Antibiotic resistance among gram-negative bacilli in US intensive care units: implications for fluoroquinolone use.

CONTEXT Previous surveillance studies have documented increasing rates of antimicrobial resistance in US intensive care units (ICUs) in the early 1990s. OBJECTIVES To assess national rates of antimicrobial resistance among gram-negative aerobic isolates recovered from ICU patients and to compare these rates to antimicrobial use. DESIGN AND SETTING Participating institutions, representing a total of 43 US states plus the District of Columbia, provided antibiotic susceptibility results for 35 790 nonduplicate gram-negative aerobic isolates recovered from ICU patients between 1994 and 2000. MAIN OUTCOME MEASURES Each institution tested approximately 100 consecutive gram-negative aerobic isolates recovered from ICU patients. Organisms were identified to the species level. Susceptibility tests were performed, and national fluoroquinolone consumption data were obtained. RESULTS The activity of most antimicrobial agents against gram-negative aerobic isolates showed an absolute decrease of 6% or less over the study period. The overall susceptibility to ciprofloxacin decreased steadily from 86% in 1994 to 76% in 2000 and was significantly associated with increased national use of fluoroquinolones. CONCLUSIONS This study documents the increasing incidence of ciprofloxacin resistance among gram-negative bacilli that has occurred coincident with increased use of fluoroquinolones. More judicious use of fluoroquinolones will be necessary to limit this downward trend.