MALDI-TOF mass spectrometry-based identification of Mycobacterium wolinskyi in peritoneal dialysis-associated peritonitis: a case report

Abstract Background Peritonitis is a major complication of peritoneal dialysis (PD). Early identification of the causative organism is critical for selecting appropriate antimicrobial therapy in PD-associated peritonitis. However, species-level identification can be challenging when the infection is caused by an uncommon pathogen. Case presentation We report a case of an 84-year-old man undergoing PD who developed peritonitis with concomitant exit-site infection. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) identified the organism as Mycobacterium wolinskyi , a rare rapidly growing mycobacterium, enabling prompt modification of antimicrobial therapy to a targeted regimen. After 6 weeks of antimicrobial therapy and PD catheter exit-site relocation, the patient showed clinical improvement and was discharged. At 1 month later, however, peritonitis due to M. wolinskyi recurred, necessitating removal of the PD catheter. Conclusions This case suggests that MALDI-TOF MS may facilitate timely species-level identification and help to determine initial antimicrobials for the causative organism in PD-associated peritonitis.