Relation between tetR and tetA expression in tetracycline resistant Escherichia coli. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Møller, Thea; Overgaard, Martin; Nielsen, Søren; Bortolaia, Valeria; Sommer, Morten; Guardabassi, Luca; Olsen, John
• Is Part Of: BMC microbiology. Volume 16:Issue 1(2016)
• Page Start: 1
• Page End: 8
• Publication Date: 2016-12
• Subjects: Antimicrobial resistance -- TetA -- TetR -- Tetracycline -- Tetracycline resistance; Microbiology -- Periodicals; 579.05
• DOI: 10.1186/s12866-016-0649-z
• Languages: English
• ISSNs: 1471-2180

Abstract

Abstract Background Tetracyclines are among the most used antibiotics in livestock worldwide. Resistance is widely disseminated inEscherichia coli, where it is generally mediated by tetracycline efflux pumps, such as TetA. Expression of tetracycline efflux pumps is tightly controlled by the repressor TetR, which has been shown to be tetracycline-responsive at sub-MIC tetracycline concentrations. The objective of this study was to investigate the effects of increasing tetracycline concentrations on the growth of TetA-producingE. coli, and to determine how expression oftetA andtetR related to each other in different growth phases in the presence of tetracycline. Results A tetracycline resistantE. coli strain containingtetA andtetR on the chromosome was constructed and cultured in the presence of increasing concentrations of tetracycline. Expression oftetR andtetA was measured at four time points in different growth phases by quantitative real-time PCR. The TetA-producingE. coli exhibited prolonged lag phase with increasing concentrations of tetracycline, while expression oftetA andtetR increased and decreased, respectively, with increasing tetracycline concentration. The levels oftetA andtetR mRNA varied depending on growth phase, resulting in a gradual decrease of thetetA /tetR ratio from approximately 4 in the lag phase to approximately 2 in the stationary phase. Conclusion This study shows that the expression oftetR andtetA is tetracycline concentration- and growth phase-dependent, contributing to improved understanding of the relationships betweenE. coli growth, tetracycline exposure and expression of tetracycline resistance.