Mycobacterium arupense in Cancer Patients: An Emerging Infection or a Commensal Organism

Vertebral Osteomyelitis Caused by Mycobacterium arupense Mimicking Tuberculous Spondylitis: First Reported Case and Literature Review

Mycobacterium arupense is a slow-growing, nontuberculous mycobacterium widely found in the environment and is known to cause tenosynovitis and osteomyelitis, mainly in the hands and wrists. We present the first case of vertebral osteomyelitis caused by M arupense in a 78-year-old man with renal cell carcinoma. The patient had a history of tuberculous pleuritis in childhood. Although the nucleic acid amplification test of the vertebral tissue for Mycobacterium tuberculosis was negative, we initiated tuberculosis treatment based on the history and pathological findings of auramine-rhodamine-positive organisms and epithelioid cell granulomas. Subsequently, the isolated mycobacterium was identified as M arupense by genome sequencing. Accordingly, the treatment regimen was changed to a combination of clarithromycin, ethambutol, and rifabutin. Owing to a subsequent adverse event, rifabutin was switched to faropenem, and the patient was treated for a total of 1 year. In previous literature, we found 15 reported cases of bone and soft tissue infections caused by M arupense, but none of them had vertebral lesions. Physicians should be aware that M arupense can cause vertebral osteomyelitis mimicking tuberculous spondylitis. In addition, molecular testing of isolated mycobacteria is essential for diagnosis, even if tuberculous spondylitis is suspected.

The case report of Mycobacterium arupense wound infection in diabetes mellitus patients; the first report and literature review

Mycobacterium arupense is among the opportunist pathogens of atypical mycobacteria emergence (atypical mycobacteria) that is one of the isolated and reported environmental and clinical specimens. Numerous cases of osteo-articular infections of this bacterium are reported nowadays, while the pulmonary infection is rare. We identified Mycobacterium arupense in non-healing wound infection of an elderly woman with history of diabetes mellitus. She has negative tests for HIV, HBV and HCV, but was positive for HTLV-1. The patient was referred according to mild-fever, non-healing, destructive, and swelled lesion on her left foot. The mycobacterial wounds infection was suspected due to her non-conclusive previous treatment. The pathology, acid-fast staining, conventional and 16S rRNA sequencing confirmed the micro-organism to be M. arupense. Finally, the patient recovered following two-week consumption of clarithromycin, ethambutol and rifabutin. The results of this study provide evidence on the potential pathogenicity, clinical outcomes and treatment of infections caused by this bacterium.

Isolation of Mycobacterium arupense from pleural effusion: culprit or not?

BACKGROUND

Mycobacterium arupense, first identified in 2006, is a slow-growing nontuberculous mycobacterium (NTM) and an emerging cause of tenosynovitis, potentially associated with immunosuppression. However, unlike the diagnostic value of its isolation from osteoarticular specimens, the significance of detecting M. arupense in respiratory specimens is not yet clear.

CASE PRESENTATION

To our knowledge, we, for the first time, described the identification of M. arupense from the pleural effusion of an immunocompetent patient, who presented with fever and chylothorax. The symptoms resolved with doxycycline treatment for 45 days and a low-fat, high-protein diet. Follow-up at 14 months showed no relapse.

CONCLUSIONS

Because the patient fully recovered without combined anti-NTM treatment, we did not consider M. arupense the etiological cause in this case. This indicates that M. arupense detected in pleural effusion is not necessarily a causative agent and careful interpretation is needed in terms of its clinical relevance.