The two-component system BaeSR participates in antibiotics resistance of Escherichia coli. To know whether the outer membrane proteins involve in the antibiotics resistance mediated by BaeSR, deletion of acrB was constructed and the recombined plasmid p-baeR was introduced into E. coli K12 and K12△acrB. Minimum Inhibitory concentrations (MICs) of antibacterial agents were determined by two-fold broth micro-dilution method. Gene expressions related with major outer membrane proteins and multidrug efflux pump-related genes were determined by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The results revealed that the MICs of K12ΔacrB to the tested drugs except for gentamycin and amikacin decreased 2- to 16.75-folds compared to those of K12. When BaeR was overexpressed, the MICs of K12ΔacrB/p-baeR to ceftiofur and cefotaxime increased 2.5- and 2-fold, respectively, compared to their corresponding that of K12△acrB. At the same time, the expression levels of ompC, ompF, ompW, ompA and ompX showed significant reduction in K12ΔacrB/p-baeR as compared to K12△acrB. Moreover, the expression levels of ompR, marA, rob and tolC also significantly decreased in K12ΔacrB/p-baeR. These findings indicated that BaeR overproduction can decrease cephalosporins susceptibility in acrB-free E. coli by decreasing the expression level of outer membrane proteins.

中文翻译：

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BaeR 通过调节大肠杆菌外膜蛋白的表达水平参与头孢菌素敏感性研究。

双组分系统 BaeSR 参与了大肠杆菌的抗生素耐药性。为了了解外膜蛋白是否参与BaeSR介导的抗生素耐药性，构建了acrB的缺失，并将重组质粒p -baeR引入大肠杆菌K12和K12△ acrB。抗菌剂的最低抑菌浓度（MICs）通过两倍肉汤微量稀释法测定。通过实时定量逆转录聚合酶链反应（qRT-PCR）确定与主要外膜蛋白和多药外排泵相关基因相关的基因表达。结果表明，K12ΔacrB 的MIC与K12相比，除庆大霉素和阿米卡星外的受试药物减少了2至16.75倍。当BaeR过表达时，K12ΔacrB /p - baeR对头孢噻呋和头孢噻肟的 MIC 分别比其对应的 K12ΔacrB 增加 2.5 倍和 2倍。同时，与K12ΔacrB相比，ompC 、 ompF 、 ompW 、 ompA和ompX的表达水平在K12ΔacrB /p -baeR中显着降低。此外， ompR、marA、rob的表达水平K12ΔacrB /p -baeR中的tolC也显着下降。这些发现表明，BaeR 过度生产可以通过降低外膜蛋白的表达水平来降低无 acrB 大肠杆菌中头孢菌素的敏感性。