Temporal evolution of carbapenem-resistant Acinetobacter baumannii in Curitiba, southern Brazil

Background: In the last few years, carbapenem-resistant Acinetobacter baumannii isolates (CR-AB) have been identified worldwide. The first description of OXA-23-producing A baumannii in Brazil was from the city of Curitiba in 2003. The aim of the present study was to evaluate the persistence and dissemination of the first OXA-23-producing A baumannii clone isolated from patients in Hospital de Clinicas, Curitiba, Brazil. Methods: An antimicrobial susceptibility profile of the isolates was determined by the standard agar dilution method. Molecular detection of beta-lactamase genes was done by polymerase chain reaction. The clonal relationship of the isolates was analyzed by pulsed-field gel electrophoresis (PFGE). Epidemiologic and clinical features were evaluated as well. Results: Genotypic analysis of 172 CR-AB isolates by PFGE identified 3 distinct major PFGE clusters (A, B, and C, accounting for 36, 69, and 65 isolates, respectively). All isolates carried the bla(OXA-23)-like gene and were multidrug-resistant, but were susceptible to tigecycline and polymixin B. The mortality rate related to CR-AB infection was 45.4%, and ventilator-associated pneumonia and bloodstream infections were the most frequent clinical manifestations. Conclusions: The presence of 3 clones among the CR-AB isolates suggests that cross-transmission was the main mechanism responsible for dissemination of OXA-23 producers. PFGE pattern A was genotypically similar to that of the first OXA-23-producing A baumannii clone identified in Curitiba in 1999. This clone persisted in the same hospital until April 2004. The presence of the bla(OXA-23)-like gene was the main mechanism associated with carbapenem resistance among the isolates studied.