[A. xylosoxidans and R. radiobacter-Induced Polimicrobic Peritonitis in Peritoneal Dialysis: A Case Report].

Rhizobium radiobacter and Achromobacter xylosoxidans are two Gram-negative microorganisms found in soil. They are only rarely pathogenic to humans. There have been few cases reported of human infections, and even fewer cases of peritonitis in peritoneal dialysis. However, there is a higher risk in immunocompromised individuals. These microorganisms have the ability to form biofilms, leading to catheter-related infections, and possess intrinsic antibiotic resistance properties that are not well understood, making it challenging to identify specific therapies. We present a clinical case of a 61-year-old man undergoing automated peritoneal dialysis (APD) for end-stage renal disease due to light chain deposition disease in multiple myeloma. He was admitted to our department just over a month after starting replacement therapy due to a positive combur test and turbid fluid. The subsequent diagnosis was polymicrobial peritonitis caused by R. radiobacter and A. xylosoxidans. Despite initial empirical intraperitoneal antibiotic therapy with cefazolin and tobramycin, the treatment was optimized by introducing cefepime both intravenously and intraperitoneally, but without significant improvement. Given the diagnosis of refractory polymicrobial peritonitis, removal of the peritoneal catheter was necessary, resulting in drop-out from peritoneal dialysis. Although the outcome was unfavorable for the dialytic method, the purpose of our case report is to describe the first Italian case of peritonitis in peritoneal dialysis caused by these atypical pathogens in an immunocompromised patient. We hope this information will assist clinicians in their practice, as the available literature helped us in our diagnostic and therapeutic approach for this patient.