AdeIJK, a Resistance-Nodulation-Cell Division Pump Effluxing Multiple Antibiotics in Acinetobacter baumannii

Abstract

We have identified a second resistance-nodulation-cell division (RND)-type efflux pump, AdeIJK, in clinical isolate Acinetobacter baumannii BM4454. The adeI, adeJ, and adeK genes encode, respectively, the membrane fusion, RND, and outer membrane components of the pump. AdeJ belongs to the AcrB protein family (57% identity with AcrB from Escherichia coli). mRNA analysis by Northern blotting and reverse transcription-PCR indicated that the genes were cotranscribed. Overexpression of the cloned adeIJK operon was toxic in both E. coli and Acinetobacter. The adeIJK genes were detected in all of the 60 strains of A. baumannii tested. The two latter observations suggest that the AdeIJK complex might contribute to intrinsic but not to acquired antibiotic resistance in Acinetobacter. To characterize the substrate specificity of the pump, we have constructed derivatives of BM4454 in which adeIJK (strain BM4579), adeABC (strain BM4561), or both groups of genes (strain BM4652) were inactivated by deletion-insertion. Determination of the antibiotic susceptibility of these strains and of BM4652 and BM4579, in which the adeIJK operon was provided in trans, indicated that the AdeIJK pump contributes to resistance to ␤-lactams, chloramphenicol, tetracycline, erythromycin, lincosamides, fluoroquinolones, fusidic acid, novobiocin, rifampin, trimethoprim, acridine, safranin, pyronine, and sodium dodecyl sulfate. The chemical structure of these molecules suggests that amphiphilic compounds are the preferred substrates. The AdeABC and AdeIJK efflux systems contributed in a more than additive fashion to tigecycline resistance.

Prevalence of eight resistance-nodulation-division efflux pump genes in epidemiologically characterized Acinetobacter baumannii of worldwide origin

“…In Gram-negative bacteria, various mechanisms are associated with a multidrug resistance (MDR) phenotype, including enzymic drug inactivation/modification, target alteration, low membrane permeability and active efflux. Of these, increased expression of chromosomally encoded efflux pumps has been proposed as the first step in the development of a MDR phenotype (Piddock, 2006) and several reports have been published showing decreased susceptibility to multiple antibiotics due to the overexpression of normally cryptic efflux systems in A. baumannii (Coyne et al, 2010;Damier-Piolle et al, 2008;Higgins et al, 2010a;Magnet et al, 2001).…”

“…The proton gradient across the membrane serves as a driving force. To date, three RND efflux systems have been described in A. baumannii: AdeABC (Magnet et al, 2001), AdeFGH (Coyne et al, 2010) and AdeIJK (Damier-Piolle et al, 2008).…”

Structure and Function of the PiuA and PirA Siderophore-Drug Receptors from Pseudomonas aeruginosa and Acinetobacter baumannii

“…Besides its chromosomally encoded AmpC-type beta lactamase (20), A. baumannii frequently harbors class B and D carbapenemases (21) and extended-spectrum beta-lactamases (ESBL) of the PER, GES, and VEB types (22). RNDtype efflux systems, including AdeABC (23), AdeIJK (24), and AdeFGH (25), further contribute to the multidrug resistance phenotype of clinical isolates. A. baumannii harbors between 21 and 27 TonB-dependent receptors compared to 35 in P. aeruginosa (26).…”

Complete genome sequence analysis of the fish pathogen Flavobacterium columnare provides insights into antibiotic resistance and pathogenicity related genes

“…In this report, 286 genes were predicted as antibiotic resistance genes blasted with CARD. Among them, 32 genes were annotated as resistance-nodulationcell division (RND)-type efflux pumps (Table 5), which are tripartite complexes form a channel to facilitate drug export across the inner and outer membranes, driven by the proton motive force [66,67]. In particular, increased expression of adeABC and adeIJK, the two RND-type efflux pumps, has been associated with a multidrug resistance phenotype, specifically with the export of aminoglycosides [68,69].…”