First Report of Tenosynovitis Caused by Mycobacterium virginiense in Korea

Abstract

Dear Editor, Mycobacterium terrae complex (MTC) are slow-growing nontuberculous mycobacteria (NTM) that cause tenosynovitis, septic arthritis, and osteomyelitis of the extremities [1]. Eleven new species of MTC have been described since 2006 [2]. Mycobacterium virginiense, a member of the MTC, was first described in 2016, and isolates from patients with tenosynovitis and osteomyelitis are acid-fast, slow-growing, and nonpigmented on Middle brook 7H10 agar [2]. The first case of M. virginiense isolated from a human pulmonary specimen was reported in 2019 [3]. We report the first case of tenosynovitis caused by M. virginiense in Korea. This retrospective study was approved by the Institutional Review Board of Jeju National University Hospital, Jeju, Korea (No. 2019-07-018) that waived informed consent.A previously healthy 68-year-old woman was admitted to Jeju National University Hospital with painful swelling of the third finger of her left hand, which had been present for one month; her hand was treated with acupuncture two months before admission. She had a leukocyte count of 5.70 (reference range: 4.5-11.0) × 10 9 /L, an erythrocyte sedimentation rate of 41 (reference range: 0-20) mm/hr, and C reactive protein levels of 2.10 (reference range: 0.76-28.5) nmol/L. Magnetic resonance imaging of her left hand revealed an effusion, synovial proliferation of the flexor tendon sheath, and subcutaneous fat edema of the third finger ( Fig. 1). She was treated empirically with cefazolin and clindamycin for three weeks following which she underwent surgical debridement. Tenosynovitis and severe inflammatory changes of the soft tissue surrounding the flexor tendon were observed during surgery. Bacterial culture, acid-fast bacilli (AFB) stain, and tuberculosis (TB)-PCR were negative in the tissue specimen of the inflammatory soft tissue surrounding the tendon. On day 22, an AFB culture performed at the Korean Institute of Tuberculosis revealed an unidentified NTM. Cefazolin and clindamycin were discontinued, and oral clarithromycin (500 mg twice a day) and intravenous amikacin (10 mg/kg/day) and cefoxitin (12 g/day) were started, based on a presumptive diagnosis of rapid-growing NTM infection. Two weeks later, the regimen was changed to oral clarithromycin and ciprofloxacin (500 mg twice a day). The patient improved clinically and was discharged on hospital day 40.Molecular methods, including rpoB gene PCR, were used for definitive species identification, and slow-growing M. virginiense was confirmed with an accuracy of 99% (341/343 bp) using the basic local alignment search tool algorithm (Fig. 2) [4]. The rpoB