Emergence of Resistance inPseudomonas aeruginosaandAcinetobacterSpecies After the Use of Antimicrobials for Burned Patients

Abstract

AbstractObjectives:To evaluate the emergence of resistance ofPseudomonas aeruginosaandAcinetobacterspecies to imipenem, ciprofloxacin, or both after the use of these drugs and to compare resistant with susceptible isolates by molecular typing.Design:Cohort study.Setting:Burn intensive care unit (ICU) with 4 beds in a tertiary-care university hospital.Methods:During 16 months, surveillance cultures were performed for all patients admitted to the ICU. Demographic information was obtained for each patient. Molecular typing was done by pulsed-field gel electrophoresis using restriction enzymes for 71 isolates ofP. aeruginosaandAcinetobacterspecies.Results:Thirty-four patients were admitted and 22 were colonized by susceptibleP. aeruginosaorAcinetobacterspecies before they used the antimicrobials. Nine (41%) of these patients had a resistant isolate after antimicrobial use: 5 had used imipenem alone, 1 had used ciprofloxacin, and 3 had used both drugs. The interval between isolation of the susceptible and resistant isolates ranged from 4 to 25 days, but was 10 or more days for 6 patients. Molecular typing revealed that susceptible and resistant isolates from each patient were different and that although there were no predominant clones among susceptible isolates, there was a predominant clone among resistant isolatesof P. aeruginosaandof Acinetobacter.Conclusions:Resistance was not due to the acquisition of resistance mechanisms by a previously susceptible strain, but rather to cross-transmission. Although various measures involving antimicrobial use have received great attention, it would seem that practices to prevent cross-transmission are more important in controlling resistance.