Institute for Medical Microbiology, Immunology and Hygiene, Faculty of Medicine and University Hospital Colognegrid.411097.a, University of Colognegrid.6190.e, Cologne, Germany.
German Center for Infection Research (DZIF), Partner Site Bonn-Cologne, Cologne, Germany.
mSphere. 2021 Dec 22;6(6):e0070921. doi: 10.1128/msphere.00709-21. Epub 2021 Nov 24.
In Acinetobacter baumannii, resistance-nodulation-cell division (RND)-type efflux is a resistance mechanism of great importance since it contributes to reduced susceptibility to multiple antimicrobial compounds. Some mutations within the genes encoding the two-component regulatory system AdeRS appear to play a major role in increased expression of the RND efflux pump AdeABC and, consequently, in reduced antimicrobial susceptibility, as they are commonly observed in multidrug-resistant (MDR) A. baumannii. In the present study, the impact of frequently identified amino acid substitutions, namely, D21V and D26N in AdeR and T156M in AdeS, on expression, efflux activity, and antimicrobial susceptibility was investigated. Reverse transcription-quantitative PCR (qRT-PCR) studies revealed significantly increased expression caused by D26N (AdeR) and T156M (AdeS). In addition, accumulation assays have shown that these mutations induce increased efflux activity. Subsequently, antimicrobial susceptibility testing via agar dilution and broth microdilution confirmed the importance of these substitutions for the MDR phenotype, as the MICs for various antimicrobials of different classes were increased. In contrast, the amino acid substitution D21V in AdeR did not lead to increased expression and did not reduce antimicrobial susceptibility. This study demonstrates the impact of the D26N (AdeR) and T156M (AdeS) amino acid substitutions, highlighting that these regulators represent promising targets for interfering with efflux activity to restore antimicrobial susceptibility. The active efflux of antimicrobials by bacteria can lead to antimicrobial resistance and persistence and can affect multiple different classes of antimicrobials. Efflux pumps are tightly regulated, and their overexpression can be mediated by changes in their regulators. Identifying these changes is one step in the direction of resistance prediction, but it also opens the possibility of targeting efflux pump regulation as a strategy to overcome antimicrobial resistance. Here, we have investigated commonly found changes in the regulators of the main efflux pumps in Acinetobacter baumannii.
在鲍曼不动杆菌中，耐药-结节-分裂（RND）型外排是一种非常重要的耐药机制，因为它导致对抗生素化合物的敏感性降低。编码双组分调节系统 AdeRS 的基因中的一些突变似乎在增加 RND 外排泵 AdeABC 的表达方面发挥主要作用，并且因此导致抗生素敏感性降低，因为它们在多药耐药（MDR）A.baumannii 中经常观察到。在本研究中，研究了经常发现的氨基酸取代的影响，即 AdeR 中的 D21V 和 D26N 以及 AdeS 中的 T156M，对表达、外排活性和抗生素敏感性的影响。逆转录定量 PCR（qRT-PCR）研究表明，D26N（AdeR）和 T156M（AdeS）引起的表达显著增加。此外，积累测定表明这些突变诱导增加的外排活性。随后，通过琼脂稀释和肉汤微量稀释进行的抗生素敏感性测试证实了这些取代对于 MDR 表型的重要性，因为不同类别的各种抗生素的 MIC 增加。相比之下，AdeR 中的氨基酸取代 D21V 并未导致表达增加，也不会降低抗生素敏感性。本研究证明了 D26N（AdeR）和 T156M（AdeS）氨基酸取代的影响，强调这些调节剂代表了干扰外排活性以恢复抗生素敏感性的有前途的靶标。 细菌主动排出抗生素会导致抗生素耐药性和持久性，并可能影响多种不同类别的抗生素。外排泵受到严格调节，其过度表达可以通过其调节剂的变化介导。鉴定这些变化是朝着耐药性预测方向迈出的一步，但它也为靶向外排泵调节作为克服抗生素耐药性的策略开辟了可能性。在这里，我们研究了鲍曼不动杆菌主要外排泵调节剂中常见的变化。
