Effect of a program to reduce hospital ciprofloxacin use on nosocomial Pseudomonas aeruginosa susceptibility to quinolones and other antimicrobial agents

OBJECTIVE. We evaluated the effect of an antimicrobial management effort to decrease ciprofloxacin use on the antibiotic susceptibility of nosocomial Pseudomonas aeruginosa isolates. DESIGN. Retrospective, observational study. SETTING. Tertiary care teaching hospital with 731 beds. METHODS. The study was conducted between January 1, 2001, and December 31, 2007. Linear regression analyses and Student t tests were used to determine significant changes in drug use among patients and antimicrobial susceptibility patterns among nosocomial P. aeruginosa isolates during the 84-month period. RESULTS. Following implementation of a program to reduce oral and intravenous use of ciprofloxacin in 2005, there was a 56.6% reduction in ciprofloxacin use (P < .001). Significant reductions in the mean percentage of nosocomial P. aeruginosa isolates that were resistant to ciprofloxacin (from 45.0% to 35.2%; P < . 002) and the mean incidence of ciprofloxacin resistance ( from 0.77 to 0.67 isolates recovered per 1,000 patient-days; P = .03) were noted after implementation of this program. The total quantity of antipseudomonal antibiotics consumed decreased, but the use of certain antipseudomonal antibiotics (ie, cefepime and imipenem/meropenem) increased. Among nosocomial P. aeruginosa isolates, the prevalence of imipenem/meropenem resistance increased, whereas the prevalence of cefepime resistance did not. During the 84 months of the study, there was a significant association between ciprofloxacin use and the percentage of nosocomial P. aeruginosa isolates that were resistant to ciprofloxacin (rho = 0.47; P = .011), but there was no correlation between ciprofloxacin use and the incidence of ciprofloxacin resistance (rho = 0.21; P = .26). CONCLUSIONS. Major reductions in ciprofloxacin use were associated with small but significant improvements in the rate of ciprofloxacin susceptibility among nosocomial P. aeruginosa isolates. The impact of the program on other antipseudomonal agents was variable.