinical studies, use of ultrapure dialysate (bacteria < 0.1 CFU/ml and endotoxin < 0.03 EU/ml) is associated with lower concentrations of inflammatory markers and acute phase reactants than are observed with dialysate meeting current quality recommendations. Moreover, observational studies suggest a link between clinical outcomes and dialysate purity. Treatment of patients with ultrapure dialysate is reported to improve nutritional status, increase responsiveness to erythropoietin, slow the decline in residual renal function, lessen cardiovascular morbidity, and decrease the incidence of beta(2)-microglobulin amyloidosis. To date, however, none of these studies has shown a cause-and-effect relationship between dialysate purity and outcome. Further, there are no data defining the concentration dependence of outcomes on dialysate purity and the relative importance of dialysate purity as a trigger of inflammation remains unclear. While the technology exists to routinely provide ultrapure dialysate, controlled clinical trials are still needed to answer the question of whether or not introducing ultrapure dialysate into routine clinical practice represents an efficient use of limited resources in terms of decreasing inflammation and improving outcomes in hemodialysis patients.