Molecular mechanisms of biocide and antibiotic resistance in Acinetobacter baumannii

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）生存的能力而闻名。除了它令人印象深刻的适应恶劣环境的能力，A。鲍曼不动杆菌以其对目前使用的抗生素的高内在抗性而闻名。质子梯度依赖的外排系统属于耐药-结瘤-分裂（RND）家族，是导致曲霉内在耐药性的重要因素。鲍曼不动杆菌。三种不同的RND泵：AdeABC、AdeFGH和AdeIJK已在A.鲍曼不动杆菌。虽然这些泵的抗生素底物已经在文献中有很好的描述，但控制这些泵表达的调节机制还不是很清楚。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A.鲍曼不动杆菌仍然未知。在本申请中，我们提出寻求这两个问题的答案。我们已经分离出一个抗三氯生的A.过表达AdeFGH和AdeIJK泵的鲍曼不动杆菌。三氯生通过抑制脂肪酸生物合成酶FabI的作用靶向脂肪酸生物合成途径，我们观察到该突变体中FabI的表达也增加。在这个应用程序中，我们建议检查所观察到的RND泵和fabI的过表达是否与这种突变体有关，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。我们已经分析了AdeFGH和AdeIJK泵的已知调节子的序列，没有发现突变。这表明了其他调节因子在A.鲍曼不动杆菌。通过进行全基因组测序，我们已经确定了11个不同的基因在突变株含有突变相比，模式菌株。在本申请中，我们建议研究这些基因在RND泵和fabI表达中的作用。此外，我们还提出了两个新的RND泵（A1S_3217和A1S_0535）在A.鲍曼不动杆菌，其表达在三氯生抗性突变体中也改变。因此，拟议的研究计划不仅将为调节RND泵表达的机制提供新的见解，而且还将研究膜脂质与抗生素耐药性之间有趣的联系。

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.