Colonization or coinfection? A case report of <i>Mycobacterium avium</i> complex detected in a patient with pulmonary tuberculosis

Background Nontuberculous mycobacteria (NTM) infections have been increasingly reported in the literature; however, isolation of both NTM and Mycobacterium tuberculosis complex (MTBC) in respiratory samples may indicate transient NTM colonization rather than true coinfection. Distinguishing between NTM colonization and true infection is necessary for guiding appropriate antimicrobial treatment regimen. Case summary Here, we describe a case of a 41-year-old immunocompetent female with pulmonary tuberculosis in which Mycobacterium avium and Mycobacterium intracellulare , both members of the M. avium complex (MAC), were independently identified with MTBC in two of three sputum cultures using Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). After completing MTBC-targeted therapy, the patient fully returned to her baseline physical activity, and all subsequent cultures were negative for MTBC and MAC. Conclusion This case study underscores the challenges in the adjudication of colonization from coinfection in mixed mycobacterial specimens. Although there are microbiological guidelines for diagnosing independent NTM infections and MTBC infections, there is an unmet need for guidance on diagnosing and treating NTM in patients with pulmonary tuberculosis.