Expired Dialysate, Unexpected Pathogen

Peritoneal dialysis (PD)–associated peritonitis is most commonly caused by skin or enteric organisms, while environmental actinomycetes are rarely implicated. Streptomyces species are ubiquitous soil bacteria but are exceedingly uncommon human pathogens, with no prior reports of PD-associated peritonitis confirmed by molecular methods. We report a case of Streptomyces olivaceus peritonitis in a 43-year-old man receiving automated PD for 7 months, who presented with abdominal pain and cloudy effluent following use of an expired dialysate bag. Initial Gram stain revealed filamentous Gram-positive bacilli, but routine cultures were negative, and Matrix-Assisted Laser Desorption/Ionization–Time of Flight mass spectrometry misidentified the organism. Due to persistent symptoms, the PD catheter was removed, and subsequent culture demonstrated dry, wrinkled, chalky colonies. Definitive identification was achieved by 16S rRNA gene sequencing, showing 100% identity with S. olivaceus . The patient was treated with prolonged antimicrobial therapy and achieved complete clinical recovery. Post hoc inspection of expired dialysate revealed visible defects and polymicrobial contamination, supporting a plausible environmental source. This case highlights key diagnostic challenges in atypical peritonitis, including limitations of conventional microbiologic methods and the critical role of molecular diagnostics. It also underscores the potential risk associated with expired PD supplies, particularly in decentralized or resource-limited settings, and supports the need for enhanced patient-level inspection and supply chain safeguards to prevent similar events.