title: Transmission of multidrug-resistant and extensively drug-resistant tuberculosis in a metropolitan city.
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.
authors.affiliation: Dept of Health, Tuberculosis and Chest Service, Centre for Health Protection, Hong Kong. eric_leung@dh.gov.hk
authors.forename: Eric Chung Ching
authors.initials: EC
authors.lastname: Leung
authors.forename: Chi Chiu
authors.initials: CC
authors.lastname: Leung
authors.forename: Kai Man
authors.initials: KM
authors.lastname: Kam
authors.forename: Wing Wai
authors.initials: WW
authors.lastname: Yew
authors.forename: Kwok Chiu
authors.initials: KC
authors.lastname: Chang
authors.forename: Wai Man
authors.initials: WM
authors.lastname: Leung
authors.forename: Cheuk Ming
authors.initials: CM
authors.lastname: Tam
mesh_terms: D000328:Adult; D002947:Cities; D016000:Cluster Analysis; D015331:Cohort Studies; D016358:Contact Tracing; D054908:Extensively Drug-Resistant Tuberculosis / Q000635:transmission*; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D007538:Isoniazid / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis; D012150:Polymorphism, Restriction Fragment Length; D015995:Prevalence; D012189:Retrospective Studies; D013307:Streptomycin / Q000494:pharmacology; D018088:Tuberculosis, Multidrug-Resistant / Q000635:transmission*; D014505:Urban Population
chemical_list: D007538:Isoniazid; D013307:Streptomycin