Damier-Piolle Laurence, Magnet Sophie, Brémont Sylvie, Lambert Thierry, Courvalin Patrice
Unité des Agents Antibactériens, Institut Pasteur, 25, rue du Docteur Roux, 75724 Paris Cedex 15, France.
Antimicrob Agents Chemother. 2008 Feb;52(2):557-62. doi: 10.1128/AAC.00732-07. Epub 2007 Dec 17.
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 beta-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.
我们在临床分离株鲍曼不动杆菌BM4454中鉴定出了第二种耐药-固氮-细胞分裂（RND）型外排泵AdeIJK。adeI、adeJ和adeK基因分别编码该泵的膜融合蛋白、RND蛋白和外膜蛋白。AdeJ属于AcrB蛋白家族（与大肠杆菌的AcrB有57%的同源性）。通过Northern印迹和逆转录PCR进行的mRNA分析表明这些基因是共转录的。克隆的adeIJK操纵子的过表达在大肠杆菌和不动杆菌中均具有毒性。在所检测的60株鲍曼不动杆菌中均检测到了adeIJK基因。后两个观察结果表明，AdeIJK复合物可能对不动杆菌的固有抗生素耐药性有贡献，但对获得性抗生素耐药性无贡献。为了表征该泵的底物特异性，我们构建了BM4454的衍生物，其中adeIJK（菌株BM4579）、adeABC（菌株BM4561）或两组基因（菌株BM4652）通过缺失插入失活。对这些菌株以及adeIJK操纵子通过反式提供的BM4652和BM4579的抗生素敏感性测定表明，AdeIJK泵有助于对β-内酰胺类、氯霉素、四环素、红霉素、林可酰胺类、氟喹诺酮类、夫西地酸、新生霉素、利福平、甲氧苄啶、吖啶、番红、派洛宁和十二烷基硫酸钠产生耐药性。这些分子的化学结构表明两亲性化合物是其首选底物。AdeABC和AdeIJK外排系统对替加环素耐药性的贡献呈超相加方式。
