Peritoneal dialysis-related peritonitis caused by Mycobacterium iranicum: A case report and literature review

Mycobacterium iranicum is an emerging scotochromogenic, rapidly growing mycobacterium (RGM) known to cause infections in multiple organ systems. However, because only a limited number of M. iranicum infections have been reported, optimal treatments have not been established. Here, we describe the case of a man in his 80s who developed peritoneal dialysis (PD)-related peritonitis caused by M. iranicum. Dialysate cultures yielded RGM, which was subsequently identified as M. iranicum using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. After PD catheter removal, a multidrug regimen comprising amikacin, meropenem, and azithromycin was initiated. To assess inducible macrolide resistance, antimicrobial susceptibility testing with 14 days of incubation was performed, confirming macrolide susceptibility. The patient transitioned to oral azithromycin and levofloxacin and completed a 3-month course without recurrence. To our knowledge, this is the first reported case of M. iranicum PD-related peritonitis treated with an azithromycin-containing regimen. The literature review suggests that, although M. iranicum may show in vitro susceptibility to several agents used for RGM infections, the detection of the plasmid-borne erm(55) gene in M. iranicum warrants caution when interpreting macrolide susceptibility results. Macrolide susceptibility was evaluated through 14 days in this case; however, resistance genes were not assessed, and the contribution of azithromycin cannot be determined given catheter removal and other antimicrobials. In conclusion, this case illustrates that M. iranicum can cause PD-related peritonitis that may require catheter removal and individualized antimicrobial therapy. Further studies are needed to determine optimal treatment, including individual roles of agents in combination therapy, for M. iranicum infections.