AB 85. Presentation of cases of non tuberculous mycobacteria lung disease in immunocompetent patients

Background: Nontuberculous mycobacteria (NTM) are acidfast microorganisms that commonly cause lung disease in immunocompromised patients and patients with preexisting structural lung disease. Four cases of NTM infection in immunocompetent patients are presented.

Patients and methods: Case 1. A 62-year-old patient with clinical and radiological features compatible with tuberculosis (TB) and positive sputum smear for acid-fast bacilli was treated with first-line agents. After three months and while the patient was improving M. intracellulare resistant to macrolides was identified in two culture samples. Targeted therapy was initiated 6 months after the onset of symptoms. Case 2. A 48-year-old man, already under antiTB treatment for 6 months, was evaluated due to clinical and radiological lack of improvement. Radiological findings were suggestive of TB but there was no microbiological verification. M. intracellulare resistant to macrolides was identified. Targeted therapy was initiated 9 months after the onset of symptoms. Case 3. A 73-year-old patient, with history of TB 8 and 2 years ago and known resistance to rifampicin, presented with clinical findings of TB and positive sputum for acid-fast bacilli. Empirical therapy with second line antiTB agents was initiated. The negative nucleic acid amplification test for M. tuberculosis and the absence of clinical improvement led to identification of M. kansasii. Targeted therapy was initiated 3 months after the onset of symptoms. Case 4. A 60-year-old patient with bronchiectasis and a history of recurrent respiratory infections over 10 years, presented with clinical and radiological findings consistent with TB. Treatment with first-line antiTB agents was initiated without laboratory confirmation. M. avium was identified by molecular methods. Targeted therapy was initiated 1.5 months after initial evaluation, whereas the patient΄s history of recurrent infections could be attributed to M. avium.

Conclusions: NTM can cause infection even to immunocompetent individuals without structural lung disease. NTM infection cannot be differentiated from TB based on clinical and radiological features. Therefore diagnosis is based on NTM identification by molecular methods. Therapy and prognosis are different from TB. Mycobacterial identification is an important part of the diagnostic algorithm of tuberculosis.