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Objective:To investigate whether KtrA was a binding protein of c-di-AMP, the second messenger in Leptospira, and to explore the function and regulatory mechanism of the c-di-AMP-KtrA/B system. Methods:KtrA gene was amplified by PCR and cloned into pET42a plasmid to construct the pET42a ktrA prokaryotic expression vector. Then the vector was transferred into E. coli BL21DE3 to construct an engineering bacterium E. coli BL21DE3 pET42a-ktrA for the expression of recombinant KtrA (rKtrA). The expressed rKtrA was purified by affinity chromatography. BIAcore technology was used to detect the binding ability of rKtrA to c-di-AMP. Bacterial two-hybrid analysis was used to analyze the interaction between KtrA and KtrB in the leptospiral Ktr system with or without exogenetic c-di-AMP. The above genes were then complemented into the potassium transport-deficient E. coli mutants to analyze the function of the c-di-AMP-KtrA/B pathway. Results:An prokaryotic engineering bacterium for the expression of ktrA gene of Leptospira was constructed successfully. The purified rKtrA could specifically bind to c-di-AMP. There was interaction between KtrA and KtrB, but the interaction could be dissociated by c-di-AMP. The KtrA/B system was involved in potassium ion uptake and it was negatively regulated by c-di-AMP. Conclusions:Leptospiral KtrA was a c-di-AMP-binding protein and the c-di-AMP-KtrA/B system was involved in potassium ion transport.
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Objective:To investigate the effect of vancomycin (Vm)-loaded microbubbles (MBs) combined with ultrasound targeted microbubble destruction (UTMD) technique on the morphological structure, thickness and bacterial viability of methicillin-resistant Staphylococcus aureus (MRSA) biofilms.Methods:Vm-MBs were prepared by thin film hydration. Sterile coverslips in a diameter of 13 mm were placed in 24-well plates to construct in vitro biofilm models using MRSA as the test strain, and the biofilm morphology was observed by naked eye and light microscopy after crystal violet staining. LIVE/DEAD, SYTO59 and DIL were used to stain biofilms and MBs, respectively. After staining, the biofilm morphology and position of the biofilm in relation to MBs were observed using laser confocal scanning microscopy. The biofilms were divided into control group, Vm group, Vm-MBs group, UTMD group and Vm-MBs+UTMD group according to the random number table method, with 9 samples in each group. After biofilms of each group were treated accordingly for 24 hours, the morphological and structural changes of biofilms in each group were observed using laser confocal scanning microscopy and scanning electron microscopy following LIVE/DEAD staining; the difference in biofilm density in each group was measured with the aid of an enzyme marker following crystal violet staining; the difference in biofilm thickness and bacterial viability in each group were observed by laser confocal scanning microscopy. Results:The prepared Vm-MBs met the experimental requirements. The constructed biofilm model observed by naked eye, light microscopy and laser confocal scanning microscopy showed that the biofilm structure was dense with a relatively uniform thickness of (13.8±0.2)nm, a small amount of dead bacteria inside the membrane and the percentage of live bacteria of (94.9±0.3)%. Laser confocal scanning microscopy showed that MBs could penetrate into deeper layers of biofilms. After the respective treatment was given to each group for 24 hours, Laser confocal scanning microscopy and scanning electron microscopy following LIVE/DEAD staining showed that the biofilm morphological structure was most significantly disrupted in Vm-MBs+UTMD group compared to control, Vm, Vm-MBs and UTMD groups. In Vm-MBs+UTMD group, a large number of dead bacteria was observed, with only a few scattered planktonic bacteria and irregular changes in cell membrane morphology. Crystal violet staining showed that the biofilm density was significantly lower in Vm-MBs+UTMD group compared to control group ( P<0.05), while the differences between Vm, Vm-MBs and UTMD groups were not statistically significant (all P>0.05). Laser confocal microscopy showed that the biofilm thickness was thinner in Vm-MBs, UTMD and Vm-MBs+UTMD groups compared to control group (all P<0.05), with no significant difference between Vm group and control group ( P>0.05) and that the biofilm thickness was thinner in Vm-MBs+UTMD group compared to Vm, Vm-MBs and UTMD groups (all P<0.01), with no significant differences between the other groups (all P>0.05). Bacterial activity in Vm, Vm-MBs, UTMD and Vm-MBs+UTMD groups was significantly lower than that in control group (all P<0.01), with lower in Vm-MBs+UTMD group compared to Vm, Vm-MBs and UTMD groups (all P<0.01), but without significant difference between the other groups (all P>0.05). Conclusion:Vm-MBs combined with UTMD technology can effectively destroy the biofilm morphological structure to reduce biofilm thickness. Meanwhile, Vm-MBs combined with UTMD technology can release antibiotics and significantly decrease bacterial viability to improve antibiotic bactericidal efficacy.
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Objective To evaluate the efficacy of self-expanding metallic stents(SEMS)for acute proximal colon obstruction due to colon carcinoma.Methods From September 2004 to June 2010, a total of 81 patients(47 males and 34 females, aged 18-94 yr, mean 66.2 ± 7.5 yr)with acute proximal colon obstruction(proximal to spleen flex)caused by colon carcinoma were treated by SEMS.The success rate of stent drainage, safety of the procedure and the surgical removal rate of the carcinoma were evaluated.Results The tumors were located in transverse colon in 18(22.2%)patients, in hepatic flexure in 42 (51.9%)and in ascending colon in 21(25.9%).The success rate of stenting was 100%(81/81), and endoscopic decompression using SEMS placement was technically successful in 78 of 81 patients(96.3%).92.3%(72/78)patients underwent radical surgery 8 ± 1 days after stenting, among whom 5 underwent simultaneous hepatic metastasis foci resection and 3 others received partial resection of duodenum.Incidence of postoperative complications was 4.2%(3/72), including one case of poor healing and 2 cases of cardiopulmonary complications, which were all cured with conservative treatments.No perioperative death occurred.Conclusion Management of acute proximal colon obstruction due to colon carcinoma by using SEMS placement is effective and safe, which can be considered as a bridge method before curative surgery.