Failure to Recognize Nontuberculous Mycobacteria Leads to Misdiagnosis of Chronic Pulmonary Tuberculosis

BACKGROUND: Nontuberculous mycobacterial (NTM) infections cause morbidity worldwide. They are difficult to diagnose in resource-limited regions, and most patients receive empiric treatment for tuberculosis (TB). Our objective here is to evaluate the potential impact of NTM diseases among patients treated presumptively for tuberculosis in Mali. METHODS: We re-evaluated sputum specimens among patients newly diagnosed with TB (naïve) and those previously treated for TB disease (chronic cases). Sputum microscopy, culture and Mycobacterium tuberculosis drug susceptibility testing were performed. Identification of strains was performed using molecular probes or sequencing of secA1 and/or 16S rRNA genes. RESULTS: Of 142 patients enrolled, 61 (43%) were clinically classified as chronic cases and 17 (12%) were infected with NTM. Eleven of the 142 (8%) patients had NTM disease alone (8 M. avium, 2 M. simiae and 1 M. palustre). All these 11 were from the chronic TB group, comprising 11/61 (18%) of that group and all were identified as candidates for second line treatment. The remaining 6/17 (35.30%) NTM infected patients had coinfection with M. tuberculosis and all 6 were from the TB treatment naïve group. These 6 were candidates for the standard first line treatment regimen of TB. M. avium was identified in 11 of the 142 (8%) patients, only 3/11 (27.27%) of whom were HIV positive. CONCLUSIONS: NTM infections should be considered a cause of morbidity in TB endemic environments especially when managing chronic TB cases to limit morbidity and provide appropriate treatment

<i>Mycobacterial species</i> isolated, demographic characteristics, symptoms and treatment assigned to each patient.

@<p><i>Mycobacterium species</i> most closely related;</p>*<p>Patients were naïve to TB treatment before they were enrolled in the study and received the TB standard regimen for their disease.</p>$<p>Based on National treatment guidelines for TB, the Standard regimen comprises 2 months of rifampin, isoniazid, pyrazinamide and ethambutol and 4 months of isoniazid and rifampin (2RHZE/4RH). Patients with sputum smears positive at month-5 of standard regimen, receive 1 month of rifampin, isoniazid, pyrazinamide, ethambutol and streptomycin followed by 2 months of rifampin, isoniazid, pyrazinamide, ethambutol and 5 months of rifampin, isoniazid and ethambutol (2RHZES/1RHZE/5RHE called re-treatment regimen). The second line treatment for chronic cases (patients with sputum smears positive after re-treatment regimen) comprises kanamycin, ofloxacin, ethionamide and pyrazinamide (3KOEtZ/18OetZ) for MDR disease. <i>M.af: Mycobacterium africanum</i>; <i>M.tb: Mycobacterium tuberculosis</i>; <i>Neg: negative</i>; <i>Pos: positive</i>; <i>AFB: acid-fast bacilli.</i></p

Impact of NTM on TB sputum smears or cultures.

<p><i>NTM: Nontuberculous mycobacteria</i>; <i>MTBC: Mycobacterium tuberculosis</i> complex;</p>*<p><i>Pos: positive in at least two occasions</i>;</p>#<p><i>Neg: negative in three occasions</i>.</p

Distribution of patients in the naïve and chronic treatment groups based on culture and susceptibility results.

*<p><i>M. tuberculosis</i> complex,</p>#<p>Resistant to isoniazid and rifampin,</p>@<p>Nontuberculous Mycobacteria.</p