Cutaneous Mycobacterium shigaense Infection in Immunocompetent Woman, China

To the Editor: Mycobacterium shigaense is a novel, slow-growing, scotochromogenic mycobacterium (1), initially reported in 2012 as an opportunistic pathogen isolated from skin biopsy samples from a patient with a history of Hodgkin disease and severe cellular immunodeficiency. We describe the identification of this species in a chronic cutaneous infection in an immunocompetent woman. A 56-year-old woman was admitted to our inpatient department in August 2011 with reddish papules, nod-ules, plaques, and scars on her face and neck (Figure, panel A) that had developed over >1 year, starting in June 2010. Initially, a few small pap-ules appeared on her face; the primary papules gradually enlarged, spreading to the neck and developing into nod-ules, plaque, partly purulent lesions, and sometimes fistulas associated with moderate pain and scarring. The patient reported no history of trauma or surgical procedure and could not recall any potential inducement of the lesions or previous receipt of immuno-suppressant therapy. On physical examination, the patient was thin, with normal vital signs. Results of routine laboratory tests were unremarkable. Cephalic and cervical radiographs and computed tomography scans revealed lymph-adenectasis of the neck only; a purified protein derivative test showed an erythema ≈8 mm in diameter on the forearm. Results of testing for HIV and human T-lymphotropic virus 1 an-tibody detection tests were negative. Cell-mediated immunity levels were detected by flow cytometry of peripheral blood cells; cell counts for CD3+, CD4+, CD8+ T-cells, and T-cell receptors and for CD19+ B-cells were within reference ranges. Skin samples were collected from the face and neck of the patient and subjected to histopathologic examination , smear testing, and culture. Histopathologic examination showed a hyperplastic epidermis and nonca-seating granulomatous infiltrates of lymphocytes, histiocytes, and mul-tinucleate giant cells in the dermis (Figure, panel B). Results of Ziehl-Neelsen staining of smears for acid-fast bacilli and periodic acid–Schiff staining for fungi were negative; fungal and other bacterial cultures were sterile. Samples streaked on Löwenstein-Jensen medium at 32°C and 37°C for 4 weeks formed smooth, creamy, yolk yellow colonies (Figure, panel C); however, such colonies did not grow at 25°C and 45°C. Ziehl-Neelsen staining of samples from the colonies revealed acid-fast bacilli (Figure, panel D). Infection with a mycobacterium was suspected on the basis of these results. The isolated bacilli were subjected to PCR restriction fragment-length polymorphism analysis and sequenc-ing of the mycobacterial hsp65 gene to identify the bacteria and strain (2,3). However, a match for the restriction …