title: Molecular epidemiology and transmission dynamics of Mycobacterium tuberculosis in Northwest Ethiopia: new phylogenetic lineages found in Northwest Ethiopia.
abstract: BACKGROUND
  Although Ethiopia ranks seventh among the world's 22 high-burden tuberculosis (TB) countries, little is known about strain diversity and transmission. In this study, we present the first in-depth analysis of the population structure and transmission dynamics of Mycobacterium tuberculosis strains from Northwest Ethiopia.
  
  
  METHODS
  In the present study, 244 M. tuberculosis isolates where analysed by mycobacterial interspersed repetitive unit - variable number tandem repeat 24-loci typing and spoligotyping methods to determine phylogenetic lineages and perform cluster analysis. Clusters of strains with identical genotyping patterns were considered as an indicator for the recent transmission.
  
  
  RESULTS
  Of 244 isolates, 59.0% were classified into nine previously described lineages: Dehli/CAS (38.9%), Haarlem (8.6%), Ural (3.3%), LAM (3.3%), TUR (2.0%), X-type (1.2%), S-type (0.8%), Beijing (0.4%) and Uganda II (0.4%). Interestingly, 31.6% of the strains were grouped into four new lineages and were named as Ethiopia_3 (13.1%), Ethiopia_1 (7.8%), Ethiopia_H37Rv like (7.0%) and Ethiopia_2 (3.7%) lineages. The remaining 9.4% of the isolates could not be assigned to the known or new lineages. Overall, 45.1% of the isolates were grouped in clusters, indicating a high rate of recent transmission.
  
  
  CONCLUSIONS
  This study confirms a highly diverse M. tuberculosis population structure, the presence of new phylogenetic lineages and a predominance of the Dehli/CAS lineage in Northwest Ethiopia. The high rate of recent transmission indicates defects of the TB control program in Northwest Ethiopia. This emphasizes the importance of strengthening laboratory diagnosis of TB, intensified case finding and treatment of TB patients to interrupt the chain of transmission.
authors.affiliation: Department of Medical Microbiology, College of Medicine and Health Sciences, University of Gondar, Gondar, Ethiopia. bt1488@yahoo.com
authors.forename: Belay
authors.initials: B
authors.lastname: Tessema
authors.forename: Joerg
authors.initials: J
authors.lastname: Beer
authors.forename: Matthias
authors.initials: M
authors.lastname: Merker
authors.forename: Frank
authors.initials: F
authors.lastname: Emmrich
authors.forename: Ulrich
authors.initials: U
authors.lastname: Sack
authors.forename: Arne C
authors.initials: AC
authors.lastname: Rodloff
authors.forename: Stefan
authors.initials: S
authors.lastname: Niemann
mesh_terms: D000328:Adult; D000995:Antitubercular Agents / Q000494:pharmacology; D016000:Cluster Analysis; D024881:Drug Resistance, Bacterial; D005002:Ethiopia / Q000453:epidemiology; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009169:Mycobacterium tuberculosis / Q000145:classification* / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification; D010802:Phylogeny; D014376:Tuberculosis / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*
chemical_list: D000995:Antitubercular Agents