August 24, 2009

TB antibiotic use linked to resistance

Common use of fluoroquinolones -- a class of antibiotics -- has been linked to an antibiotic-resistant tuberculosis, U.S. researchers said.

The retrospective case-control study, published in the American Journal of Respiratory and Critical Care Medicine, found increased use of this class of antibiotics may be undercutting their usefulness as the first-line defense against drug-resistant TB.

The researchers found a linear association between previous fluoroquinolone exposure and fluoroquinolone resistance.

For every additional 10 days of fluoroquinolone use, we found that patients had a 50 percent increase in the likelihood of having resistant TB, study leader Dr. Rose Devasia of Vanderbilt University in Nashville said in a statement.

The researchers found fluoroquinolone resistance highest among those undergoing fluoroquinolone treatment more than 60 days prior to TB diagnosis.

Using 2002-2006 data from the TennCare pharmacy database, the researchers determined fluoroquinolone use for the 12 months prior to TB diagnosis in 640 patients for whom stable cultures were available.

Age, race and other demographic factors were not significantly associated with resistance, but patients who had used fluoroquinolones within 12 months of diagnosis were almost five times as likely to have a fluoroquinolone-resistant strain of TB than those who had not used fluoroquinolones.