Mycobacterium Tuberculosis In Central Ethiopia: Molecular Epidemiology, Drug Sensitivity Patterns, and Evaluation of the Genotype Mtbdrplus Assay for the Detection of Rifampicin and Isoniazid Resistance

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Addis Ababa University


Introduction: Identification of the types of strains of Mycobacterium tuberculosis (M. tuberculosis) complex causing tuberculosis (TB), determination of their drug sensitivity patterns and rapid identification of MDR strains could contribute to TB control program. Objective: the objective of this study was to identify the strains M. tuberculosis causing TB in central Ethiopia, determine their drug sensitivity patterns, and evaluate of the GenoType MTBDRplus assay for detecting of Rifampicin and Isoniazid resistance. Methodology: A total of 338 M. tuberculosis complex were isolated from pulmonary TB cases in central Ethiopia and 297 culture positive isolates were included in this study. The isolates were analyzed using region of difference (RD) 9-based polymerase chain reaction (PCR) and spoligotyping. Additionally, mycobacterial interspersed repetitive unit variable number tandem repeat (MIRU-VNTR) analysis was done on 29 isolates. The drug sensitivity pattern of the isolates was performed using conventional and molecular assay. Evaluation of MTBDRplus assay was done using conventional method as a gold standard. Results: The Mycobaterium isolates were majorly M.tuberculosis (98.6%) while only 1.4% was M. africanum. Ninety different patterns were identified, 45 were registered in SpolDB4 while 45 were not found in the database. Of these 90 spoligotypes, 32 were clustered consisting of 223 (79.3%) isolates while 58 had only a single isolate each. The dominant spoligotypes were SIT 53, SIT 149, and SIT 54 consisting of 43, 37 and 34 isolates, respectively. Majority (86.8%) of the isolates belonged to the Euro-American lineage followed by East-African-Indian (6.4%) and Indo-oceanic (5%) lineages. The result of MIRU-VENTR showed that isolates with similar spolygotype pattern showed difference in their copies of 24 MIRU loci. Of the 268 M. tuberculosis isolated from new cases, 59 (22.2%) were resistant to at least one of the first line drugs. The prevalence of multi-drug resistant (MDR) M. tuberculosis in new TB cases was 1.5% (4/268). The sensitivity and specificity of the GenoType MTBDRplus assay for the detection of Rifampicin resistant M. tuberculosis were 80.0% and 99.6%, respectively while they were 82.7% and 99.6%, respectively for the detection of Isoniazid (INH) resistant M. tuberculosis. Its sensitivity and specificity in detecting MDR M. tuberculosis were 75.0% and 100%, respectively, and its concordance with the conventional drug sensitivity test was 81.4%. Conclusion: The main cause of TB in human in central Ethiopia was M. tuberculosis. The majority of the M. tuberculosis isolates were found in clustered spoligotypes, which could suggest the possibility of on-going transmission in the study areas. A significant proportion of M. tuberculosis was resistant to at least one first line anti-TB drug warranting for improving the control program. GenoType MTBDRplus assay had an acceptable sensitivities and specificities for the detection of Rifampicin and Isoniazid resistant M. tuberculosis. Moreover, it had good concordance with the conventional drug sensitivity test suggesting its potential application for drug sensitivity test.



Central Ethiopia, Drug Sensitivity, Genotype Mtbdrplus Assay, Proportion Method, M. Tuberculosis, Strain Diversity