Molecular Epidemiology and Mechanisms of Carbapenem Resistance of Acinetobacter spp. in Asia and Oceania

Acinetobacter baumannii is emerging as a pathogen that is commonly involved in nosocomial infections. A. baumannii has exhibited the ability to develop multidrug resistance (MDR), including resistance to carbapenems, the last-line class of antibiotics to treat these infections. In particular, MDR A. baumannii International Clone (IC) 2 has disseminated worldwide causing substantial problems in hospitals, including in Asia and Oceania. The global spread of this clonal lineage emphasizes the importance of tracking molecular epidemiology to obtain greater understanding of the population dynamics of A. baumannii. Carbapenem resistance in A. baumannii occurs mainly as a result of acquisition of OXA-type carbapenemase genes, and to some extent by acquisition of metallo--lactamase genes. The acquisition of carbapenemase genes, particularly the bla(OXA-23), bla(OXA-40), and bla(OXA-58), by specific clonal lineages may be one of the attributes responsible for the relative homogeneity of the MDR A. baumannii population.