Since the introduction of continuous ambulatory peritoneal dialysis (CAPD) by Popovish in 1976, peritoneal dialysis has been an important treatment for end stage renal disease (ESRD) [1]. Although its frequency in CAPD patients has been decreasing, peritonitis is still a major cause of morbidity and mortality in patients [1].

Achromobacter xylosoxidans is a gram-negative bacillus. The nomenclature originated from bacteria that produce alkaline (Achromobacter) and acid components from xylose using oxidation (xylosoxidans) [2]. The three species Achromobacter faecalis, Achromobacter piechaudii, and Achromobacter xylosoxidans exhibit these biochemical characteristics [3]. Among these, only Achromobacter xylosoxidans has been identified as a causative agent of CAPD peritonitis. This species is a rare pathogen of peritonitis. CAPD peritonitis caused by Achromobacter xylosoxidans has been treated by antibiotics with antipseudomonal effects after catheter removal [1-5]. However, it has high morbidity and recurrence rate because of its virulence and antimicrobial resistance [4].

Identification of Achromobacter xylosoxidans in peritoneal dialysate was first reported in 1980 [5], and since then there have been nine reported cases of CAPD peritonitis caused by Achromobacter xylosoxidans [1-8]. However, there is limited knowledge about the clinical characteristics, prognosis, or proper treatments of this fatal disease. We recently experienced one case of peritonitis by Achromobacter xylosoxidans and hereby report the case along with a comprehensive review of reported cases. To the best of our knowledge, this is the first comprehensive report of CAPD peritonitis caused by Achromobacter xylosoxidans in Korea.

A 74-year-old female with an 18-year history of diabetes, 13 years of high blood pressure, four years of ESRD and regular CAPD treatment, and a five-month history of recurrent peritonitis was diagnosed with peritonitis with turbid peritoneal dialysate for two weeks before presentation. Vancomycin and amikacin were empirically injected via peritoneal dialysate for seven days, but the leukocyte count of the peritoneal dialysate increased. Achromobacter xylosoxidans was identified in the peritoneal dialysate following cultivation examination. The strain was sensitive to ceftazidime, imipenem, meropenem, levofloxacin, and piperacillin, which led the patient's antibiotics to be changed to imipenem/cilastatin and piperacillin/tazobactam via peritoneal dialysate for another seven days. However, the patient showed mental changes and was transferred to our hospital via the emergency room.

At the time of arrival, she was diagnosed with peritonitis and septic shock and was moved to the intensive care unit. Her examination results showed a total leukocyte count in the peripheral blood of 21,330/µL (neutrophil 93.4%, lymphocyte 2.8%, monocyte 3.0%, eosinophil 0.2%, basophil 0.3%), and a platelet count of 289,000/µL. The leukocyte count of the peritoneal dialysate was 650/µL (82% polymorphonuclear cells, 18% mononuclear cells). At the day of arrival, ceftazidime and cefazolin were injected via peritoneal dialysate, and imipenem/cilastatin and vancomycin were empirically injected through a vein. On the third day after arrival, the leukocyte count in the peritoneal dialysate decreased to 310/µL (94% polymorphonuclear cells, 6% mononuclear cells), and the patient's vital signs were stabilized. Pseudomonas aeruginosa, which was sensitive to imipenem, meropenem and piperacillin, was identified in the cultivation examination of the peritoneal dialysate performed on the first hospital day; imipenem/cilastatin and vancomycin were maintained. On the fourth day after arrival, the patient had a fever and experienced mental changes, and the peritoneal dialysate became turbid again. Bowel perforation was excluded by simple abdomen and chest x-ray imaging. Laboratory tests were performed, showing a leukocyte count of 1,320/µL in the peritoneal dialysate (95% polymorphonuclear cells, 5% mononuclear cells). Another cultivation examination of the peritoneal dialysate identified Achromobacter xylosoxidans, which had the same sensitivity to antibiotics as the previous pathogen.

Since the peritonitis was not improved, the CAPD catheter was removed on the fifth day after admission. On the cultivation examination of the catheter, Achromobacter xylosoxidans and Pseudomonas aeruginosa were identified. According to antibiotics sensitivity, intravenous imipenem/cilastatin was maintained and vancomycin was empirically used every fourth day. CAPD was changed to hemodialysis three to four times a week. On the 25th hospital day, aspiration pneumonia and cellulitis on the right arm occurred. Even after antibiotic treatment and ventilator care, the aspiration pneumonia worsened, and the patient died on the 34th day of hospitalization.

CAPD peritonitis is caused mainly by aerobic gram-positive cocci (Staphylococcus epidermidis, Staphylococcus aureus) or gram-negative bacilli (Escherichia coli, Pseudomonas aeruginosa), although anaerobes, fungi and mycobacteria have been identified in rare cases [1]. Up to 30% of cultivation examinations cannot identify a causative organism [1]. Generally, bacterial CAPD peritonitis is treated by an antimicrobial injection into the abdominal cavity and eliminated by intravenous antimicrobial treatments. However, peritonitis caused by gram-negative bacilli such as Pseudomonas aeruginosa requires CAPD catheter removal [3].

Achromobacter xylosoxidans was first reported by Yabuucho in 1971, identified from the suppurative exudates of seven patients with chronic otitis media [2]. Achromobacter xylosoxidans can be isolated from many clinical samples [1], but its frequency is rare, and this case is the first report of CAPD peritonitis caused by Achromobacter xylosoxidans in Korea. This species is an aerobic bacterium and a gram-negative bacillus, showing positive oxidase and catalase results [1]. This species is an organism of normal flora that can be identified from the alimentary canal or the skin of normal human bodies, and can be identified in underwater environments as well [3]. As a pathogen, this species is more frequently identified in patients with immune deficiencies such as HIV (human immunodeficiency virus) infection or neutropenia. ESRD patients are another immune-deficient group, and the peritoneal dialysate itself offers a suitable aquatic environment for this strain [2]. The species has been reported to cause meningitis, eye infections, endocarditis, otitis media, respiratory infections, osteomyelitis and bacteremia, in addition to peritoneal dialysate infection. The treatment and prognosis are not clear due to the rarity of cases [2].

There have been ten reported cases of CAPD peritonitis by Achromobacter xylosoxidans, including the one presented in this paper. We summarized the clinical characteristics of those cases in Table 1 and 2. Patient ages ranged from 16 to 76 years (mean age: 46.9), and the sex ratio was 4:6 (male:female). The underlying diseases included four cases of diabetes mellitus (DM), two cases of hypertension and Ig A nephropathy, one case of acute renal failure, and one case of idiopathic Fanconi syndrome. Co-infected pathogens were isolated in three patients, two of whom died. The first reported case of CAPD peritonitis caused by Achromobacter xylosoxidans was reported by Ingra and Siegman in 1980. Achromobacter xylosoxidans and Staphylococcus epidermidis were simultaneously identified with the cultivation examination of peritoneal dialysate, and the patient was completely cured with the use of parenteral carbenicillin [5]. However, in another report in which there were co-infections with Stenotrophomonas maltophilia, treatment failed [6]. Identification of only Achromobacter xylosoxidans was found in seven cases. One of seven cases was reported in 1986 by Morrison and Boyce. They initially used tobramycin and cephalothin, but the antimicrobials had no effect. The patient was cured with trimethoprim-sulfamethoxazole [2]. The rest of them resulted in treatment failure [7].

Achromobacter xylosoxidans is a rare cause of CAPD peritonitis with a high treatment failure rate. Because of its virulence and antimicrobial resistance, many experts recommend early catheter removal if patient condition does not improve [3]. Unfortunately, we cannot establish a standard antibiotic regimen or antimicrobial resistance pattern because there are only a few reported cases. We report one case of CAPD peritonitis caused by Achromobacter xylosoxidans , with a literature review. Further studies are necessary to identify the clinical characteristics, prognosis, and proper treatment of this disease.