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Prior use of fluoroquinolone antibiotics boosts the risk of fluoroquinolone-resistant infections

Fluoroquinolines (FQs) are a class of antibiotics with few side effects that are effective against a broad spectrum of bacteria. Widespread use has resulted in an increasing number of FQ-resistant bacterial infections in both hospitals and long-term care medical facilities, according to two studies supported by the Agency for Healthcare Research and Quality (HS10399). Continued widespread FQ use may limit the utility of this broad-spectrum, oral antibiotic class, according to researchers at the University of Pennsylvania Center for Education and Research on Therapeutics.

In the first study, researchers found that long-term care patients who had used FQ antibiotics in the past were at greater risk of developing FQ-resistant Escherichia coli urinary tract infections (UTIs). While prior FQ exposure is a well-established risk factor for FQ-resistant infection in the acute care setting, this study is the first to extend these findings to the long-term care setting. A study of inpatients in the Philadelphia Veterans Administration Nursing Home Care Unit between 2000 and 2004 found that of 102 men with at least 1 urine culture positive for E. coli during the study period, 45 percent had FQ-resistant E. coli. Of these patients, 33 met clinical criteria for FQ-resistant E. coli infections and were designated as cases. They were compared with 132 controls. Prior FQ use and urinary catheterization (a well-known risk factor for UTIs) were found to be strong risk factors for the development of an FQ-resistant E. coli UTI. However, neither duration of use nor number of courses of FQ therapy were significant risk factors.

In the second study, the researchers studied all Pseudomonas aeruginosa isolates at one hospital laboratory between 1991 and 2000 to examine trends in the prevalence of FQ-resistant P. aeruginosa (FQRPA). Annual hospital prevalence of FQRPA increased from 15 percent in 1991 to 41 percent in 2000. In a separate case, a control study of isolates identified in 1999 and 2000, FQRPA was associated with prior FQ use. The researchers note that P. aeruginosa infections have been associated with considerable morbidity and mortality, and that FQs are the only oral therapy available for these infections.

For more details, see "Fluoroquinolone-resistant Escherichia coli in the long-term care setting," by Alana E. Cohen, M.D., Ebbing Lautenbach, M.D., M.P.H., M.S.C.E., Knashawn H. Morales, Sc.D., and Darren R. Linkin, M.D., M.S.C.E., in the November 2006 American Journal of Medicine 119(11), pp. 958-963; and "Fluoroquinolone-resistant Pseudomonas aeruginosa: Assessment of risk factors and clinical impact," by Leanne B. Gasink, M.D., Neil O. Fishman, M.D., Mark G. Weiner, M.D., and others, in the June 2006 American Journal of Medicine 119(6), pp. 526-532.

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