Due to the wide application of silver-containing dressings and silver-coated medical devices in clinical treatment; the extensive use of antibacterial agents and heavy metal agents in feed factories, Escherichia coli has formed the tolerance to silver ions. To systematically understand the known silver ion resistance mechanisms of E. coli, this article reviews the complex regulatory network and various physiological mechanisms of silver ion tolerance in E. coli, including the regulation of outer membrane porins, energy metabolism modulation, the role of efflux systems, motility regulation, and silver ion reduction. E. coli reduces the influx of silver ions by missing or mutating outer membrane porins such as OmpR, OmpC, and OmpF. It adapts to high concentrations of silver ions by altering the expression of ArcA/B and enhances the efflux capacity of silver ions under high-concentration silver stress via the endogenous Cus system and exogenous Sil system. Furthermore, the motility of bacteria is related to silver tolerance. E. coli has the ability to reduce silver ions, thereby alleviating the oxidative stress induced by silver ions. These findings provide a new perspective for understanding the formation and spread of bacterial tolerance and provide directions for the development of next-generation silver-based antimicrobials and therapies.
Escherichia coli/genetics* ; Silver/pharmacology* ; Drug Resistance, Bacterial ; Anti-Bacterial Agents/pharmacology* ; Porins/metabolism*

Objective To investigate the value of dynamic three-dimensional contrast-enhanced ultrasound (3D-CEUS) in evaluating therapeutic response of hepatoma treated with radiofrequency ablation (RFA).Methods Totally 48 cases of patients with hepatic carcinoma (48 lesions) admitted in Xiangya Hospital of Central South University from September 2012 to January 2014 were selected.All patients underwent radiofrequency ablation,of which 30 patients were diagnosed by pathology after surgery,18 patients by clinical diagnosis.All patients underwent two-dimensional contrast-enhanced ultrasound (2D-CEUS) and 3D-CEUS 1 month and 3 months after RFA treatment to evaluate the therapeutic response,and the results of contrast-enhanced ultrasound and enhanced computed tomography (CT) [or magnetic resonance imaging (MRI)] were compared.The final diagnostic results of pathologic biopsy or more than two imaging examinations [ultrasonography,CT,MRI,positron emission tomography (PET)],tumor markers,and more than 3 months follow-up of patients were used as the gold standard.The sensitivity,specificity and accuracy of dynamic 3D-CEUS,2D-CEUS,enhanced CT (or MRI) in the diagnosis of tumor inactivation were calculated respectively.Results After radiofrequency ablation,dynamic 3D-CEUS could provide more valuable information in 75.0％ (36/48) lesions,which contribute to assess the efficacy of radiofrequency ablation.While compared with 2D-CEUS,3D-CEUS did not change the diagnosis or clinical management in 12 (25.0％) lesions.40 of 48 lesions were found no-enhancement in entire CEUS procedure suggesting that the tumor completely inactivated,while 8 lesions showed local enhancement on the edge of lesion suggesting that part of the tumors were active.39 of 48 lesions showed no-enhancement and other 9 with irregular enhancement on enhanced CT (or MRI).The sensitivity,specificity and accuracy of CEUS and enhanced CT (or MRI) in detection of residual tumor after radiofrequency ablation were 80.0％,100％,95.8％ and 80.0％,97.4％,93.8％,respectively.Conclusions There was no statistical significance among 3D-CEUS,2D-CEUS and enhanced CT or MRI in evaluating therapeutic response of hepatoma treated with radiofrequency ablation.But 3D-CEUS can provide more valuable information,3D-CEUS has potential usefulness in the evaluation of percutaneous radiofrequency ablation of hepatic tumors.

Objective To evaluate the results of liver carcinoma treated by radiofrequency ablation(RFA) with color Doppler ultrasonography(CDU). Methods Hemodynamic changes of the interior and periphery of 212 nodules of liver carcinoma in 152 patients were investigated by CDU one week before and one month after RFA. Results Blood flow signals were found in 187 cancerous nodules before RFA, and were chiefly from mixed arterio-venous blood supply. After RFA, the blood flow signals of these 187 cancerous nodules completely disappeared in 133, were reduced in 40 and did not change in 14. Peripherar blood flow did not change in 51.2% of the tumors. Conclusions CDU is useful in evaluating the therapeutic effect of RFA in patients with liver carcinoma and may provide information for further treatment.