Extensively Drug-Resistant Tuberculosis in California, 1993-2006

Clin Infect Dis. 2008 Aug 15;47(4):450-7. doi: 10.1086/590009.


Background: Extensively drug-resistant (XDR) tuberculosis (TB) is a global public health emergency. We investigated the characteristics and extent of XDR TB in California to inform public health interventions.

Methods: XDR TB was defined as TB with resistance to at least isoniazid, rifampin, a fluoroquinolone, and 1 of 3 injectable second-line drugs (amikacin, kanamycin, or capreomycin). Pre-XDR TB was defined as TB with resistance to isoniazid and rifampin and either a fluoroquinolone or second-line injectable agent but not both. We analyzed TB case reports submitted to the state TB registry for the period 1993-2006. Local health departments and the state TB laboratory were queried to ensure complete drug susceptibility reporting.

Results: Among 424 multidrug-resistant (MDR) TB cases with complete drug susceptibility reporting, 18 (4.2%) were extensively drug resistant, and 77 (18%) were pre-extensively drug resistant. The proportion of pre-XDR TB cases increased over time, from 7% in 1993 to 32% in 2005 (P = .02)). Among XDR TB cases, 83% of cases involved foreign-born patients, and 43% were diagnosed in patients within 6 months after arrival in the United States. Mexico was the most common country of origin. Five cases (29%) of XDR TB were acquired during therapy in California. All patients with XDR TB had pulmonary disease, and most had prolonged infectious periods; the median time for conversion of sputum culture results was 195 days. Among 17 patients with known outcomes, 7 (41.2%) completed therapy, 5 (29.4%) moved, and 5 (29.4%) died. One patient continues to receive treatment.

Conclusions: XDR TB and pre-XDR TB cases comprise a substantial fraction of MDR TB cases in California, indicating the need for interventions that improve surveillance, directly observed therapy, and rapid drug susceptibility testing and reporting.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Antitubercular Agents / pharmacology
  • Antitubercular Agents / therapeutic use
  • California / epidemiology
  • California / ethnology
  • Child
  • Child, Preschool
  • Culture Media
  • Disease Notification
  • Emigration and Immigration
  • Extensively Drug-Resistant Tuberculosis* / drug therapy
  • Extensively Drug-Resistant Tuberculosis* / epidemiology
  • Extensively Drug-Resistant Tuberculosis* / ethnology
  • Extensively Drug-Resistant Tuberculosis* / microbiology
  • Humans
  • Infant
  • Mexico
  • Microbial Sensitivity Tests
  • Middle Aged
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / isolation & purification*
  • Population Surveillance
  • Registries / statistics & numerical data
  • Tuberculosis, Multidrug-Resistant / epidemiology
  • Tuberculosis, Multidrug-Resistant / ethnology
  • Tuberculosis, Multidrug-Resistant / microbiology
  • Tuberculosis, Pulmonary* / drug therapy
  • Tuberculosis, Pulmonary* / epidemiology
  • Tuberculosis, Pulmonary* / ethnology
  • Tuberculosis, Pulmonary* / microbiology


  • Antitubercular Agents
  • Culture Media