title: Genotypic diversity of extensively drug-resistant tuberculosis (XDR-TB) in South Africa.
abstract: METHODS
  The epidemiology of extensively drug-resistant tuberculosis (XDR-TB), an emerging threat to TB control, is not well understood.
  
  
  OBJECTIVE
  To gain insight into the genotypic population structure of XDR Mycobacterium tuberculosis strains in South Africa using a molecular approach and thereby determine whether XDR-TB is mainly acquired or transmitted.
  
  
  METHODS
  Sputum isolates from patients with multidrug-resistant tuberculosis (MDR-TB) were submitted to the National Referral Laboratory for second-line drug susceptibility testing. The XDR-TB isolates were spoligotyped and these data were compared to the geographic origin of the isolate.
  
  
  RESULTS
  Of the 699 MDR-TB isolates submitted for testing between June 2005 and December 2006, 101 (17%) patients had a culture that was resistant to either ofloxacin or kanamycin, and 41 (6%) were resistant to both drugs (XDR-TB). Spoligotyping of the XDR-TB isolates identified 17 genotypes. As a result of the high genotypic diversity and geographical distribution, we estimate that between 63% and 75% of cases developed XDR-TB through acquisition.
  
  
  CONCLUSIONS
  Acquisition of extensive drug resistance appears to be the primary mechanism driving the XDR-TB epidemic in South Africa. This urgent TB control issue has to be addressed to prevent the spread of this potentially incurable disease.
authors.affiliation: Clinical Microbiology and Infectious Disease, National Health Laboratory Services, University of the Witwatersrand, Johannesburg, Gauteng, South Africa.
authors.forename: C K
authors.initials: CK
authors.lastname: Mlambo
authors.forename: R M
authors.initials: RM
authors.lastname: Warren
authors.forename: X
authors.initials: X
authors.lastname: Poswa
authors.forename: T C
authors.initials: TC
authors.lastname: Victor
authors.forename: A G
authors.initials: AG
authors.lastname: Duse
authors.forename: E
authors.initials: E
authors.lastname: Marais
mesh_terms: D000995:Antitubercular Agents / Q000627:therapeutic use; D004269:DNA, Bacterial / Q000032:analysis*; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D054908:Extensively Drug-Resistant Tuberculosis / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D005838:Genotype; D006801:Humans; D007612:Kanamycin / Q000627:therapeutic use; D009169:Mycobacterium tuberculosis / Q000145:classification / Q000235:genetics*; D015242:Ofloxacin / Q000627:therapeutic use; D010641:Phenotype; D013019:South Africa / Q000453:epidemiology; D013183:Sputum / Q000382:microbiology
chemical_list: D000995:Antitubercular Agents; D004269:DNA, Bacterial; D007612:Kanamycin; D015242:Ofloxacin