Is biofilm a cause of silent chronic inflammation in haemodialysis patients? A fascinating working hypothesis

Gianni Cappelli1, Ciro Tetta2 and Bernard Canaud3

1 Department of Nephrology, Dialysis and Transplantation, University of Modena, Modena, Italy, 2 Fresenius Medical Care Deutschland GmbH, Bad Homburg, Germany and 3 Nephrology and Renal Research and Training Institute, CHU Montpellier, Montpellier, France

Correspondence and offprint requests to: Professor Bernard Canaud, Nephrology, Lapeyronie University Hospital, CHU Montpellier, 371, Avenue du Doyen G. Giraud, 34925 Montpellier, France. Email: b-canaud{at}chu-montpellier.fr

Keywords: biofilm; chronic inflammation; C-reactive protein; haemodialysis adequacy



   Introduction
 Top
 Introduction
 Vascular access in haemodialysis...
 Haemodialysis monitors
 Conclusions
 References
 
Knowledge of biofilm formation and its biological role in chronic subclinical inflammation has largely evolved over the past years [1–5]. The development of a biofilm is a very effective way for bacteria to survive facing hostile conditions and to resist biocides and antimicrobial substances. The initial event in biofilm formation is the adhesion of microbes to surfaces. The surface properties of medical devices are usually modified by a conditioning film of organic material. The effect of single blood proteins or of whole blood itself depends on bacterial strains. Fibrinogen and fibronectin both enhance Staphylococcus aureus binding and inhibit Staphylococcus epidermidis or Gram-negative bacteria adherence, while whole blood promotes Pseudomonas aeruginosa biofilm formation [6].

Biofilm is not a static simple matrix made of homogeneous slime embedding bacteria. This sessile multicellular community is a dynamic complex system made of exopolysaccharide matrix embedding living microorganisms with a phenotype modified from planktonic (free-floating) bacteria. Biofilm is a living material that evolves according to local microenvironmental conditions (hydrodynamic and biochemical conditions, thickness, shear stress and possibly others). Biofilm has a spatial heterogeneity (channels, towers) that seems to be linked to the type of bacteria and may differ in relation to oxygen limitation, pH, nutrient access and growth rates.

However, despite these important acquisitions, the role of biofilm in haemodialysis patients is undefined. At present, we are unable to define the extent and the incidence of biofilm formation in the haemodialysis population. No method exists to detect biofilm in vivo and to ascertain its eradication. In principle, bacteria are often shown to form biofilm using ‘extreme’ and unrealistic experimental conditions. Detection of biofilm is usually performed by surface ultrastructural analysis alone or in combination with methods to stain the bacterial nuclear DNA using membrane-permeable or impermeable fluorochromes (to detect dead or live bacteria, respectively). In this editorial, we will describe several potential sites of bacterial contamination and possibly of biofilm formation in haemodialyis patients, such as the vascular access (arterio-venous fistula and graft or venous catheters) and the hydraulic circuit of the water treatment and of haemodialysis monitors.



   Vascular access in haemodialysis patient
 Top
 Introduction
 Vascular access in haemodialysis...
 Haemodialysis monitors
 Conclusions
 References
 
Vascular access offers an excellent way for bacteria to invade the bloodstream of haemodialysis patients. Vascular access (arteriovenous or venovenous) represents a door open to the internal milieu three times a week. Arteriovenous vascular accesses (native arteriovenous fistula and synthetic graft fistula) are usually located superficially under the skin, close to an area where bacteria proliferate quite easily. Needle insertion breaks the skin barrier and facilitates the penetration of topical bacteria into the bloodstream. Bacteria may circulate either as a planktonic form to be finally cleared by the reticuloendothelial system (particularly in the lungs and spleen) or they may adhere to the vascular endothelium or to a foreign surface (e.g. synthetic prosthetic graft or catheter polymer). At this stage, immobilized bacteria modify their phenotype and start producing slime matrix embedding living bacteria [7]. In principle, this stage represents the first step of biofilm formation. Native arteriovenous fistulae are obviously less exposed to biofilm formation than synthetic materials [8]. In most cases, the penetration of bacteria into the bloodstream will induce an acute febrile event. An intact vascular endothelium possesses efficient host defence mechanisms capable of preventing adhesion and of neutralizing adherent bacteria. Stagnant zones are often associated with an altered endothelium and partial thrombosis, such as in the case of a ‘false aneurysm’. Here, bacteria may adhere to the endothelium, possibly forming biofilm. Thus, an inflammatory ‘false aneurysm’ on an arteriovenous fistula should always be removed under antibiotic therapy. On the other hand, synthetic graft material (e.g. PTFE) or central venous catheters made of synthetic polymer (poyurethane or silicone rubber) are clearly more exposed to bacteria [9]. Synthetic materials have none of the anti-adhesive or anti-bacterial properties of the endothelium. The material surface usually consists of crevices and cracks that facilitate adhesion of bacteria. Moreover, synthetic materials promote the adsorption of circulating proteins (albumin and clotting proteins) on their surfaces, thus enhancing bacterial adhesion and proliferation. Flow stagnation in venous catheters, which occurs during the inter-dialytic period, may offer ideal conditions to immobilized bacteria for proliferation and biofilm formation

As we stated above, there is no method to detect the presence of biofilm. Even if biofilm could be detected subsequently by surface morphological analysis, biofilm in the vascular access may have remained clinically asymptomatic. Occasionally, it may be suspected by the sudden onset of a febrile reaction occurring during a haemodialysis session in the absence of overt signs of infection. This type of reaction illustrates the fact that bacteria may be released from the biofilm, possibly in the presence of facilitating factors such as a high blood shear stress leading to de novo bacteraemia. Biofilm is the source of chronic, subclinical inflammation due to the repeated stimulation of monocytes/macrophages. The release of pro-inflammatory cytokines may not only provide a strong stimulus for a sustained acute phase response, increased plasma levels of C-reactive protein and erythropoetin resistance, but may also favour activation of the coagulation pathways leading to vascular access thrombosis [10,11].

Accordingly, it is of paramount importance to prevent the penetration of bacteria into the bloodstream at the time of connection (or disconnection) of the patient to the haemodialysis monitor. This risk underlines the critical role of nursing care and clinical practice in managing the vascular access and in preventing bacterial contamination [12,13]. PTFE graft vascular accesses are more exposed than native fistulae to bacterial contamination, the relative risk being estimated at around three times higher [14]. Interestingly, such a risk persists in thrombosed PTFE prosthesis. It is therefore recommended to remove an unused graft to prevent chronic inflammation in haemodialysis patients [14]. Venous accesses (catheters and port devices) are more exposed to bacterial implantation. Biofilm formation is likely to occur in prolonged stagnation (e.g. during the inter-dialytic period). This risk is clearly illustrated by the fact that the incidence of symptomatic infections is seven times higher with catheters than with native arteriovenous fistulas [15]. Moreover, clots formed at the tip of the unused catheter during the inter-dialytic period provide a perfect nutrient medium for bacterial proliferation and possibly biofilm formation. Interestingly, it has been shown that the regular use of a catheter locking solution, with a dual action antithrombotic and antimicrobial venous port catheter device, prevents the formation of biofilm (W. Costerton, personal communication) and reduces the incidence of bacteraemia [16–18]. Dual action antithrombotic and antimicrobial locking solutions offer an attractive means to prevent catheter colonization and biofilm formation in permanent catheters providing the safety of the solution is ensured [19]. Catheter locking solutions deserve further control studies in permanent catheters before they can be proposed as a routine pre-emptive therapy for catheter-related morbidity [20].



   Haemodialysis monitors
 Top
 Introduction
 Vascular access in haemodialysis...
 Haemodialysis monitors
 Conclusions
 References
 
The highest risk of bacterial contamination and biofilm formation in haemodialysis monitors may derive from the water tubing connecting the reverse osmosis–water distribution loop with the individual haemodialysis monitors. In this critical part of the system, a biofilm may well form in the stagnant phases (e.g. during the night). These connecting lines need to be included in routine disinfection procedures and replaced on a regular basis. In order to reduce biofilm formation, disinfection of the entire water distribution system, including the connecting tubes and the dialysis monitor, is required on a regular basis. Regularly means at least weekly, better daily. Disinfection can be done using chemicals, ozone or heat [21,22]. Pyrogens released from biofilm include not only endotoxins but also bacterial DNA fragments which are small, trigger Toll-like receptors on monocytes and induce cytokine production leading to an inflammatory response [23]. Bacterial DNA fragments are not removed from contaminated dialysate by ultrafiltration. Therefore, installation of ultrafilters in the dialysate line does not replace the need for disinfection of the entire water distribution system.

Haemodialysis monitors represent the final link of the water system chain transforming tap water into dialysate. Haemodialysis monitors have additional reasons that expose them to bacterial proliferation and biofilm formation: the presence of basic and acid concentrate solutions and inlets, dialysate connectors and the drain itself.

Once contamination has occurred, biofilm formation depends on the physical properties (i.e. design, length and water flow velocity) and on the material surface properties (polymer and roughness) of the hydraulic circuit (Figure 1A and B). Disinfection is the only way to prevent bacterial proliferation. However, all disinfection protocols are validated in relation to microbial killing and not to biofilm prevention and eradication [22,24].



View larger version (114K):
[in this window]
[in a new window]
 
Fig. 1. (A) Bacteria adhering onto the surface of a haemodialysis tubing and starting the formation of a biofilm. (B) Bacteria and biofilm trapped in a crystal network made of calcium and magnesium carbonate salt in a dialysis tubing.

 
According to medical device regulations, it is the manufacturer's responsibility to determine proper disinfection methods and protocols. In routine practice, non-compliant or inadequate operative protocols may lead to inappropriate disinfections. Re-contamination may occur during technical maintenance controls. Re-contamination may also derive from a persisting bacterial focus, depending on the mode of disinfection, technical design of the machine, duration of haemodialysis and flora in the dialysate [25,26]. A stable microbial contamination causes biofilm, and biofilm itself decreases disinfection treatment effectiveness on both bacteria and endotoxins [5,21,23,26–28].

A high level of decontamination for haemodialysis machines is recommended nowadays when ultrapure dialysate is required not only for on-line treatment but also for standard dialysis. Ultrapure dialysate with a final ‘on-line’ dialysate ultrafiltration represents a quality assurance method and enables high standard levels of purity [25].

Quality controls and surveillance programmes are of paramount importance to ensure production and delivery of an ultrapure dialysate. Disinfection procedures may be validated from results obtained through a regular monitoring of incoming water and dialysate. The most recent guidelines stress all these aspects and introduce the concept of quality assurance in dialysis to ensure patient safety [26].



   Conclusions
 Top
 Introduction
 Vascular access in haemodialysis...
 Haemodialysis monitors
 Conclusions
 References
 
Despite the large degree of uncertainty as to the incidence of biofilm formation in haemodialysis, several sites are definitively exposed to bacterial contamination and proliferation. If biofilm is formed, it would be very resistant to conventional disinfection methods. At present, all efforts should be made to prevent bacterial contamination and colonization. New methods are expected and required to help in detecting biofilm formation in the vascular access and dialysate tubings in order to prevent and to treat inflammatory complications in haemodialysis patients.

Future studies hopefully should define whether biofilm formation may be a cause of chronic inflammation—often a ‘silent’ (subclinical) process. This is a new challenge to establish haemodialysis adequacy. It will introduce a new dimension in the treatment, i.e. dialysis quality adequacy.



   Acknowledgments
 
Conflict of interest statement. C. Tetta is a full-time employee of Fresenius Medical Care Deutschland GmbH.



   References
 Top
 Introduction
 Vascular access in haemodialysis...
 Haemodialysis monitors
 Conclusions
 References
 

  1. Costerton JW, Stewart PS, Greenberg EP. Bacterial biofilms: a common cause of persistent infections. Science 1999; 284: 1318–1322[Abstract/Free Full Text]
  2. Costerton W, Veeh R, Shirtliff M, Pasmore M, Post C, Ehrlich G. The application of biofilm science to the study and control of chronic bacterial infections. J Clin Invest 2003; 112: 1466–1477[Abstract/Free Full Text]
  3. Khoury AE, Lam K, Ellis B, Costerton JW. Prevention and control of bacterial infections associated with medical devices. ASAIO Trans 1992; 38: M174–M178
  4. Man NK, Degremont A, Derbord JC, Collet M, Vaillant P. Evidence of bacterial biofilm in tubing from the hydraulic pathway in the hemodialysis system. Artif Organs 1998; 22: 596–600[CrossRef][ISI][Medline]
  5. Cappelli G, Ballestri M, Perrone S, Ciuffreda A, Inguaggiato P, Albertazzi A. Biofilms invade nephrology: effect in hemodialysis. Blood Purif 2000; 18: 224–230[CrossRef][ISI][Medline]
  6. Murga R, Miller JM, Donlan RM. Biofilm formation by gram-negative bacteria on central venous catheter connectors: effect of conditionings films in a laboratory model. J Clin Microbiol 2001; 39: 2294–2297[Abstract/Free Full Text]
  7. De Lancey Pulcini E. Bacterial biofilms: a review of current research. Néphrologie 2001; 22: 439–441[ISI][Medline]
  8. Bergamini TM, Bandyk DF, Govostis D, Kaebnick HW, Towne JB. Infection of vascular prostheses caused by bacterial biofilms. J Vasc Surg 1988; 7: 21–30[CrossRef][ISI][Medline]
  9. Delorme JM, Guidoin R, Canizales S et al. Vascular access for hemodialysis: pathologic features of surgically excised ePTFE grafts. Ann Vasc Surg 1992; 6: 517–524[Medline]
  10. Canaud B, Senecal L, Leray-Moragues H et al. Vascular access, an underestimated cause of inflammation in hemodialysis patient. Néphrologie 2003; 24: 353–358[ISI][Medline]
  11. Muirhead N, Hodsman AB. Occult infection and resistance of anaemia to rHuEpo therapy in renal failure. Nephrol Dial Transplant 1990; 5: 232–234[ISI][Medline]
  12. Canaud B. Haemodialysis catheter-related infection: time for action. Nephrol Dial Transplant 1999; 14: 2288–90[Free Full Text]
  13. Mermel LA. Prevention of intravascular catheter-related infections. Ann Intern Med 2000; 132: 391–402[Abstract/Free Full Text]
  14. Hoen B, Paul-DauphinA, Hestin D, Kessler M. EPIBACDIAL: a multicenter prospective study of risk factors for bacteremia in chronic hemodialysis patients. J Am Soc Nephrol 1998; 9: 869–76[Abstract]
  15. Nassar GM, Fishbane S, Ayus JC. Occult infection of old nonfunctioning arteriovenous grafts: a novel cause of erythropoietin resistance and chronic inflammation in hemodialysis patients. Kidney Int 2002; 61 [Suppl 80]: 49–54[CrossRef]
  16. Sodemann K, Polaschegg HD, Feldmer B. Two years’ experience with Dialock and CLS (a new antimicrobial lock solution). Blood Purif 2001; 19: 251–4[CrossRef][ISI][Medline]
  17. Allon M. Prophylaxis against dialysis catheter-related bacteremia with a novel antimicrobial lock solution. Clin Infect Dis 2003; 36: 1539–1544[CrossRef][ISI][Medline]
  18. McIntyre CW, Hulme LJ, Taal M, Fluck RJ. Locking of tunneled hemodialysis catheters with gentamicin and heparin. Kidney Int 2004; 66: 801–805[CrossRef][ISI][Medline]
  19. Polaschegg HD, Sodemann K. Risks related to catheter locking solutions containing concentrated citrate. Nephrol Dial Transplant 2003; 18: 2688–2690[Free Full Text]
  20. Betjes MG, van Agteren M. Prevention of dialysis catheter-related sepsis with a citrate-taurolidine-containing lock solution. Nephrol Dial Transplant. 2004; 19: 1546–1551[Abstract/Free Full Text]
  21. Smeets E, Kooman J, van Der Sande F et al. Prevention of biofilm formation in dialysis water treatment systems. Kidney Int 2003; 63: 1574–1576[CrossRef][ISI][Medline]
  22. Lonnemann G. When good water goes bad: how it happens, clinical consequences and possible solutions. Blood Purif 2004; 22: 124–129[CrossRef][ISI][Medline]
  23. Schindler R, Beck W, Deppisch R et al. Short bacterial DNA fragments: detection in dialysate and induction of cytokines. J Am Soc Nephrol 2004; 15: 3207–3214[Abstract/Free Full Text]
  24. Cappelli G, Sereni L, Scialoja MG et al. Effects of biofilm formation on haemodialysis monitor disinfection. Nephrol Dial Transplant 2003; 18: 2105–2111[Abstract/Free Full Text]
  25. Marion-Ferey K, Pasmore M, Stoodley P, Wilson G, Husson GP, Costerton JW. Biofilm removal from silicone tubing: an assessment of the efficacy of dialysis machine decontamination procedures using an in vitro model. J Hosp Infect 2003; 53: 64–71[CrossRef][ISI][Medline]
  26. Kolmos HJ. Bacterial contamination of heat-sterilized, heat-disinfected and chemically-disinfected haemodialysis monitors. Acta Pathol Microbiol Scand 1978; 86: 101–106.
  27. Oie S, Kamiya A, Yoneda I et al. Microbial contamination of dialysate and its prevention in haemodialysis units. J Hosp Infect 2003; 54, 115–119[CrossRef][ISI][Medline]
  28. Penders C, Kooman JP, Stobberingh EE, van Der Sande FM, Frederik PM, Leunissen KM. Does ultra-pure dialysate prevent the development of biofilm in dialysis therapy? Nephrol Dial Transplant 2001; 16: 1522–1524[Free Full Text]
  29. European Best Practice Guidelines for Haemodialysis. Dialysis fluid purity; appendix: quality assurance process. Nephrol Dial Transplant 2002; 17 [Suppl 7]: 60–62




This Article
Extract
FREE Full Text (PDF)
All Versions of this Article:
20/2/266    most recent
gfh571v1
Alert me when this article is cited
Alert me if a correction is posted
Services
Email this article to a friend
Similar articles in this journal
Similar articles in ISI Web of Science
Similar articles in PubMed
Alert me to new issues of the journal
Add to My Personal Archive
Download to citation manager
Search for citing articles in:
ISI Web of Science (1)
Disclaimer
Request Permissions
Google Scholar
Articles by Cappelli, G.
Articles by Canaud, B.
PubMed
PubMed Citation
Articles by Cappelli, G.
Articles by Canaud, B.