Institut Pasteur, Unité des Agents Antibactériens, 28 Rue du Docteur Roux, 75724 Paris Cedex 15, France.
Antimicrob Agents Chemother. 2011 Mar;55(3):947-53. doi: 10.1128/AAC.01388-10. Epub 2010 Dec 20.
Among Acinetobacter spp., A. baumannii is the most frequently implicated in nosocomial infections, in particular in intensive care units. It was initially thought that multidrug resistance (MDR) in this species was due mainly to horizontal acquisition of resistance genes. However, it has recently become obvious that increased expression of chromosomal genes for efflux systems plays a major role in MDR. Among the five superfamilies of pumps, resistance-nodulation-division (RND) systems are the most prevalent in multiply resistant A. baumannii. RND pumps typically exhibit a wide substrate range that can include antibiotics, dyes, biocides, detergents, and antiseptics. Overexpression of AdeABC, secondary to mutations in the adeRS genes encoding a two-component regulatory system, constitutes a major mechanism of multiresistance in A. baumannii. AdeIJK, intrinsic to this species, is responsible for natural resistance, but since overexpression above a certain threshold is toxic for the host, its contribution to acquired resistance is minimal. The recently described AdeFGH, probably regulated by a LysR-type transcriptional regulator, also confers multidrug resistance when overexpressed. Non-RND efflux systems, such as CraA, AmvA, AbeM, and AbeS, have also been characterized for A. baumannii, as have AdeXYZ and AdeDE for other Acinetobacter spp. Finally, acquired narrow-spectrum efflux pumps, such as the major facilitator superfamily (MFS) members TetA, TetB, CmlA, and FloR and the small multidrug resistance (SMR) member QacE in Acinetobacter spp., have been detected and are mainly encoded by mobile genetic elements.
在不动杆菌属中，鲍曼不动杆菌最常引起医院感染，尤其是在重症监护病房。最初认为该物种的多药耐药性（MDR）主要是由于耐药基因的水平获得。然而，最近显然，染色体上的外排系统基因的表达增加在 MDR 中起主要作用。在五个超级家族的泵中，耐药-结节-分裂（RND）系统在多重耐药的鲍曼不动杆菌中最为普遍。RND 泵通常表现出广泛的底物范围，包括抗生素、染料、杀菌剂、清洁剂和防腐剂。AdeRS 基因编码的双组分调节系统突变导致 AdeABC 的过度表达，是鲍曼不动杆菌多耐药的主要机制。AdeIJK 是该物种的固有基因，负责天然耐药性，但由于超过一定阈值的过度表达对宿主有毒，因此其对获得性耐药性的贡献最小。最近描述的 AdeFGH，可能由 LysR 型转录调节因子调节，当过度表达时也赋予多药耐药性。非 RND 外排系统，如 CraA、AmvA、AbeM 和 AbeS，也已被鉴定为鲍曼不动杆菌，而 AdeXYZ 和 AdeDE 则用于其他不动杆菌属。最后，获得性窄谱外排泵，如主要易化因子超家族（MFS）成员 TetA、TetB、CmlA 和 FloR 以及 Acinetobacter spp. 中的小多药耐药（SMR）成员 QacE，已被检测到，主要由移动遗传元件编码。
