Case Report: Mycobacterium abscessus knee joint infection following herbal steam bath: successful short-course oral therapy in an immunocompetent patient.

BACKGROUND: The Mycobacterium abscessus complex (MABC), a multidrug-resistant environmental mycobacterium, rarely causes joint infections, which typically involve prosthetic joints. We describe the first case of native-knee M. abscessus infection linked to herbal steam therapy and osteoarthritis-a previously unreported scenario, accompanied by a literature review of 20 global MABC joint infection cases (2013-2024). Our findings present an alternative approach to the therapeutic guidelines for nontuberculous mycobacteria (NTM) infections, demonstrating successful clinical resolution in this single case using a short-course oral regimen.

CASE REPORT: A 54-year-old immunocompetent male with chronic knee osteoarthritis and a 6-year history of knee pain developed acute septic arthritis after knee-level high-temperature herbal steam baths. M. abscessus subsp. abscessus was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and hsp65 gene sequencing. Despite premature discontinuation of therapy, a 3-month oral regimen of clarithromycin (1,000 mg/day) combined with linezolid (600 mg/day) achieved full functional recovery, evidenced by a daily walking capacity of 8,000 steps.

CONCLUSION: Review of 20 MABC joint infection cases from the literature revealed the knee as the most frequently affected site (55%), with the majority of patients (95%) having a history of joint surgery. This case highlights: 1) Herbal steam therapy, degenerative joint disease, and prior interventions as underrecognized risk factors; 2) Rapid molecular diagnostics (MALDI-TOF MS/hsp65) critical for early diagnosis; 3) Short-course oral therapy (clarithromycin/linezolid) as a potential option for localized infection when prolonged therapy is impractical.