Genetic basis of antibiotic resistance in pathogenic Acinetobacter species.

Antibiotic resistance in Acinetobacter spp., particularly Acinetobacter baumannii, is increasing rapidly. A. baumannii possesses two intrinsic β-lactamase genes, in addition to weak permeability and efflux systems, that together confer a natural reduced susceptibility to antibiotics. In addition, numerous acquired mechanisms of resistance have been identified in A. baumannii. The very high genetic plasticity of A. baumannii allows an accumulation of resistance determinants that give rise to multidrug resistance at an alarming rate. The role of novel genetic elements, such as resistance islands, in concentrating antibiotic resistance genes in A. baumannii requires detailed investigation in the near future.