Molecular mechanisms of biocide and antibiotic resistance in Acinetobacter baumannii

鲍曼不动杆菌杀菌剂和抗生素耐药性的分子机制

• 批准号: RGPIN-2015-05550
• 负责人: Kumar, Ayush
• 金额: $ 2.19万
• 依托单位: University of Manitoba
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613618
• 关键词: Molecular; mechanisms; biocide; antibiotic; resistance

Acinetobacter baumannii is a Gram-negative pathogen that is known for its ability to survive under harsh environmental conditions, including hospital settings. In addition to its impressive ability to adapt to inhospitable environments, A. baumannii is known for its high intrinsic resistance to antibiotics currently in use. Proton gradient-dependent efflux systems belonging to the Resistance-Nodulation-Division (RND) family are important factors contributing to the intrinsic antibiotic resistance of A. baumannii. Three different RND pumps: AdeABC, AdeFGH, and AdeIJK, have been characterized in A. baumannii. While the antibiotic substrates of these pumps have been well described in the literature, regulatory mechanisms that control the expression of these pumps are not very well understood. In addition, while there is a general consensus that the efflux of antibiotics is not their primary role, physiological function(s) of these pumps in A. baumannii remain unknown. In this application, we propose to seek answers to these two questions. We have isolated a triclosan resistant mutant of A. baumannii that overexpresses the AdeFGH and AdeIJK pumps. Triclosan targets the fatty acid biosynthesis pathway by inhibiting the action of fatty acid biosynthesis enzyme FabI, and we observed that the expression of fabI is increased in this mutant as well. In this application we propose to examine if the observed overexpression of RND pumps and fabI is linked in this mutant, and also if perturbations in fatty acid biosynthesis can lead to the overexpression of RND efflux pumps. We have analyzed the sequences of known regulators of both the AdeFGH and AdeIJK pumps and have found no mutations. This suggests the role of other regulators that control the expression of the AdeFGH and AdeIJK RND pumps in A. baumannii. By conducting whole genome sequencing, we have identified eleven different genes in the mutant strain that contain mutations when compared to a type strain. In this application we propose to study the role of these genes in the expression of RND pumps as well as fabI. In addition, we also propose to characterize two novel RND pumps (A1S_3217 and A1S_0535) in A. baumannii, whose expression was also altered in the triclosan-resistant mutant. The proposed research program will therefore not only provide new insights into the mechanisms that regulate the expression of RND pumps, but will also investigate the intriguing link between membrane lipids and antibiotic resistance.

鲍曼不动杆菌是一种革兰氏阴性病原体，以其在恶劣环境条件下（包括医院环境）存活的能力而闻名。除了具有令人印象深刻的适应恶劣环境的能力外，鲍曼不动杆菌还因其对目前使用的抗生素具有高度的内在耐药性而闻名。属于耐药-结瘤-分裂（RND）家族的质子梯度依赖外排系统是鲍曼不动杆菌固有抗生素耐药的重要因素。三种不同的RND泵：AdeABC， AdeFGH和AdeIJK，已经在鲍曼不动杆菌中被表征。虽然这些泵的抗生素底物已经在文献中得到了很好的描述，但控制这些泵表达的调控机制还不是很清楚。此外，虽然普遍认为抗生素的外排不是它们的主要作用，但这些泵在鲍曼不动杆菌中的生理功能仍不清楚。在本次申请中，我们拟寻求这两个问题的答案。我们已经分离出一种耐三氯生的鲍曼不动杆菌突变体，它过表达AdeFGH和AdeIJK泵。三氯生通过抑制脂肪酸生物合成酶FabI的作用来靶向脂肪酸生物合成途径，我们观察到在该突变体中FabI的表达也增加了。在这个应用中，我们建议检查观察到的RND泵和fabI的过表达是否在这个突变体中有联系，以及脂肪酸生物合成的扰动是否会导致RND外排泵的过表达。我们分析了已知的AdeFGH和AdeIJK泵的调控序列，没有发现突变。这提示了鲍曼不动杆菌中控制AdeFGH和AdeIJK RND泵表达的其他调节因子的作用。通过进行全基因组测序，我们在突变菌株中发现了11个不同的基因，与型菌株相比，这些基因包含突变。在这个应用中，我们建议研究这些基因在RND泵和fabI表达中的作用。此外，我们还提出表征鲍曼不动杆菌中两个新的RND泵（A1S_3217和A1S_0535），它们的表达在三氯生抗性突变体中也发生了改变。因此，拟议的研究计划不仅将为调控RND泵表达的机制提供新的见解，而且还将研究膜脂和抗生素耐药性之间的有趣联系。