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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 2-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. The results revealed that the MICs of K12ΔacrB to the tested drugs except for gentamycin and amikacin decreased 2- to 16.75-folds compared with 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 with 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 with 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., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Japanese Biochemical Society. All rights reserved.)

In this paper, we studied the antibacterial effects of oregano essential oil (OEO) both alone, using a twofold dilution method, and combined with antibiotics, using a checkerboard microtitre assay, against extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli. The result indicated that multiple drug-resistant E. coli was very sensitive to OEO and polymycin; their minimal inhibitory concentration values are 0.5 microL mL(-1) and 0.8 microg mL(-1). The antibacterial effects of OEO in combination with kanamycin were independent against E. coli, with fractional inhibitory concentration (FIC) indices of 1.5. The antibacterial effects of OEO combined with amoxicillin, polymycin, and lincomycin showed an additive effect against E. coli, with FIC indices in the range of 0.625-0.750. The antibacterial effects of OEO in combination with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol displayed synergism against E. coli, with FIC indices ranging from 0.375 to 0.500. The combination of OEO with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol to treat infections caused by ESBL-producing E. coli may lower, to a great extent, the effective dose of these antibiotics and thus minimize the side effects of antibiotics. This is the first report on OEO against ESBL-producing E. coli.

The objective of this study was to evaluate the antibacterial mechanisms of phenolic acids as natural approaches against multi-drug resistant Escherichia coli (E. coli). For that purpose, five phenolic acids were combined with each other and 31 combinations were obtained in total. To select the most potent and effective combination, all of the obtained combinations were examined for minimum inhibitory concentration (MIC) and it was found that the compound phenolic acid (CPA) 19 (protocatechuic acid, hydrocinnamic acid, and chlorogenic acid at concentrations of 0.833, 0.208, and 1.677 mg/mL, respectively) showed better efficacy against E. coli compared to other combinations. Furthermore, based on tandem mass tag (TMT) proteomics, the treatment of CPA 19 significantly downregulated the proteins associated with resistance (Tsr, Tar, CheA, and CheW), OmpF, and FliC of multidrug-resistant E. coli. At the same time, we proved that CPA 19 improves the sensitivity of E. coli to antibiotics (ceftriaxone sodium, amoxicillin, fosfomycin, sulfamonomethoxine, gatifloxacin, lincomycin, florfenicol, cefotaxime sodium, and rifampicin), causes the flagellum to fall off, breaks the structure of the cell wall and cell membrane, and leads to macromolecules leaks from the cell. This evidence elaborated the potential therapeutic efficacy of CPA 19 and provided a significant contribution to the discovery of antibacterial agents. [ABSTRACT FROM AUTHOR]

In this paper, we studied the antibacterial effects of oregano essential oil (OEO) both alone, using a twofold dilution method, and combined with antibiotics, using a checkerboard microtitre assay, against extended-spectrum β-lactamase (ESBL)-producing Escherichia coli. The result indicated that multiple drug-resistant E. coli was very sensitive to OEO and polymycin; their minimal inhibitory concentration values are 0.5 μL mL−1 and 0.8 μg mL−1. The antibacterial effects of OEO in combination with kanamycin were independent against E. coli, with fractional inhibitory concentration (FIC) indices of 1.5. The antibacterial effects of OEO combined with amoxicillin, polymycin, and lincomycin showed an additive effect against E. coli, with FIC indices in the range of 0.625–0.750. The antibacterial effects of OEO in combination with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol displayed synergism against E. coli, with FIC indices ranging from 0.375 to 0.500. The combination of OEO with fluoroquinolones, doxycycline, lincomycin, and maquindox florfenicol to treat infections caused by ESBL-producing E. coli may lower, to a great extent, the effective dose of these antibiotics and thus minimize the side effects of antibiotics. This is the first report on OEO against ESBL-producing E. coli. [ABSTRACT FROM AUTHOR]