Relation between tetR and tetA expression in tetracycline resistant Escherichia coli

BACKGROUND: Tetracyclines are among the most used antibiotics in livestock worldwide. Resistance is widely disseminated in Escherichia 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-producing E. coli, and to determine how expression of tetA and tetR related to each other in different growth phases in the presence of tetracycline. RESULTS: A tetracycline resistant E. coli strain containing tetA and tetR on the chromosome was constructed and cultured in the presence of increasing concentrations of tetracycline. Expression of tetR and tetA was measured at four time points in different growth phases by quantitative real-time PCR. The TetA-producing E. coli exhibited prolonged lag phase with increasing concentrations of tetracycline, while expression of tetA and tetR increased and decreased, respectively, with increasing tetracycline concentration. The levels of tetA and tetR mRNA varied depending on growth phase, resulting in a gradual decrease of the tetA/tetR ratio from approximately 4 in the lag phase to approximately 2 in the stationary phase. CONCLUSION: This study shows that the expression of tetR and tetA is tetracycline concentration- and growth phase-dependent, contributing to improved understanding of the relationships between E. coli growth, tetracycline exposure and expression of tetracycline resistance. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12866-016-0649-z) contains supplementary material, which is available to authorized users

Galectin-3 and fibulin-1 in systolic heart failure:relation to glucose metabolism and left ventricular contractile reserve

Abstract Background Heart failure (HF) patients with diabetes (DM) have an adverse prognosis and reduced functional capacity, which could be associated with cardiac fibrosis, increased chamber stiffness and reduced left ventricular (LV) contractile reserve. Galectin-3 (Gal-3) and fibulin-1 are circulating biomarkers potentially reflecting cardiac fibrosis. We hypothesize that plasma levels of Gal-3 and fibulin-1 are elevated in HF patients with DM and are associated with reduced LV contractile reserve in these patients. Methods A total of 155 patients with HF with reduced ejection fraction underwent a low-dose dobutamine echocardiography and blood sampling for biomarker measurements. Patients were classified according to history of DM and an oral glucose tolerance test (OGTT) as: normal glucose tolerance (NGT) ( n \u2009=\u200970), impaired glucose tolerance (IGT) ( n \u2009=\u200925) and DM ( n \u2009=\u200960). Results Galectin-3 levels were elevated in DM patients as compared to non-diabetic patients ( P \u2009=\u20090.02), while higher fibulin-1 levels were observed in HF patients with IGF and DM ( P \u2009=\u20090.07). Reduced LV contractile reserve was associated with increasing Gal-3 levels (\u3b2\u2009=\u2009\u22120.19, P \u2009=\u20090.03) although, this association was attenuated after adjustment for estimated glomerular filtration rate ( P \u2009=\u20090.66). Fibulin-1 was not associated with LV contractile reserve ( P \u2009=\u20090.71). Conclusions Galectin-3 and fibulin-1 levels were elevated in HF patients with impaired glucose metabolism. However, reduced LV contractile reserve among HF patients with DM does not to have an independent impact on plasma Gal-3 and fibulin-1 levels