The role of nontuberculous mycobacteria in the diagnosis, management and quantifying risks of tuberculosis in Tanga, Tanzania

Abstract

Background: The role of nontuberculous mycobacteria (NTM) in tuberculosis (TB) diagnosis is well documented in many developing settings. However, this has not been the case in many resource poor settings like Tanzania. This study aimed at understanding the role of NTM in the diagnosis and management of TB in resource poor settings of Tanzania.

Methods: A cross‑sectional study was conducted in Tanga, Tanzania. Patients with symptoms suggestive of TB self-referred to health care facilities were recruited. Two sputum samples were collected for standard direct smear microscopy. Culture was performed using BacT/Alert 3D system, Löwenstein-Jensen and Gottsacker slopes. Identification of Mycobacterium tuberculosis and NTM was done by using GenoType^®MTBC and GenoType^®CM/AS, respectively.

Results: A total of 372 patients were involved in the study. Eighty-one (21.8%) patients were diagnosed as having M. tuberculosis by the isolation of the organism from cultures of sputum. Further analysis of culture showed that 8.1% (30/372) were NTM with 7/372 (1.9%) cases of NTM classified as pulmonary tuberculosis (PTB) patients. Ziehl Neelsen stain had a sensitivity of 68.8% and produced 10 false negative results. On the other hand, Fluorescence stain had a sensitivity of 85.7% and gave seven false negative samples when compared with culture results. Weight loss (p = 0.0001), fatigue (p = 0.003), fever (p = 0.038) and night sweats (p = 0.004), young population (18-40 years) (p = 0.0352), males (p = 0.0025) were important risk factors for TB. Four out of 30 NTM diagnosed by culture received first line anti‑TB treatment suggesting that a good proportion of patients (4/65, 6.2%) were mistreated as TB patients.

Conclusion: Inefficient screening of TB patients in resource poor settings and prevalent increase of NTM may contribute to over diagnosis of TB cases. The need to integrate NTM diagnosis in the routine management of TB is urgently needed for designing effective tuberculosis prevention and control strategies in the country.