title: Extensively drug-resistant tuberculosis in the United States, 1993-2007.
abstract: BACKGROUND
  Worldwide emergence of extensively drug-resistant tuberculosis (XDR-TB) has raised global public health concern, given the limited therapy options and high mortality.
  
  
  OBJECTIVE
  To describe the epidemiology of XDR-TB in the United States and to identify unique characteristics of XDR-TB cases compared with multidrug-resistant TB (MDR-TB) and drug-susceptible TB cases.
  
  
  METHODS
  Descriptive analysis of US TB cases reported from 1993 to 2007. Extensively drug-resistant TB was defined as resistance to isoniazid, a rifamycin, a fluoroquinolone, and at least 1 of amikacin, kanamycin, or capreomycin based on drug susceptibility test results from initial and follow-up specimens.
  
  
  METHODS
  Extensively drug-resistant TB case counts and trends, risk factors for XDR-TB, and overall survival.
  
  
  RESULTS
  A total of 83 cases of XDR-TB were reported in the United States from 1993 to 2007. The number of XDR-TB cases declined from 18 (0.07% of 25 107 TB cases) in 1993 to 2 (0.02% of 13 293 TB cases) in 2007, reported to date. Among those with known human immunodeficiency virus (HIV) test results, 31 (53%) were HIV-positive. Compared with MDR-TB cases, XDR-TB cases were more likely to have disseminated TB disease (prevalence ratio [PR], 2.06; 95% confidence interval [CI], 1.19-3.58), less likely to convert to a negative sputum culture (PR, 0.55; 95% CI, 0.33-0.94), and had a prolonged infectious period (median time to culture conversion, 183 days vs 93 days for MDR-TB; P < .001). Twenty-six XDR-TB cases (35%) died during treatment, of whom 21 (81%) were known to be HIV-infected. Mortality was higher among XDR-TB cases than among MDR-TB cases (PR, 1.82; 95% CI, 1.10-3.02) and drug-susceptible TB cases (PR, 6.10; 95% CI, 3.65-10.20).
  
  
  CONCLUSIONS
  Although the number of US XDR-TB cases has declined since 1993, coinciding with improved TB and HIV/AIDS control, cases continue to be reported each year.
authors.affiliation: Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, 1600 Clifton Rd, Mailstop E-10, Atlanta, GA 30333, USA.
authors.forename: N Sarita
authors.initials: NS
authors.lastname: Shah
authors.forename: Robert
authors.initials: R
authors.lastname: Pratt
authors.forename: Lori
authors.initials: L
authors.lastname: Armstrong
authors.forename: Valerie
authors.initials: V
authors.lastname: Robison
authors.forename: Kenneth G
authors.initials: KG
authors.lastname: Castro
authors.forename: J Peter
authors.initials: JP
authors.lastname: Cegielski
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000188:drug therapy / Q000453:epidemiology / Q000401:mortality; D000293:Adolescent; D000328:Adult; D000368:Aged; D000995:Antitubercular Agents / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D023801:Directly Observed Therapy; D054908:Extensively Drug-Resistant Tuberculosis / Q000188:drug therapy / Q000453:epidemiology* / Q000401:mortality; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D011159:Population Surveillance; D012307:Risk Factors; D012959:Socioeconomic Factors; D016019:Survival Analysis; D016896:Treatment Outcome; D014376:Tuberculosis / Q000188:drug therapy / Q000453:epidemiology / Q000401:mortality; D018088:Tuberculosis, Multidrug-Resistant / Q000188:drug therapy / Q000453:epidemiology / Q000401:mortality; D014481:United States / Q000453:epidemiology
chemical_list: D000995:Antitubercular Agents