Wednesday, August 12, 2009

Antibiotic Overuse Leads to Resistant Tuberculosis

Fluoroquinolones are one of the most commonly prescribed antibiotics in the U.S. and are used to fight a number of different infections such as pneumonia, and they include brand names Cipro, Floxin, Avelox and others. Often, they are prescribed for relatively minor issues, such as sinusitis. As you will see in many mentions on this blog, antibiotic overuse has led to many health concerns for our population.

The problem is that these same antibiotics are our first line of defense against TB (Tuberculosis) infections that show drug resistance. Now, research shows that the widespread general use of fluoroquinolones (for issues like sinusitis) may be creating a strain of fluoroquinolone-resistant TB. This general overuse of a common antibiotic may be undercutting the same drug's utility as our major defense against a terrible disease.

The results are published in the August 15 issue of the American Journal of Respiratory and Critical Care Medicine.

“While fluoroquinolone resistance in TB strains has been reported since the mid 1990’s, to our knowledge no one had investigated the direct causes of it,” said Dr. We wanted to determine whether and to what extent clinical practices were having an effect of creating that resistance,” said Rose A. Devasia, M.D., clinical instructor of Vanderbilt University.

To investigate the causes of the small but growing proportion of fluoroquinolone-resistant TB cases, Dr. Devasia and colleagues analyzed the records of every newly diagnosed patient with TB who was also enrolled in Tennessee’s Medicaid program, TennCare between January 2002 and December 2006. Using the TennCare pharmacy database, they were able to obtain information on the patients’ use of fluoroquinolone for the 12 months prior to their TB diagnosis. They used M. tuberculosis isolates taken from each patient to test for fluoroquinolone resistance in each case. Researchers found a linear association between previous fluoroquinolone exposure and fluoroquinolone resistance.

Overall, 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, and there was a linear association between length of fluoroquinolone use and fluoroquinolone resistance.

“For now, we all need to be more careful when considering the use of these drugs un the community setting and limit the use of prolonged or repeated courses of fluoroquinolones, or even avoid them altogether, in patients who are risk of having active TB,” they wrote in an accompanying editorial in the same issue of the journal.


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