Mixed nontuberculous mycobacteria in an immunocompromised patient with probable progressive multifocal...

Nontuberculous mycobacteria (NTM) are increasingly recognized opportunistic pathogens found ubiquitously in the environment. The presence of multiple NTM species at the site of disease complicates diagnosis and treatment.

A 40-year-old patient who tested positive for HIV, with an absolute clusters of differentiation 4+ T-cell count of 3 cells/µl and cryptococcaemia, presented with hemoptysis, productive cough, and weight loss. Mixed NTM species, including Mycobacterium kansasii and Mycobacterium chelonae, were detected by the GenoType Mycobacterium Common Mycobacteria line probe assay from respiratory specimens, with Mycobacterium avium bacteremia also identified in the same month. An empirical regimen of azithromycin, ethambutol, isoniazid, and rifabutin was initiated to address recurrent positive cultures with M. kansasii and the NTM bacteremia. Despite this treatment, the patient experienced neurologic deterioration, was diagnosed with probable progressive multifocal leukoencephalopathy, and subsequently died.

Advanced diagnostic techniques, including Sanger sequencing, Deeplex Myc-TB in combination with short-read next-generation sequencing, and targeted amplicon-based Oxford Nanopore Technologies long-read sequencing, revealed the presence of mixed NTM species in two retrospective stored cultures, with variations in primer binding affinity among the M. kansasii and M. avium.

This case highlights the individualized considerations required to manage a patient with mixed NTM infection and the need for multi-target diagnostic approaches.