Relationship Between Rates of Antimicrobial Consumption and the Incidence of Antimicrobial Resistance inStaphylococcus aureusandPseudomonas aeruginosaIsolates From 47 French Hospitals

Abstract

Objective.To investigate relationships between rates of antimicrobial consumption and the incidence of antimicrobial resistance inStaphylococcus aureusandPseudomonas aeruginosaisolates from hospitals.Methods.We conducted an observational study that used retrospective data from 2002 and linear regression to model relationships. Hospitals were asked to collect data on consecutiveS. aureusandP. aeruginosaisolates, consumption rates for antibiotics (ie, anti-infectives for systemic use as defined by Anatomical Therapeutic Chemical class J01), and hospital characteristics, including infection control policies. Rates of methicillin resistance inS. aureusand rates of ceftazidime and ciprofloxacin resistance inP. aeruginosawere expressed as the percentage of isolates that were nonsusceptible (ie, either resistant or intermediately susceptible) and as the incidence of nonsuceptible isolates (ie, the number of nonsuceptible isolates recovered per 1,000 patient-days). The rate of antimicrobial consumption was expressed as the number of defined daily doses per 1,000 patient-days.Setting.Data were obtained from 47 French hospitals, and a total of 12,188S. aureusisolates and 6,370P. aeruginosaisolates were tested.Results.In the multivariate analysis, fewer antimicrobials showed a significant association between the consumption rate and the percentage of isolates that were resistant than an association between the consumption rate and the incidence of resistance. The overall rate of antibiotic consumption, not including the antibiotics used to treat methicillin-resistantS. aureusinfection, explained 13% of the variance between hospitals in the incidence of methicillin resistance amongS. aureusisolates. The incidence of methicillin resistance inS. aureusisolates increased with the use of ciprofloxacin and levofloxacin and with the percentage of the hospital's beds located in intensive care units (adjusted multivariate coefficient of determination [aR2], 0.30). ForP. aeruginosa, the incidence of ceftazidime resistance was greater in hospitals with higher consumption rates for ceftazidime, levofloxacin, and gentamicin (aR2, 0.37). The incidence of ciprofloxacin resistance increased with the use of fluoroquinolones and with the percentage of a hospital's beds located in intensive care (aR2, 0.28).Conclusions.A statistically significant relationship existed between the rate of fluoroquinolone use and the rate of antimicrobial resistance amongS. aureusandP. aeruginosaisolates. The incidence of resistant isolates showed a stronger association with the rate of antimicrobial use than did the percentage of isolates with resistance.