Molecular Basis of Antibiotic Resistance in Acinetobacter spp.
Kevin J. Towner
from: Acinetobacter Molecular Biology (Edited by: Ulrike Gerischer). Caister Academic Press, U.K. (2008)
Members of the genus Acinetobacter have the ability to develop resistance to new antibiotics extremely rapidly. Most multiresistant isolates of Acinetobacter spp. belong to the Acinetobacter baumannii complex, and many clinical isolates of A. baumannii are now resistant to all conventional antimicrobial agents, including carbapenems. Molecular studies have characterised most of the responsible genes and mechanisms of resistance to antibiotics found within the genus. Multidrug resistance typically results from the accumulation of multiple mutations and/or the acquisition of resistance genes from other bacterial genera, with the latter occurring by a variety of mechanisms, including the transfer of plasmids, transposons and integrons carrying clusters of genes encoding resistance to several unrelated families of antibiotics simultaneously. Whole-genome sequence analysis has identified the presence of resistance islands, apparently built through the successive insertion of broad host-range mobile genetic elements into an insertion hotspot on the A. baumannii chromosome. This ability to 'switch' its genetic structure may explain the unmatched speed at which A. baumannii captures resistance markers when under antibacterial selection pressure. Overall, the emergence of resistance among clinical isolates of A. baumannii appears to be a combined effect of gene acquisition, following lateral gene transfer, and clonal spread of multiresistant clones read more ...