Acinetobacter baumannii: An Emerging Multidrug-resistant Threat

Thomas D Gootz; Andrea Marra


Expert Rev Anti Infect Ther. 2008;6(3):309-325. 

In This Article


While acinetobacters have been classified as opportunistic pathogens derived from environmental origins, this review emphasizes that clinical strains may encode important virulence factors and an extensive array of antibiotic-resistance genes. One can only expect that these genes will further disseminate globally among isolates of this species, since many are encoded on plasmids, transposons and class I and II integrons.[27,109,155,156,157,158,159] Furthermore, several examples have been cited in this review identifying MDR A. baumannii containing multiple resistance genes affecting activity against the same class of antibiotics. In order to appreciate the complicated mechanisms of antibiotic resistance in this species, one needs to consider the interplay of both intrinsic and acquired resistance mechanisms. A subtle, yet highly relevant, system for augmenting resistance levels can be illustrated by the existence of IS elements in the Acinetobacter genome, such as the ISAbc1 sequence that can insert itself into the 5'-end of existing resistance genes, providing them with strong promoter elements that upregulate resistance-gene expression. The combination of the intrinsic resistance determinants already present in A. baumannii, including carbapenemases, porin deletion, efflux and mutations in PBPs can contribute to clinically relevant carbapenem resistance.[160]


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