Prevention of peritonitis in continuous ambulatory peritoneal dialysis

A case of peritonitis caused by Roseomonas gilardii in a patient undergoing continuous ambulatory peritoneal dialysis

A case of peritonitis caused by Roseomonas gilardii in a patient receiving continuous ambulatory peritoneal dialysis is presented. The patient's domestic water supply was implicated as the probable source of infection. This is the first report of R. gilardii causing such an infection.

Host defences in continuous ambulatory peritoneal dialysis and the genesis of peritonitis

Continuous ambulatory peritoneal dialysis (CAPD) has come to be extensively used for the treatment of end-stage renal failure in children, and especially infants, such that now more than half of children on dialysis worldwide receive treatment by this means. Peritonitis, however, is commoner in children than in adults receiving treatment, and is a major source of morbidity and treatment failure in children started on CAPD. Only recently has the immunology of the normal peritoneum been studied extensively, with the need to assess the impact of the installation of large volumes of fluid into the peritoneal sac during dialysis. The main phagocytic defences of the peritoneum depend upon a unique set of macrophages which are present free in the peritoneal fluid but also in the submesothelium and in perivascular collections together with B lymphocytes in the submesothelial area. Both the number of macrophages per unit volume and the concentration of opsonic proteins, such as IgG, complement and fibronectin, are reduced to between only 1% and 5% when dialysis fluid is continuously present in the peritoneal sac. In addition, the fluids used for CAPD are toxic to both macrophages and to mesothelial cells. Thus minor degrees of contamination frequently lead to peritonitis and in addition the majority of patients have catheters inserted in their peritoneum which become colonised with organisms capable of producing exopolysaccharide (slime), which promotes adhesion of the organism to the plastic and protects them against phagocytic attack and the penetration of antibiotics. Thus the peritoneum is in a state of continual inflammation, as well as being a markedly more vulnerable site than the normal peritoneum to the entry of organisms. Whether clinical peritonitis appears in this state of chronic contamination probably depends on perturbation in the balance between host defences and the organism. Whilst Staphylococcus epidermidis is the commonest cause of peritonitis, Staphylococcus aureus and Gram-negative organisms are much more serious and more frequently lead either to temporary catheter removal or discontinuation of dialysis altogether. This review describes the peritoneal defences in relation to the genesis of peritonitis.

Audit of infection in continuous ambulatory peritoneal dialysis

The major cause of failure of continuous ambulatory peritoneal dialysis is peritoneal or exit site infection with Staphylococcus aureus. From 1989-1992, eradication of nasal and perineal carriage, continued use of an occlusive dressing to the exit site, improved aseptic technique for dressing changes by the patient and avoidance of wetting of the dressing were used in an attempt to reduce staphylococcal infections. By comparison with the 3-year period prior to intervention, a significant increase in the life of the catheters was achieved (removed at 1 year, 13 vs. 28%, P < 0.001) with a reduction in episodes of peritonitis due to S. aureus. The study was not prospectively controlled but there did not appear to be any other factor to account for the sudden and consistent improvement observed.

Controlled trial of a Y-set dialysis delivery system to prevent peritonitis in patients receiving continuous ambulatory peritoneal dialysis

Peritonitis rates were compared in patients receiving continuous ambulatory peritoneal dialysis (CAPD) via either a Y-set dialysate delivery system or a standard system. Forty patients in each arm of the trial were matched for age (range 20-67 years, mean 49 years), and remained in the study for similar periods (range 3-36 months, mean 14.1 months). The observation time was 564 patient-months for each arm of the trial. There were 22 episodes of peritonitis in nine out of 40 patients using the Y-set and 57 episodes in 21 out of 40 patients using the standard system (P = 0.005 Wilcoxon signed rank test for episodes, P = 0.02 McNemar's chi 2 test for patients). Peritonitis rates were one episode per 25 patient-months in the Y-set group, and one episode per 9.7 patient-months in the standard group. In the Y-set group there were significantly fewer episodes caused by coagulase-negative staphylococci and Acinetobacter spp. There was no difference in the rate of episodes caused by Staphylococcus aureus, streptococci, enterococci, corynebacteria, enterobacteria or pseudomonads. There was no difference in the incidence of catheter exit wound infections. The Y-set dialysis delivery system is effective in reducing peritonitis rates in CAPD patients caused by organisms derived from the commensal skin flora, principally coagulase-negative staphylococci, but does not reduce peritonitis caused by other organisms.

Microbiological aspects of peritonitis associated with continuous ambulatory peritoneal dialysis

The process of continuous ambulatory peritoneal dialysis has provided a useful, relatively inexpensive, and safe alternative for patients with end-stage renal disease. Infectious peritonitis, however, has limited a more widespread acceptance of this technique. The definition of peritonitis in this patient population is not universally accepted and does not always include the laboratory support of a positive culture (or Gram stain). In part, the omission of clinical microbiological findings stems from the lack of sensitivity of earlier microbiological efforts. Peritonitis results from decreased host phagocytic efficiency with depressed phagocytosis and bactericidal capacity of peritoneal macrophages. During episodes of peritonitis, fluid movement is reversed, away from the lymphatics and peritoneal membrane and toward the cavity. As a result, bloodstream infections are rare. Most peritonitis episodes are caused by bacteria. Coagulase-negative staphylococci are the most frequently isolated organisms, usually originating from the skin flora, but a wide array of microbial species have been documented as agents of peritonitis. Clinical microbiology laboratories need to be cognizant of the diverse agents so that appropriate primary media can be used. The quantity of dialysate fluid that is prepared for culture is critical and should constitute at least 10 ml. The sensitivity of the cultural approach depends on the volume of dialysate, its pretreatment (lysis or centrifugation), the media used, and the mode of incubation. The low concentration of microorganisms in dialysate fluids accounts for negative Gram stain results. Prevention of infection in continuous ambulatory peritoneal dialysis patients is associated with the socioeconomic status of the patient, advances in equipment (catheter) technology, and, probably least important, the application of prophylactic antimicrobial agents.

Infectious consequences of continuous ambulatory peritoneal dialysis

The peritoneal cavity of patients undergoing CAPD is critically immunocompromised and infectious peritonitis is the most important complication of the technique. Nevertheless, recent research into the epidemiology and pathogenesis of infections caused by the most important microorganisms has enabled significant reductions in peritonitis rates to be made. Peritonitis caused by Staphylococcus aureus and Pseudomonas aeruginosa can be prevented by eliminating their principal source, an infected Tenckhoff catheter wound. The source of infection for coagulase-negative staphylococci and other pseudomonads cannot be eliminated, but peritonitis caused by these organisms may be prevented by interrupting their routes of entry into the peritoneal cavity. The identification of host factors predictive of enhanced susceptibility to infectious peritonitis offers the further possibility of prevention by immunological approaches. Although the main difficulties surrounding the diagnosis of infective peritonitis have been clarified, approximately 20% of episodes remain culture-negative, with multifactorial aetiology. Initial (empirical) combination antibiotic therapy can be both appropriate and effective in approximately 85% of cases. Intraperitoneal monotherapy with fluoroquinolones has been equally successful, and these agents may prove effective by the oral route, offering considerable advantages in cost and convenience. Approximately 5% of episodes of bacterial peritonitis are unresponsive to antibiotic therapy. These cases may be conveniently managed by the technique of Tenckhoff catheter removal and replacement at a single operation.