Peritoneal dialysis-associated peritonitis caused by Ureaplasma urealyticum

Rationale: Ureaplasma urealyticum is a rare cause of peritoneal dialysis-associated peritonitis (PDAP) that may be missed by routine culture. Here, we report a culture-negative case in which targeted next-generation sequencing (tNGS) supported rapid pathogen identification and treatment adjustment. Patient concerns: A 41-year-old woman receiving continuous ambulatory peritoneal dialysis for >10 years presented with acute abdominal pain, cloudy dialysate, fever, and neutrophilic dialysate leukocytosis. The patient was diagnosed with PDAP. Diagnoses: Repeated bacterial and fungal cultures and acid-fast staining were negative. tNGS of peritoneal dialysate detected U urealyticum , which is considered the most likely causative pathogen. Interventions: Empirical vancomycin plus ceftazidime, followed by vancomycin plus meropenem, was ineffective. The treatment was changed to oral doxycycline plus intraperitoneal levofloxacin after the tNGS results became available. A vaginal U urealyticum isolate was subsequently resistant to levofloxacin; therefore, levofloxacin was replaced with intravenous azithromycin. Outcomes: The abdominal pain resolved, the dialysate cleared, inflammatory markers decreased, the PD catheter was retained, and no recurrence occurred during the 1-month follow-up period. Lessons: In persistent culture-negative PDAP that does not respond to cell wall-active antibiotics, clinicians should consider cell wall-deficient organisms such as Ureaplasma . tNGS may complement conventional microbiological testing, but the results should be interpreted in the clinical context and, when possible, confirmed by an independent method.