Mycobacterial lineages causing pulmonary and extrapulmonary tuberculosis, Ethiopia

Abstract

Molecular typing of 964 specimens from patients in Ethiopia with lymph node or pulmonary tuberculosis showed a similar distribution of Mycobacterium tuberculosis strains between the 2 disease manifestations and a minimal role for M. bovis. We report a novel phylogenetic lineage of M. tuberculosis strongly associated with the Horn of Africa.

Keywords: Ethiopia; Mycobacterium bovis; Mycobacterium tuberculosis; TB lymphadenitis; Tuberculosis and other mycobacteria; bacteria; bovine; cervical lymph nodes; extrapulmonary tuberculosis; lineage; lymph nodes; pulmonary tuberculosis; tuberculosis; zoonoses; zoonotic transmission.

Figure 1

Lineages of the Mycobacterium tuberculosis (MTB) complex, Ethiopia, 2006–2010. Genome sequence analysis of 4 strains representative of 36 related isolates identified them as members of a new phylogenetic lineage (lineage 7) of M. tuberculosis, which has a phylogenetic location intermediate between ancient lineage 1 and modern Lineages 2, 3, and 4, and a branch point before the deletion of the TbD1 region (3). Nomenclatures for lineage names and numbers are as proposed (4,6). Phylogeny shown is based on 13,199 nt positions that were variable in at least 1 of the 28 M. tuberculosis complex strains represented in the tree. Numbers near nodes indicate percentage of bootstrap replicates supporting the topology after 1,000 pseudoreplicates. MAF, M. africanum; MBO, M. bovis.

Figure 2

Mycobacterial interspersed repetitive unit–variable number tandem repeat (MIRU-VNTR) networks of major spoligotype clusters, Ethiopia, 2006–2010. Two large spoligotype clusters from lineage 4 (A) (90 isolates of sopligotype 149) and lineage 3 (B) (73 isolates of spoligotype 25) were further characterized by 24-loci MIRU-VNTR typing (Technical Appendix Table 2). Minimum-spanning trees were calculated for each cluster by using MIRU-VNTRplus (www.miru-vntrplus.org). Each circle indicates an individual genotype. Genotypes L and E1 include >15 isolates and remaining genotypes include <15 isolates. Genotypes indicated by a black circle were isolated from patients with pulmonary tuberculosis (TB); those in light gray were isolated from patients with TB lymphadenitis in cervical lymph nodes (TBLN); and those in dashed circles were isolated from patients with pulmonary TB and those with TBLN. Numbers on lines between circles indicate distance between 2 genotypes.