Abstract:
Background:Ethiopia has an extremely high rate of extrapulmonary tuberculosis, dominated by tuberculous
lymphadenitis (TBLN). However, little is known about Mycobacterium tuberculosiscomplex (MTBc) lineages responsible for TBLN in Southwest Ethiopia.
Methods:A total of 304 MTBc isolates from TBLN patients in Southwest Ethiopia were genotyped primarily by
spoligotyping. Isolates of selected spoligotypes were further analyzed by 15-loci mycobacterial interspersed
repetitive unit–variable number tandem repeat (MIRU-VNTR) (n = 167) and qPCR-based single nucleotide
polymorphism (n = 38). Isolates were classified into main phylogenetic lineages and families by using the reference strain collections and identification tools available atMIRU-VNTRplusdata base. Resistance to rifampicin
was determined by Xpert MTB/RIF.
Results:The majority of isolates (248; 81.6%) belonged to the Euro-American lineage (Lineage 4), with the illdefined T and Haarlem as largest families comprising 116 (38.2%) and 43 (14.1%) isolates respectively. Of the T
family, 108 isolates were classified as being part of the newly described Ethiopian families, namely Ethiopia_2
(n = 44), Ethiopia_3 (n = 34) and Ethiopia_H37Rv-like (n = 30). Other sub-lineages included URAL (n = 18), S
(n = 17), Uganda I (n = 16), LAM (n = 13), X (n = 5), TUR (n = 5), Uganda II (n = 4) and unknown (n = 19).
Lineage 3 (Delhi/CAS) was the second most common lineage comprising 44 (14.5%) isolates. Interestingly, six
isolates (2%) were belonged to Lineage 7, unique to Ethiopia. Lineage 1 (East-African Indian) and Lineage 2
(Beijing) were represented by 3 and 1 isolates respectively. M. boviswas identified in only two (0.7%) TBLN
cases. The cluster rate was highest for Ethiopia_3 isolates showing clonal similarity with isolates from North
Ethiopia. Lineage 3 was significantly associated with rifampicin resistance.
Conclusions:In TBLN in Southwest Ethiopia, the recently described Ethiopia specific Lineage 4 families were
predominant, followed by Lineage 3 and Lineage 4-Haarlem. The contribution ofM. bovisin TBLN infection is
minimal.
