A Case of Peritoneal Dialysis-Related Peritonitis Due to Moraxella osloensis.

A 46-year-old woman on peritoneal dialysis (PD) had cloudy peritoneal dialysis effluent that had persisted for 10 days by the time she visited our hospital. The white blood cell count in the effluent was elevated to 1500/μL, leading to a diagnosis of peritoneal dialysis-associated peritonitis. The effluent cleared within two days with treatment using cefazolin and ceftazidime, and the white blood cell count dropped to 0/μL by day 6. Culture of the effluent revealed the presence of Moraxella osloensis. The patient's treatment was switched to ceftazidime monotherapy, and antibiotic therapy for 21 days resulted in the resolution of the peritonitis. Reports of peritonitis caused by Moraxella osloensis are rare; however, with the spread of diagnostic methods, such as matrix-assisted laser desorption ionization-time of flight mass spectrometry, an increase in reported cases is expected. Unlike previous cases, in this case, the interval from onset to treatment initiation was longer. However, similar to reported cases, in this case, the infection was cured with antibiotic treatment without the need for PD catheter removal.