Transmission of multidrug-resistant and extensively drug-resistant tuberculosis in a metropolitan city

Eur Respir J. 2013 Apr;41(4):901-8. doi: 10.1183/09031936.00071212. Epub 2012 Aug 9.

Abstract

Multidrug-resistant (MDR)- tuberculosis (TB) and extensively drug resistant (XDR)-TB reportedly lead to increased household transmission. This is a retrospective cohort study of active TB occurring among household contacts exposed to MDR-TB. Of 704 contacts in 246 households, initial screening identified 12 (1.7%) TB cases (prevalent cases) and 17 (2.4%) contacts that subsequently developed active TB (secondary cases) after a median (range) duration of 17 (5-62.5) months. Eight prevalent cases and three secondary cases had MDR-TB. TB incidence rates per 100,000 person-years were 254.9 overall and 45.0 for MDR-TB. XDR-TB in the index MDR-TB patient significantly increased the odds of identifying a prevalent TB case to 4.8 (95% CI 1.02-22.5), and the hazard of finding a secondary TB case to 4.7 (95% CI 1.7-13.5). Molecular fingerprinting confirmed household transmission of MDR-TB. Of 20 retrievable isolates from 27 XDR-TB index cases, restriction fragment length polymorphism analysis showed clustering among 13 (65%), with 11 (55%) due to recent transmission by n-1 method and an identifiable household source in only three (27.2%) of the 11 cases. XDR-TB relative to MDR-TB significantly increases household transmission of TB, probably reflecting prolonged/higher infectivity, and indicating a need for prolonged household surveillance. XDR-TB may largely transmit outside of the household settings.

MeSH terms

  • Adult
  • Cities
  • Cluster Analysis
  • Cohort Studies
  • Contact Tracing
  • Extensively Drug-Resistant Tuberculosis / transmission*
  • Female
  • Hong Kong / epidemiology
  • Humans
  • Isoniazid / pharmacology
  • Male
  • Middle Aged
  • Mycobacterium tuberculosis
  • Polymorphism, Restriction Fragment Length
  • Prevalence
  • Retrospective Studies
  • Streptomycin / pharmacology
  • Tuberculosis, Multidrug-Resistant / transmission*
  • Urban Population

Substances

  • Isoniazid
  • Streptomycin