Prevalence of Nontuberculous Mycobacteria Infections in Patients Diagnosed with Pulmonary Tuberculosis in Ibadan

Introduction: Nontuberculous mycobacteria (NTM) are mycobacteria species other than the Mycobacterium tuberculosis complex (MTC); they are opportunistic pathogens and cause life threatening infections with symptoms that mimic those of tuberculosis (TB). Paradoxically, the routine diagnostic tools for TB in Nigeria cannot differentiate MTC from NTM; Hence, TB patients with NTM infections are sometimes incorrectly diagnosed as TB.

Aim: To determine the prevalence of NTM among routinely diagnosed pulmonary TB patients attending the Directly Observed Treatment Short-course (DOTS) centres in Ibadan, Nigeria.

Materials and Methods: This was a cross sectional study conducted at the Tuberculosis Research Laboratory, Department of Veterinary Public Health and Preventive Medicine, University of Ibadan. Sputum samples were collected consecutively from 319 suspected TB patients with or without human immunodeficiency virus (HIV) between January 2010 and November 2011 on clinical visits to eight DOTS centres in Ibadan. The samples were cultured on Lowenstein-Jensen medium for about 4-8 weeks after decontamination using N-acetyl-L-cystein-NaOH method. Molecular characterisation of the isolates was done using genus typing. Data obtained were analysed using STATA 12.

Results: In all, a total of 149 isolates were obtained, 26 (17.4%) were identified as NTM; 11 (7.4%) of which were from HIV positive patients, 3 (2.0%) from non HIV patients and 12 (8.0%) unknown cases. The univariable analysis showed association between isolation of NTM and center as well as case. Subjects screened at Ade Oyo (OR=3.5; 95%CI: 1.1-11.8) showed higher likelihood of being infected with NTM.

Conclusion: The high prevalence of NTM among patients earlier diagnosed as PTP following the diagnostic algorithm used in DOTS centers in Nigeria underscores the need for nationwide studies to determine the prevalence of NTM among suspected TB patients. The integration of culture and molecular techniques to improve on the diagnostic algorithm for TB management and control in Nigeria is hereby recommended.