Septic pulmonary emboli caused by Tsukamurella inchonensis: A case report

The genus Tsukamurella is a fastidious, environmental organism that potentially causes various infections in humans. Due to the morphological and biochemical similarities to others pathogens, such as Gordona, Rhodococcus, Corynebacterium, Nocardia, and Mycobacterium, a molecular-based approach is indispensable to correctly identify them. Herein, we describe a case of Tsukamurella inchonensis bacteremia complicated with septic pulmonary emboli (SPE), which is the first in the literature. A 44-year-old Japanese woman diagnosed with tongue cancer had undergone partial tongue resection. While receiving chemotherapy and radiotherapy, she developed high fever. Chest computed tomography suggested multiple emboli at the bilateral, peripheral lungs, indicating SPE. Blood culture detected Gram-positive rods, to which matrix-assisted laser desorption/ionization-time of flight mass spectrometry failed to identify. Then, we attempted to characterize it by 16S rRNA sequence, which suggested the organism to be Tsukamurella species but resulted in low resonance of the species-level identification. Additionally, we employed a confidence gene targeting groEL, leading to 100% matching (753/753 bps) with T. inchonensis NCTC 10741 (GenBank accession no. LR131273.1), which has been incorrectly registered as wrong species name Tsukamurella paurometabola in the database. Under the diagnosis of T. inchonensis-associated SPE, we successfully treated the patient with imipenem/cilastatin administration for 4 weeks. Sequencing analysis of groEL was of great use in identifying the organism in this case. More clinical cases based on molecular diagnosis of the fastidious pathogens need to be accumulated to further understand the characteristics and appropriate treatment regimen.