Proceedings of the ISPD 2001 — The IXth Congress of the ISPD June 26 – 29, 2001, Montréal, Canada Peritoneal Dialysis International, Vol. 21 (2001), Supplement 3
0896-8608/01 $3.00 + .00 Copyright © 2001 International Society for Peritoneal Dialysis Printed in Canada. All rights reserved.
EFFECT IN A RAT MODEL OF HEPARINIZED PERITONEAL DIALYSIS CATHETERS ON BACTERIAL COLONIZATION AND THE HEALING OF THE EXIT SITE
Yong-Lim Kim, Seong Cho, Jun-Chul Kim, Dong-Kyu Cho, Yong-Jin Kim,1 Olle Larm,2 Torbjorn Mathiesen,2 Bengt Lindholm,2 Jonas Bergström2
Division of Nephrology, Department of Internal Medicine, School of Medicine, Kyungpook National University, and Department of Pathology,1 Yeungnam University School of Medicine, Taegu, South Korea; and Divisions of Baxter Novum and Renal Medicine,2 Huddinge University Hospital, Karolinska Institute, Stockholm, Sweden
KEY WORDS: Heparinized catheter; bacterial colonization; biofilm; exit site.
H
eparin is not only an anticoagulant. It is also known to have anti-inflammatory and antimicrobial effects. Surface heparinization of central Correspondence to: Y.L. Kim, Division of Nephrology, Department of Internal Medicine, Kyungpook University Hospital, 50 Samduck-Dong, Jung-Ku, Taegu 700-721 South Korea.
[email protected]
venous catheters reduces the risk of catheter infection and bacteremia by reducing the number of microorganisms attached to the surface of the catheter (1). The aim of the present study was to evaluate whether stable surface heparinization of silicon catheters for peritoneal dialysis (PD) prevents bacterial colonization or biofilm formation, and improves healing of the exit site. MA TERIALS AND METHODS MATERIALS We performed a prospective, double-blind, randomized study. Forty male Sprague–Dawley rats with intact kidneys (250 – 300 g) were used. The rats were not omentectomized. Heparinized catheters were implanted in 20 rats (group H) and non heparinized catheters in the other 20 (group C). The 40 catheters were coded, and the codes were not revealed until the study was complete. The PD catheters, constructed of silicon tubing with two polyester cuffs, were patterned after a standard Tenckhoff catheter. Stable, permanent heparin coating of the catheters was done by Medicarb AB, Bromma, Sweden. A covalent multipoint method of attachment onto polymeric surfaces was used for chemical immobilization of the heparin. Dialysis infusions were performed twice daily for 4 weeks using a 25 mL instillation volume of 2.5% glucose solution. Prophylactic antibiotics were not used. The extent of biofilm coverage on the intraperitoneal portion of the catheter (from samples obtained at the end of the experiment) was assessed using scanning electron microscopy. Sonicated fluid from the catheter tip was cultured to evaluate the bacterial colonization of the catheter. The exit sites were evaluated at 2-week intervals using the scoring system of Pecoits–Filho et al (2). The histology of the tissues adjacent to the cuffs (from samples obtained at the S357
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We performed a prospective, double-blind, randomized study to evaluate whether stable surface heparinization of silicone peritoneal dialysis (PD) catheters prevents bacterial colonization or biofilm formation and improves healing of the exit site. Heparinized catheters were implanted in 20 Sprague–Dawley rats (group H) and non heparinized catheters in another 20 (group C). The PD catheters, constructed of silicon tubing with two polyester cuffs, were patterned after the standard Tenckhoff catheter. A covalent multipoint method of attachment onto polymeric surfaces was used for stable, permanent chemical immobilization of heparin on the PD catheter. Dialysis exchanges (25-mL instillation volume) were performed twice daily for 4 weeks through the permanent catheter. Prophylactic antibiotics were not used. The exit sites were evaluated at 2-week intervals. The extent of biofilm coverage on the intraperitoneal portion of the catheter (obtained at the end of the experiment) was assessed, and sonicated fluid from the catheter tip was cultured for evaluating bacterial colonization of the catheter. Exit-site scores in group H were lower than in group C (p = 0.052) at the end of week 4. Bacterial colonization tended to be less common in group H [2 of 12 catheters (17%)] than in group C [8 of 15 catheters (53%); p = 0.058], but the extent of biofilm, the peritonitis rate, and the inflammation score of tissue adjacent to the cuff were not different between the groups. Those data suggest that heparinized PD catheters can be a practical approach to the prevention of bacterial colonization and can improve healing of the exit site.
PROCEEDINGS OF THE IXTH CONGRESS OF THE ISPD
DECEMBER 2001 – VOL. 21, SUPPL 3
KIM et al.
end of the experiment) was evaluated using the scoring system of Fung et al (3). Their inflammation scoring system is based on a subjective evaluation of the relative degree of inflammation. RESUL TS RESULTS
DISCUSSION AND CONCLUSIONS Biofilms are defined as matrix-enclosed bacterial populations adherent to each other, to surfaces, or to interfaces (and to combinations of these) (4). Bacterial infections associated with implanted materials such as PD catheters are regarded as a major problem. The biofilm matrix seems to confer unique biologic properties on the inhabiting micro-organisms, such as enhanced resistance to host defense and to antimicrobial agents. The colonization of subcutaneous portions of PD catheters by adherent biofilm bacteria is common in
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experimental animal models of CAPD. Contiguous spread to the peritoneal part of the catheter is greatly facilitated by the dialysis procedure itself. Peritoneal infection often follows the development of bacterial colonization (5). Protection against bacterial colonization provides for better healing of exit sites for PD catheters in rats (2). Hydrophobic and electrostatic interactions play a major role in bacterial adhesion to biomaterial surfaces. The surface of a heparinized catheter is highly hydrated and reduces hydrophobic interaction with bacteria. The surface of a heparinized catheter is negatively charged, as is the bacterial cell wall. Therefore the electrical force between the heparinized catheter and the bacteria tends to repel the bacteria (6). In the present study, exit-site scores in the heparinized catheter group tended to be lower than in the control group. Bacterial colonization tended to be less common in the heparinized catheter group, but the extent of biofilm formation and the peritonitis rate were not different. Those data suggest that heparinized catheters hold promise in preventing bacterial colonization and improving healing of the exit site. Larger studies are required to substantiate our preliminary results. ACKNOWLEDGMENT This article was partly supported by a grant from the Korean Society of Nephrology (program year 2000).
REFERENCES 1. Appelgren P, Ransjo U, Bindslev L, Espersen F, Larm O. Surface heparinization of central venous catheters reduces microbial colonization in vitro and in vivo: results from a prospective, randomized trial. Crit Care Med 1996; 24(9):1482–9. 2. Pecoits–Filho RF, Twardowski ZJ, Khanna R, Kim YL, Goel S, Moore H. The effect of antibiotic prophylaxis on the healing of exit sites of peritoneal dialysis catheters in rats. Perit Dial Int 1998; 18:60–3. 3. Fung LC, Khoury AE, Vas SI, Smith C, Oreopoulos DG, Mittelman MW. Biocompatibility of silver-coated peritoneal dialysis catheter in a porcine model. Perit Dial Int 1996; 16:398–405. 4. Costerton JW, Lewandowski Z, Caldwell DE, Korber DR, Lappin–Scott HM. Microbial biofilms. Annu Rev Microbiol 1995; 49:711–45. 5. Read RR, Eberwein P, Dasgupta MK, Grant SK, Lam K, Nickel JC, et al. Peritonitis in peritoneal dialysis: bacterial colonization by biofilm spread along the catheter surface. Kidney Int 1989; 35:614–21. 6. Nomura S, Lundberg F, Stollenwerk M, Nakamura K, Ljungh A. Adhesion of staphylococci to polymers with and without immobilized heparin in cerebrospinal fluid. J Biomed Mater Res 1997; 38:35–42.
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Thirteen animals did not complete the study. Five animals died—among them, 4 that died after cardiac puncture for blood sampling (2 in group H and 2 in group C). Seven animals had catheter problems (4 in group H and 3 in group C). One animal in group H lost the external cuff immediately after catheter implantation. A total of 27 rats (12 in group H and 15 in group C) completed the 4-week study and were analyzed. Dialysate samples were collected once weekly for culture after a 4-hour dwell. Diagnosis of peritonitis was based solely on the culture results. Peritonitis was diagnosed when more than ten colonies were present. The mean peritonitis rate was not significantly different between the groups (0.44 episodes/ rat–week in group H and 0.39 episodes/rat–week in group C). The formation of biofilm was not significantly different between the groups. On the inner surface, 5 of 12 catheters in group H and 8 of 15 catheters in group C showed biofilm formation. On the outer surface, 6 of 12 catheters in group H and 8 of 15 catheters in group C showed biofilm formation. Two of 12 catheters in group H were colonized as compared with 8 of 15 catheters in group C (p = 0.058). At the end of the second week, the mean exit-site score was not significantly different between the groups (2.29 ± 1.61 in group H vs 2.67 ± 1.41 in group C). At the end of the fourth week, the mean exit-site score was 2.92 ± 1.44 in group H and 4.47 ± 2.45 in group C (p = 0.052). The mean inflammatory grade score of tissue adjacent to the cuff was not significantly different (inner cuff: 1.75 ± 1.29 in group H vs 2.53 ± 1.41 in group C; outer cuff: 2.75 ± 1.42 in group H vs 3.07 ± 0.70 in group C).
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