Fig 1.
Schematic representation of mechanisms involved in antibiotic resistance of A.
baumannii. (A) indicates the acquisition of a plasmid that carries antibiotic resistance genes; (B) is an schematic of antibiotic resistance gene acquisition via insertion of a composite Tn onto the chromosome (marked “Chr”); (C) indicates the insertion of ISAba1 (IS) upstream of the chromosomal ampC gene, providing the gene a strong promoter and therefore enhancing expression level leading to resistance to third-generation cephalosporins; (D) is a schematic of acquiring a resistance region (GI, T, etc.) via its flanking sequences—of any length—via homologous recombination [25]. ARG, antibiotic resistance gene; GI, genomic island; IS, insertion sequence; Tn, transposon.
Fig 2.
Intrinsic resistance mechanisms.
(A) AdeABC pump (of the RND family) is the most important for efflux-mediated drug resistance in A. baumannii. (B) Regulation of AdeABC is mediated by AdeRS, where ISs and single point mutations can disrupt these genes and result in overexpression. IM, inner membrane; IS, insertion sequence; LOS, lipooligosaccaride; OM, outer membrane; RND, resistance-nodulation-division.