WASHINGTON — Fluoroquinolone resistance rose significantly over an 8-year period in hospitalized adults aged 65 years and older with gram-negative bacterial infections.
The safety and bioavailability of fluoroquinolones (FQs) have made them a popular choice for treating infections—especially urinary tract and intra-abdominal infections—in older adults. But increased fluoroquinolone resistance in gram-negative bacteria may have a significant impact on the use of these agents in this population, wrote Jon P. Furuno, Ph.D., of the University of Maryland, Baltimore, and his colleagues in a poster presented at the annual meeting of the American Geriatrics Society.
They collected microbiology data from all cultures that tested positive for gram-negative bacteria in patients aged 65 years and older who were admitted to the University of Maryland Medical Center between January 1998 and December 2005.
During that period, they analyzed a total of 1,839 Escherichia coli, 554 Proteus mirabilis, 1,044 Pseudomonas aeruginosa, 1,068 Klebsiella, and 480 Enterobacter cloacae isolates.
FQ resistance increased significantly across all species, from 8% in 1998 to almost 27% in 2005. But resistance varied by species and within years. Species-specific significant increases in the percentage of resistant isolates were observed from 1998 to 2005 for E. coli (3% vs. 31%), P. mirabilis (7 % vs. 39%), and Klebsiella (1.7% vs. 9.3%). Resistance rates in P. aeruginosa and E. cloacae increased from 1998 to 2005, but the differences were not statistically significant.
The researchers defined FQ resistance as resistance to all FQ drugs against which the isolates were tested, including ciprofloxacin, levofloxacin, and gatifloxacin.
They urged that prescribers consider the evidence of rising FQ resistance when choosing antibiotics for hospitalized older adults, although they conceded that more data are needed to determine the impact on treatment failure and subsequent outcomes in this population.
The study was supported in part by funding from the National Institutes of Health, the Centers for Disease Control and Prevention, and the Infectious Diseases Society of America. Dr. Furuno did not disclose any financial conflicts.