The impact of nontuberculous mycobacteria on management of presumed pulmonary tuberculosis.

Background: The presence of nontuberculous mycobacteria (NTM) in sputum or bronchial washings may cause diagnostic problems which affect clinical management.

Patients And Methods: In a retrospective analysis of 135 patients in a Dutch tuberculosis center, patients with NTM isolates were thoroughly investigated. Colonization or contamination by NTM was differentiated from true lung disease.

Results: 25 HIV-seronegative and two HIV-seropositive patients with NTM were identified. NTM were a likely cause of disease in only 14 (52%) patients. In 15 (55%), their presence led to preliminary diagnosis and treatment of tuberculosis. Unnecessary or inappropriate treatment was instituted in 17 (63%) patients with NTM. In two patients, detection of NTM in sputum also led to delay in diagnosing malignant disease.

Conclusion: In this series, NTM in sputum or bronchial washings poorly reflected disease and often led to diagnostic and therapeutic errors. Although it is common knowledge that the presence of NTM should be considered in smear-positive patients, this apparently is a diagnostic pitfall in clinical practice. Reliable DNA-based techniques and better communication between physicians and microbiologists may improve management of suspected mycobacterial infections.