Rationale: Fluoroquinolones are the most commonly prescribed antibiotic class in the United States. They have the potential to become first-line antituberculosis therapy, but the effect of fluoroquinolone use on fluoroquinolone resistance in Mycobacterium tuberculosis is not well characterized.
Objectives: To determine the prevalence of and risk factors for fluoroquinolone-resistant tuberculosis in a large United States population.
Methods: We identified all people with culture-confirmed tuberculosis enrolled in TennCare (Medicaid) and reported to the Tennessee Department of Health from January 2002 to December 2006. People with fluoroquinolone-resistant M. tuberculosis isolates (cases) were compared with those with susceptible isolates (control subjects). Fluoroquinolone resistance was determined by agar proportion using ofloxacin 2 microg/ml. Outpatient fluoroquinolone exposure in the 12 months before tuberculosis diagnosis was ascertained from TennCare pharmacy data.
Measurements and main results: Of 640 study patients, 116 (18%) had fluoroquinolone exposure in the 12 months before diagnosis, and 16 (2.5%; 95% confidence interval [CI], 1.4-4.0%) M. tuberculosis isolates were fluoroquinolone resistant. Among the 54 patients with more than 10 days of fluoroquinolone exposure, 7 (13%) had fluoroquinolone resistance. In multivariable logistic regression analyses using propensity score to control for age, sex, race, HIV serostatus, and site of disease, more than 10 days of fluoroquinolone exposure before tuberculosis diagnosis was associated with fluoroquinolone resistance (odds ratio 7.0; 95% CI, 2.3-20.6; P = 0.001). Fluoroquinolone exposure for more than 10 days that occurred more than 60 days before tuberculosis diagnosis was associated with the highest risk of resistance (20.8%; odds ratio 17.0; 95% CI, 5.1-56.8; P < 0.001 compared with no exposure).
Conclusions: Overall, fluoroquinolone resistance was relatively low. However, receipt of fluoroquinolones for more than 10 days, particularly more than 60 days before tuberculosis diagnosis, was associated with a high risk of fluoroquinolone-resistant tuberculosis.