<i>Mycobacterium colombiense</i> isolation among people living with human immunodeficiency virus: a case series

Mycobacterium colombiense is a seldom reported non-tuberculous mycobacteria causing infections mostly in immunosuppressed patients. Thus, we present the findings of three M. colombiense isolation cases from a third-level hospital in Monterrey, Mexico, during 2020–2024. Mycobacterial identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and Anyplex™ MTB/NTM Real-time Detection. Patients were people living with Human Immunodeficiency Virus (PLHIV), with pneumonia and lymphadenopathy. Patients had high HIV viral loads and low CD4 counts (21–103 cells/mm3). None of the cases had specific Mycobacterium avium complex (MAC) treatment, and all of them showed clinical improvement. Current non-tuberculous mycobacteria discrimination tests may not effectively diagnose significant pathogens like M. colombiense, potentially leading to delays in treatment and negatively impacting patient outcomes.