First Isolation of Mycobacterium virginiense From a Human Pulmonary Specimen

Dear Editor, Mycobacterium virginiense is a recently described species of the Mycobacterium terrae complex (MTC) [1, 2]. It is recognized as an infectious agent of clinical importance [3]. M. virginiense is a slow-growing nontuberculous mycobacterium (NTM) that was first identified in 2016 along with three other validated clinical strains causing tenosynovitis and osteomyelitis [1]. The three M. virginiense isolates were nonchromogenic on Middlebrook 7H10 agar (Sigma-Aldrich, St. Louis, MO, USA) and were resistant to several antibiotics, including rifampin and quinolones. M. virginiense had never been isolated from the human body until Vasireddy, et al. [1, 2] reported three isolates from the tendon, elbow, and knee. Since the first report in 2016, only two more M. virginiense isolates, one from a mud specimen of a swine farm in Japan [4] and another from bovine fecal specimens [5], have been reported. We report the first isolation of M. virginiense from a human pulmonary specimen. This study was approved by the Institutional Review Board of Samsung Medical Center, Seoul, Korea (No. 2019-05-117), which waived the need for informed consent from the patient. A 67-year-old male patient visited the pulmonary department every year at Samsung Medical Center because of NTM infection. He had a history of tuberculous pleurisy at age 21 and had been diagnosed as having NTM pulmonary disease caused by Mycobacterium massiliense at age 54. He had been treated for two yrs with an antibiotic regimen that included clarithromycin and ciprofloxacin until his sputum culture showed negative results. He had been diagnosed as having chronic pulmonary aspergillosis at age 62. The patient submitted sputum specimens every year for acid-fast bacilli staining and culture testing. NTM has been repeatedly isolated from three yearly consecutive sputum specimens since the age of 65. Sputum cultures were performed using liquid media with Middlebrook 7H9 broth in an MGIT 960 system (Becton Dickinson, Sparks, MD, USA) and using solid media with 3% Ogawa agar (Shinyang, Seoul, Korea). A line probe assay for the internal transcribed spacer gene (AdvanSure Mycobacteria GenoBlot Assay; LG Chem, Seoul, Korea) revealed that all three isolates were unidentifiable Mycobacterium species. For definitive species identification, 16S rDNA and rpoB genes from two out of three isolates were sequenced according to the protocol outlined in the Clinical and Laboratory Standards Institute (CLSI) guidelines MM18-A [6]. Using the basic local alignment search tool (BLAST) algorithm, we found that the 16S rDNA and rpoB sequences exhibited 100% (518/518 bp) and 99.4% (340/342 bp) similarity, respectively, to those of M. virginiense. The next