Molecular typing of mycobacteria isolated from tuberculous lymphadenitis cases in Addis Ababa, Ethiopia

BACKGROUND: In Ethiopia, one of the world's 22 high tuberculosis (TB) burden countries, one third of the tuberculosis (TB) cases are attributed to tuberculosis lymphadenitis (TBLN). However, information on the molecular type of the mycobacterial species and strains that cause TBLN in the country is scarce. OBJECTIVE: To identify the species and strains of mycobacteria that cause TBLN in Ethiopia. METHODS AND RESULTS: A cross-sectional study was conducted among 206 presumed TBLN cases to characterise positive culture isolates. Mycobacterium tuberculosis complex species and strains were identified using region of difference 9 deletion and SITVIT WEB, respectively. Of the 206 fine-needle aspirate samples collected, 74 (36%) were culture-positive: 73 (98.6%) of the isolates were M. tuberculosis, and the remaining 1.4% were M. bovis. Further characterisation of the 73 M. tuberculosis isolates led to 26 distinct spoligotype international types (SITs) and 13 newly identified patterns. The most prevalent strains were SIT149, SIT53, SIT26 and SIT37 of sublineages T3-ETH, T1, CASI-Delhi and T3, respectively; these accounted for 52.6% of the total number of strains. CONCLUSION: TBLN was mainly caused by M. tuberculosis and highly clustered strains SIT149, SIT53, SIT26 and SIT37 of sublineages T3-ETH, T1, CASIDelhi and T3, respectively.