Data_Sheet_1_Quorum Sensing as a Target for Controlling Surface Associated Motility and Biofilm Formation in Acinetobacter baumannii ATCC® 17978TM.PDF

The important nosocomial pathogen Acinetobacter baumannii presents a quorum sensing (QS) system (abaI/abaR) mediated by acyl-homoserine-lactones (AHLs) and several quorum quenching (QQ) enzymes. However, the roles of this complex network in the control of the expression of important virulence-related phenotypes such as surface-associated motility and biofilm formation is not clear. Therefore, the effect of the mutation of the AHL synthase AbaI, and the exogenous addition of the QQ enzyme Aii20J on surface-associated motility and biofilm formation by A. baumannii ATCC® 17978TM was studied in detail. The effect of the enzyme on biofilm formation by several multidrug-resistant A. baumannii clinical isolates differing in their motility pattern was also tested. We provide evidence that a functional QS system is required for surface-associated motility and robust biofilm formation in A. baumannii ATCC® 17978TM. Important differences were found with the well-studied strain A. nosocomialis M2 regarding the relevance of the QS system depending on environmental conditions The in vitro biofilm-formation capacity of A. baumannii clinical strains was highly variable and was not related to the antibiotic resistance or surface-associated motility profiles. A high variability was also found in the sensitivity of the clinical strains to the action of the QQ enzyme, revealing important differences in virulence regulation between A. baumannii isolates and confirming that studies restricted to a single strain are not representative for the development of novel antimicrobial strategies. Extracellular DNA emerges as a key component of the extracellular matrix in A. baumannii biofilms since the combined action of the QQ enzyme Aii20J and DNase reduced biofilm formation in all tested strains. Results demonstrate that QQ strategies in combination with other enzymatic treatments such as DNase could represent an alternative approach for the prevention of A. baumannii colonization and survival on surfaces and the prevention and treatment of infections caused by this pathogen.

重要的医院获得性病原体鲍曼不动杆菌（Acinetobacter baumannii）拥有一套由酰基高丝氨酸内酯（acyl-homoserine-lactones, AHLs）介导的群体感应（quorum sensing, QS）系统（abaI/abaR）以及多种群体淬灭（quorum quenching, QQ）酶。然而，该复杂调控网络在调控诸如表面相关运动性、生物被膜形成等重要毒力相关表型的表达过程中所扮演的具体角色仍未阐明。因此，本研究详细探究了AHL合酶AbaI的突变，以及外源添加群体淬灭酶Aii20J对鲍曼不动杆菌ATCC® 17978TM的表面相关运动性与生物被膜形成的影响。此外，本研究还检测了该酶对多株运动模式各异的多重耐药鲍曼不动杆菌临床分离株生物被膜形成的作用。本研究证实，功能完整的QS系统是鲍曼不动杆菌ATCC® 17978TM实现表面相关运动性与成熟生物被膜形成的必要条件。相较于研究较为透彻的诺科姆不动杆菌M2菌株（A. nosocomialis M2），本研究发现QS系统的调控效应会因环境条件不同而存在显著差异。鲍曼不动杆菌临床菌株的体外生物被膜形成能力呈现高度异质性，且与其抗生素耐药性或表面相关运动性特征并无关联。临床菌株对QQ酶的敏感性同样存在显著差异，这揭示了不同鲍曼不动杆菌分离株在毒力调控层面的重要区别，同时证实仅针对单株菌株的研究无法代表新型抗菌策略开发的普适性结论。细胞外DNA是鲍曼不动杆菌生物被膜细胞外基质的关键组成成分：联合使用QQ酶Aii20J与脱氧核糖核酸酶（deoxyribonuclease, DNase）可显著降低所有受试菌株的生物被膜形成水平。研究结果表明，将QQ策略与脱氧核糖核酸酶等其他酶学疗法联用，有望成为预防鲍曼不动杆菌在物体表面定植与存活，以及防治该病原体引发感染的新型替代方案。