blaOXA-51-type β-lactamase genes are ubiquitous and vary within a strain in Acinetobacter baumannii

We investigated the spread of blaOXA-51-type β-lactamase genes in 200 Acinetobacter spp. clinical strains isolated in Argentina from 1982 to 2005. blaOXA-51-type genes were present in all Acinetobacter baumannii isolates tested (n = 194), whereas they were not detected in two Acinetobacter haemolyticus, two genomic species 10 or two Acinetobacter lwoffii isolates. The blaOXA-51-type alleles varied within a strain and were found in six different A. baumannii pulsed-field gel electrophoresis clones that were susceptible or resistant to imipenem, suggesting a controversial role in imipenem resistance. Our findings agree with previous reports showing that blaOXA-51-type genes are naturally harboured by A. baumannii isolates from various geographical origins and support the presence of a direct reservoir of β-lactam resistance genes within the nosocomial environment.