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101.
A new approach is described for the recovery of precious metals (PMs: Au, Pd and Ag) with >99% efficiency from aqueous solution utilising biogas produced during the aerobic growth of Klebsiella pneumoniae. Gold was recovered from electronic scrap leachate ( approximately 95%) by this method, with some selectivity against Cu. The recovered PM solids all contained metal and sulphur as determined by energy dispersive X-ray microanalysis (EDX). X-ray powder diffraction analysis (XRD) showed no crystalline metal sulphur compounds but a crystalline palladium amine was recorded. Silver was recovered as a sulphide (found by EDX), carbonate and oxide (found by XRD). EDX analysis of the Au-precipitate showed mainly gold and sulphur, with some metallic Au(0) detected by XRD. The gold compound was shock-sensitive; upon grinding it detonated to leave a sooty black deposit.  相似文献   
102.
Liu C  Skogman F  Cai Y  Lowary TL 《Carbohydrate research》2007,342(18):2818-2825
Described is the synthesis of the trisaccharide alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->3)-beta-D-GlcpNAcO(CH2)8N3, the glycan portion of which corresponds to the 'adaptor-primer' moiety linking the O-chain and core oligosaccharide in the lipopolysaccharide of several Escherichia coli and Klebsiella pneumoniae serotypes. This report represents the first synthesis of this trisaccharide motif, and in the route involved, a key step is a [2+1] coupling of a protected Manp-(1-->3)-alpha-D-Manp glycosyl donor with a GlcpNAc acceptor. The azido group was included in the target to facilitate future preparation of neoglycoconjugates.  相似文献   
103.
Short interfering RNA (siRNA) molecules with good gene-silencing properties are needed for drug development based on RNA interference (RNAi). An initial step in RNAi is the activation of the RNA-induced silencing complex RISC, which requires degradation of the sense strand of the siRNA duplex. Although various chemical modifications have been introduced to the antisense strand, modifications to the Argonaute2 (Ago2) cleavage site in the sense strand have, so far, not been described in detail. In this work, novel 2'-F-purine modifications were introduced to siRNAs, and their biological efficacies were tested in cells stably expressing human tartrate-resistant acid phosphatase (TRACP). A validated siRNA that contains both purine and pyrimidine nucleotides at the putative Ago2 cleavage site was chemically modified to contain all possible combinations of 2'-fluorinated 2'-deoxypurines and/or 2'-deoxypyrimidines in the antisense and/or sense strands. The capacity of 2'-F-modified siRNAs to knock down their target mRNA and protein was studied, together with monitoring siRNA toxicity. All 2'-F-modified siRNAs resulted in target knockdown at nanomolar concentrations, despite their high thermal stability. These experiments provide the first evidence that RISC activation not only allows 2'-F modifications at the sense-strand cleavage site, but also increase the biological efficacy of modified siRNAs in vitro.  相似文献   
104.
An important role has been recently reported for bacterial biofilm in the pathophysiology of chronic diseases, such as chronic rhinosinusitis (CRS). CRS, affecting sinonasal mucosa, is a persistent inflammatory condition with a high prevalence around the world. Although the exact pathological mechanism of this disease has not been elicited yet, biofilm formation is known to lead to a more significant symptom burden and major objective clinical indicators. The high prevalence of multidrug-resistant bacteria has severely restricted the application of antibiotics in recent years. Furthermore, systemic antibiotic therapy, on top of its insufficient concentration to eradicate bacteria in the sinonasal biofilm, often causes toxicity, antibiotic resistance, and an effect on the natural microbiota, in patients. Thus, coming up with alternative therapeutic options instead of systemic antibiotic therapy is emphasized in the treatment of bacterial biofilm in CRS patients. The use of topical antibiotic therapy and antibiotic eluting sinus stents that induce higher antibiotic concentration, and decrease side effects could be helpful. Besides, recent research recognized that various natural products, nitric oxide, and bacteriophage therapy, in addition to the hindered biofilm formation, could degrade the established bacterial biofilm. However, despite these improvements, new antibacterial agents and CRS biofilm interactions are complicated and need extensive research. Finally, most studies were performed in vitro, and more preclinical animal models and human studies are required to confirm the collected data. The present review is specifically discussing potential therapeutic strategies for the treatment of bacterial biofilm in CRS patients.  相似文献   
105.
The aim of this study was to investigate the frequency, molecular characterization, virulence genes, resistance genes and antimicrobial profile of nosocomial extended spectrum beta lactamase producing Klebsiella species. A total of 22 (12.2%) K. pneumoniae strains were isolated from 180 clinical samples collected from hospitalized patients in Egypt. K. pneumoniae biotypes were B1 (72.8%), B3 (13.6%) and B4 (13.6%). The isolates were classified for the capsular serotypes, 86.4% (20/22) were of K1 serotype, while only two isolates (13.64%) were of K2 serotype. Hypermucoviscous K. pneumoniae isolates accounted for 68.2%. Biofilm formation ability of K. pneumoniae was determined by microtitre plate method. The majority of the isolates (40.9%) were moderate biofilm producers, while 27.3% were strong biofilm producers. All K. pneumoniae strains were positive for fimH and traT genes, while magA was identified in only 63.6% of the isolates. The antibiotic susceptibility profile of the isolates (n = 22) was determined by the disc diffusion technique using 23 different antibiotics. Streptomycin and imipenem are the most effective antibiotics against 22 tested K. pneumoniae isolates with sensitivity rates of 63.64% and 54.54% respectively. All tested K. pneumoniae isolates showed high resistance to amoxicillin∕clavulanate (100%), cefuroxime (100%) and ceftazidime (95.45%). Extended spectrum beta lactamases (ESBL) production and the presence of ESBL-related genes were tested in the isolates. All the isolates tested positive for blaVIM, NDM1 and blaTEM, while only 81.8 %tested positive for the blaSHV gene. Increasing antimicrobial resistance in K. pneumoniae causing nosocomial infections limits the use of antimicrobial agents for treatment. Furthermore, the spread of biofilm, multiple drug resistant and ESBL-producing K. pneumoniae isolates is a public threat for hospitalized patients.  相似文献   
106.
107.
目的:观察硝黄散外敷联合加味五虎汤口服治疗痰热闭肺型肺炎支原体肺炎(MPP)患儿对肺功能和血清肿瘤坏死因子-α(TNF-α)、γ-干扰素(IFN-γ)、白介素-4(IL-4)水平的影响。方法:研究对象为我院2019年6月~2021年1月期间收治的MPP患儿80例,采用随机数字表法将患儿分为对照组(n=40,阿奇霉素抗感染治疗)和研究组(n=40,对照组基础上加用硝黄散外敷联合加味五虎汤口服治疗),均治疗7 d。比较两组患儿临床疗效,比较两组治疗前、治疗7 d后的中医证候积分、临床症状改善情况、肺功能和血清TNF-α、IFN-γ、IL-4水平。结果:研究组治疗7 d后的临床总有效率为92.50%(37/40),高于对照组的72.50%(29/40),差异有统计学意义(P<0.05)。与对照组相比,研究组的症状(咳嗽憋喘、发热、肺部干湿啰音)消失时间均更短(P<0.05)。与对照组相比,研究组治疗7 d后用力肺活量(FVC)、最高呼气峰流速(PEF)、第1秒最大呼气容积(FEV1)、FEV1/FVC均更高(P<0.05),研究组治疗7 d后的中医证候积分及血清TNF-α、IFN-γ和IL-4水平均更低(P<0.05)。结论:痰热闭肺型MPP患儿采用硝黄散外敷联合加味五虎汤口服治疗,可有效缩短患儿症状消失时间,显著改善其肺功能、血清炎症因子水平,疗效显著。  相似文献   
108.
Aims: The aim of this study is to assess the antibacterial activity of sodium citrate against Streptococcus pneumoniae and several oral bacteria. Methods and Results: The antibacterial activity was determined by broth microdilution method. The results showed that although Enterocuccus faecium OB7084 and Klebsiella pneumoniae OB7088 had high tolerance to sodium citrate, several oral bacteria including Fusobacterium nucleatum JCM8532T, Streptococcus mutans JCM5705T and Strep. pneumoniae NBRC102642T were susceptible. Furthermore, the bactericidal activity of sodium citrate against Strep. pneumoniae NBRC102642T was not influenced by pH in the range of 5·0–8·0, whereas that of sodium lactate was weakened at neutral or weak alkaline pH. When Strep. pneumoniae NBRC102642T was treated with sodium citrate for 2 h, many burst cells were observed. However, addition of MgCl2 or CaCl2 to an assay medium weakened the antimicrobial activity although ZnCl2 or MnCl2 did not influence. Conclusions: Independent of pH, sodium citrate inhibited the growth of oral bacteria, which suggests that the mechanism is different from that of sodium lactate. Significance and Impact of the Study: The results presented in this study would be available for understanding the antimicrobial property of sodium citrate.  相似文献   
109.
A Klebsiella oxytoca isolate which can produce significant levels of an exopolysaccharide using whey as a growth substrate has been reported. The plasmid profile of this isolate was shown to be different from that of the non-exopolysaccharide-producing K. oxytoca ATCC 43863. Irreversible curing of the single plasmid in the K. oxytoca isolate was achieved using 30 g acriflavin/ml. The ability to produce the exopolysaccharide was lost with the curing of the plasmid (parent strain produced a medium viscosity of 1260 cP at 1 s–1 compared to 1.6 cP at 200 s–1 produced by the cured strain). However, the ability to metabolize lactose was not significantly affected by curing, and both the parent and the cured strain produced similar levels of viable cells (~109 cfu/ml) after 62 h growth on lactose-rich medium. The exopolysaccharide-producing ability of the isolate was stable for at least 139 generations.  相似文献   
110.
A mutant ribitol dehydrogenase (RDH-F) was purified from Klebsiella aerogenes strain F which evolved from the wild-type strain A under selective pressure to improve growth on xylitol, a poor substrate used as sole carbon source. The ratio of activities on xylitol (500 mM) and ribitol (50 mM) was 0.154 for RDH-F compared to 0.033 for the wild-type (RDH-A) enzyme. The complete amino acid sequence of RDH-F showed the mutations. Q60 for E60 and V215 for L215 in the single polypeptide chain of 249 amino acid residues. Structural modeling based on homologies with two other microbial dehydrogenases suggests that E60 Q60 is a neutral mutation, since it lies in a region far from the catalytic site and should not cause structural perturbations. In contrast, L215 V215 lies in variable region II and would shift a loop that interacts with the NADH cofactor. Another improved ribitol dehydrogenase, RDH-D, contains an A196 P196 mutation that would disrupt a surface -helix in region II. Hence conformational changes in this region appear to be responsible for the improved xylitol specificity.  相似文献   
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