Disseminated infection with Mycobacterium tilburgii in an immunocompromized host: A case analysis and review of the literature

A 42 y. o. male HIV-seropositive (CDC B3, viral load 277 HIV-RNA copies/ml; 32 CD4+ T-cells/microL) patient presented with a 6 months history of 10kg weight loss and intermittend diarrhea. An outpatient computed tomography revelead thoracic and abdominal lymphadenopathy and ultrasound guided transbronchial mediastinal lymphnode (LN) fine needle biopsy showed massive numbers of acid-fast bacilli (AFBs) on direct smears. With a presumptive diagnosis of LN tuberculosis the patient was referred to our hospital for the initiation of antituberculous drug treatment.

However, Mycobacterium tuberculosis (MTB) specific nucleic acid could not be amplified from the LN aspirate and early-secretory-target-6 and culture-filtrate-protein-10-specific enzyme linked immunospot assays were unreactive when performed on bronchoalveolar lavage and peripheral blood mononuclear cells. Esophago-gastroduodenoscopy showed cottage-cheese-like appearance of the duodenal mucosa. Despite the fact that massive numbers of AFBs where also observed in the duodenal biopsy, mycobacteria could not be cultivated on standard mycobacteria media from the duodenal mucosa or the LN aspirate. Sequencing of bacterial 16sRNA identified the pathogenic bacterium as the non cultivatable Mycobacterium tilburgii. Combination antimycobacterial treatment with rifabutin, ethambutol and azithromycin resulted in clinical improvement and resolution of the lesions.

Although rarely described because of diagnostic difficulties, M. tilburgii infections must be considered in the differential diagnosis of immunocompromized hosts with generalized lymphadenopathy and ongoing diarrhea.