Differentiation and Characterization of Mycobacterium tuberculosis Complex Causing Pulmonary Tuberculosis across North Central Nigeria

Aims: To differentiate and Characterize Mycobacterium tuberculosis complex causing pulmonary tuberculosis across North Central Nigeria

Study Design: This was a simple descriptive health-based study that involved clinically suspected tuberculosis patients who were referred to two selected General Hospitals for diagnosis in each of the states across North Central Nigeria.

Place and Duration of Study: This study was carried out in the North Central zone of Nigeria and it included all the seven States across North Central Nigeria using two General Hospitals per state. The study included 371 positive sputum samples drawn from 2800 suspected pulmonary TB patients between 2017 and 2018.

Methodology: A total of 371 GeneXpert positive sputa for TB were decontaminated using N Acetyl Cysteine and Sodium Hydroxide under a level 3 Bio-safety cabinet and the resulting sediment was cultured on Lowestein- Jensen (LJ) media containing glycerol and pyruvate at 37ºC in a slanted position, SD- Bioline (TB Ag MPT 64) for the differentiation of MTBC from NTM was carried out using the isolates from LJ culture. Evaluation of speciation was done using Line Probe Assay to determine the predominant species of MTBC. All the protocols used in this study followed the manufacturer’s manual strictly.

Results: A total of 371 decontaminated positive GeneXpert sputa derived from 2800 suspected PTB participants were cultured on Lowestein- Jensen (LJ) medium and 302(81.40%) was found positive while 69(18.60%) were found negative. Out of the culture positive isolates, 288 (95.36%) isolates were detected on SD-BIOLINE TB Ag MPT 64 ® assay for MTBC and 14 (4.64%) as NTM. Of the 288 MTBC, three different species were identified; 272 (94.64%) were M. tuberculosis/M. Canetti, 7 (2.43%) were M. africanum and 9(3.13) showed a no MTBC reaction band on all the samples that were analysed.

Conclusion: Differentiations of MTBC from NTM has help to re-confirm that not all symptoms of pulmonary infection are caused by MTBC but NTM are implicated due to their distribution in the environment, however, molecular characterisation method has narrow our findings down to M. tuberculosis/M. canettii as the predominant specie of MTBC circulating in the region, although, M. africaum was also detected and these two species of MTBC are the leading cause of pulmonary tuberculosis across all the North Central state of Nigeria.