Fluoroquinolone Susceptibility among Mycobacterium tuberculosis Isolates from the United States and Canada

• Published in: Clinical infectious diseases 2005-02, Vol.40 (3), p.386-391
• Main Authors: Bozeman, Lorna, Burman, William, Metchock, Beverly, Welch, Lauren, Weiner, Marc
• Format: Article
• Language: English
• Subjects: Antibacterial agents; Antibiotics; Antibiotics. Antiinfectious agents. Antiparasitic agents; Antitubercular Agents - pharmacology; Bacteria; Bacterial diseases; Biological and medical sciences; Canada - epidemiology; Clinical trials; Drug resistance; Drug Resistance, Multiple, Bacterial; Experimentation; Female; Fluoroquinolones; Fluoroquinolones - pharmacology; Fungal diseases; Genetic mutation; Human bacterial diseases; Humans; Infections; Infectious diseases; Major Articles; Male; Medical sciences; Medical treatment; Multidrug resistant tuberculosis; Mycobacterium tuberculosis; Mycobacterium tuberculosis - drug effects; Pharmacology. Drug treatments; Preventive medicine; Pulmonary tuberculosis; Tuberculosis; Tuberculosis - epidemiology; Tuberculosis - microbiology; Tuberculosis and atypical mycobacterial infections; United States - epidemiology
• ISSN: 1058-4838; 1537-6591
• DOI: 10.1086/427292

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 µg/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 ⩾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.