Xanthomonas maltophUia Peritonitis in Uremic Patients Receiving Continuous Ambulatory Peritoneal Dialysis C.C. Szeto, MB ChB, MRCP, Philip K.T. Li, MBBS, FRCPE, FACP, C.B. Leung, MB ChB, MRCP, Alex W.Y. Yu, MBBS, FACP, S.F. Lui, MBBS, FRCPE, and K.N. Lai, MD, DSc, FRCP • Xanthomonas maltophilia peritonitis has been only occasionally reported in patients receiving continuous ambu- latory peritoneal dialysis. We present a series of six cases of peritonitis caused by such bacteria, accounting for 1.5% of all peritonitis episodes encountered in our renal unit over the past 5 years. Recent bacterial peritonitis treated with broad-spectrum antibiotics was the major risk factor, and the outcome was poor with medical treatment alone. Secondary peritonitis, especially fungal, was common and probably related to the prolonged course of antibiotics. All patients eventually required removal of the catheter, either because the effluent failed to clear up or because of secondary peritonitis. We suggest that X maltophilia peritonitis be treated with double antibiotics as soon as it is diagnosed. To prevent the development of superimposed infection after prolonged administration of antibiotics, the Tenckhoff catheter should be removed if the peritonitis fails to respond to a short course of antibiotics. © 1997 by the National Kidney Foundation, Inc. INDEX WORDS: Peritoneal dialysis; peritonitis; Xanthomonas maltophilia. T HE ORGANISM Xanthomonas maltophi- lia, previously identified as Pseudomonas maltophilia, is a common environmental sapro- phyte. Clinical reports of opportunistic infection by this organism were rarely reported before the 1980s because it was not distinguished from other non-Pseudomonas aeruginosa organisms. However, over the past few years, X maltophilia has been increasingly recognized as an emerging nosocomial pathogen) Increasing use of broad- spectrum antibiotics, especially the carbapenems, as well as contamination of water supplies proba- bly also contribute to the increased incidence. Infections presenting as septicemia, meningitis, and endocarditis have been reported. 2'3 X mal- tophilia peritonitis related to the treatment of continuous ambulatory peritoneal dialysis (CAPD) has been occasionally reported. 4 We present our experience over the past 5 years of six patients with X maltophilia peritonitis com- plicating CAPD. SUBJECTS AND METHODS Data were collected regarding all peritonitis episodes in patients receiving CAPD in our unit from 1990 to 1994. Peritonitis was diagnosed with the usual clinical triad of ab- dominal pain, fever, and cloudy peritoneal effluent. Episodes with peritoneal eosinophilia but negative bacterial culture were excluded. Dialysate effluent was sent for culture in BACTEC NR6A bottles (Becton Dickinson, Sparks, MD). During the 5-year study period, 392 episodes of peritonitis were recorded; six were due to X maltophilia. The case records of these six patients were analyzed. The patient characteristics, underlying medical conditions, set- tings of CAPD, living environment, baseline biochemical data, previous peritonitis, and recent antibiotic usage were reviewed. The antibiotic regimens used to treat the X mal- tophiIia peritonitis in individual patients were studied. In our unit, as soon as the peritonitis was diagnosed, all patients received intraperitoneal vancomycin and imipenem for 10 days as first-line therapy while culture results were pending. Subsequent antibiotic therapy depended on the sensitivity of responsible bacteria and the clinical response of the patient. Removal of the Tenckhoff catheter was considered when the effluent failed to clear with antibiotics alone. All six of our patients were followed for at least 6 months after the treat- ment was completed, and their outcome was assessed. RESULTS During the 5-year study period, 392 episodes of peritonitis were recorded. The incidence of peritonitis in our unit was one episode per patient per 35 months. The microbial histogram is simi- lar to the rest of the world, with approximately 50% staphylococcus and 20% gram-negative ba- cilli. Six patients with X maltophilia peritonitis were recorded, which accounted for 1.5% of all From the Department of Medicine, Prince of Wales Hospi- tal, Chinese University of Hong Kong, Shatin, Hong Kong. Received January 31, 1996; accepted in revisedform Au- gust 20, 1996. Supported by the Thomas and Rim Research Fund (Hong Kong). Address reprint requests to Philip K.T. Li, MBBS, FRCPE, FACP, Department of Medicine, Prince of Wales Hospital, Shatin, Hong Kong. © 1997 by the National Kidney Foundation, Inc. 0272-6386/97/2901-0011$3.00/0 American Journal of Kidney Diseases, Vol 29, No 1 (January), 1997: pp 91-95 91