Antibiotic misuse creates resistant TB.

Widespread, general use of a common antibiotic might be creating a strain of fluoroquinolone-resistant tuberculosis, according to a study in the Aug. 15 American Journal of Respiratory and Critical Care Medicine.

Researchers analyzed records of every newly diagnosed patient with culture-confirmed TB who was also enrolled in Tennessee's Medicaid Program, known as TennCare, between January 2002 and December 2006. Using the TennCare pharmacy database, they obtained information on patients' use of fluoroquinolone for the 12 months prior to a TB diagnosis.

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Overall, patients who had used fluoroquinolone 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 the antibiotics. And those who had undergone shorter treatment of less than 10 days had a 1.6 percent rate of resistance, but for every additional 10 days of fluoroquinolone use the study's authors found a 50 percent increase in the likelihood of having resistant TB.

Fluoroquinolones are the most commonly prescribed antibiotics in the United States and are used to treat a variety of infections, including sinusitis and pneumonia.