Peritoneal dialysis-related peritonitis caused by Mycobacterium iranicum: A case report and literature review.
Hirotaka Yamashita, Daisuke Ono, Kazuyuki Mimura et al.
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Case in brief
A man in his 80s developed peritoneal dialysis-related peritonitis. Dialysate cultures grew a rapidly growing mycobacterium, identified as Mycobacterium iranicum by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The PD catheter was removed, and amikacin, meropenem, and azithromycin were started. Susceptibility testing after 14 days of incubation showed macrolide susceptibility; resistance genes were not assessed. He transitioned to oral azithromycin and levofloxacin, completed a 3-month course, and had no recurrence. The contribution of azithromycin cannot be separated from catheter removal and the other antimicrobials.
What made this case unusual
The report describes M. iranicum as the cause of PD-related peritonitis and use of an azithromycin-containing regimen. Interpretation of macrolide susceptibility is complicated by the reported erm(55) resistance gene; this patient's resistance genes were not assessed.
Diagnostic / clinical pearl
When a rapidly growing mycobacterium is isolated from dialysate, species-level identification can establish M. iranicum. Interpret macrolide susceptibility cautiously, considering inducible resistance and erm(55); this case's testing showed susceptibility after 14 days, but resistance genes were not assessed.
Why it matters
Optimal treatment for M. iranicum infections is not established. This case cannot determine azithromycin's individual contribution because catheter removal and other antimicrobials were also used.