title: Fluoroquinolone susceptibility among Mycobacterium tuberculosis isolates from the United States and Canada.
abstract: BACKGROUND
  There is increasing interest in the possible role of new fluoroquinolone antibiotics for treatment of tuberculosis, but widespread use of fluoroquinolones for treatment of other bacterial infections may select for resistant strains of Mycobacterium tuberculosis.
  
  
  METHODS
  We evaluated fluoroquinolone susceptibility using the proportion method (critical ciprofloxacin concentration for susceptibility testing, 2.0 mu g/mL) in isolates obtained from patients enrolled in Tuberculosis Trial Consortium clinical trials during the period of 1995-2001 and in a referral sample of isolates sent to the Centers for Disease Control and Prevention (Atlanta, GA) during the period of 1996-2000 for additional testing, often because of drug resistance.
  
  
  RESULTS
  Of the 1373 isolates from the clinical trials, 1324 (96%) were susceptible to isoniazid and rifampin; 2 (0.15%) of these isolates were also resistant to ciprofloxacin. Of the 1852 isolates from the referral sample, 603 (32.6%) were resistant to isoniazid and rifampin (i.e., multidrug resistant), 849 (45.7%) were resistant to >or=1 first-line drug but were not resistant to both isoniazid and rifampin, and 400 (21.6%) were susceptible to all first-line agents. Ciprofloxacin resistance was found in 33 (1.8%) of the referral-sample isolates. Most ciprofloxacin-resistant isolates (25 [75.8%]) were resistant to isoniazid and rifampin.
  
  
  CONCLUSIONS
  Despite widespread use of fluoroquinolones for treatment of common bacterial infections, resistance among clinical isolates of M. tuberculosis in the United States and Canada remains rare, occurring primarily among multidrug-resistant strains.
authors.affiliation: Division of Tuberculosis Elimination, Centers for Disease Control and Prevention, Atlanta, GA, USA.
authors.forename: Lorna
authors.initials: L
authors.lastname: Bozeman
authors.forename: William
authors.initials: W
authors.lastname: Burman
authors.forename: Beverly
authors.initials: B
authors.lastname: Metchock
authors.forename: Lauren
authors.initials: L
authors.lastname: Welch
authors.forename: Marc
authors.initials: M
authors.lastname: Weiner
mesh_terms: D000995:Antitubercular Agents / Q000494:pharmacology*; D002170:Canada / Q000453:epidemiology; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D008297:Male; D009169:Mycobacterium tuberculosis / Q000187:drug effects*; D014376:Tuberculosis / Q000453:epidemiology / Q000382:microbiology; D014481:United States / Q000453:epidemiology
chemical_list: D000995:Antitubercular Agents; D024841:Fluoroquinolones