Identification of a new class of nitrogen fixation genes in Rhodobacter capsalatus: a putative membrane complex involved in electron transport to nitrogenase

DNA sequence analysis of a 12236 by fragment, which is located upstream of nifE in Rhodobacter capsulatus nif region A, revealed the presence of ten open reading frames. With the exception of fdxC and fdxN, which encode a plant-type and a bacterial-type ferredoxin, the deduced products of these coding regions exhibited no significant homology to known proteins. Analysis of defined insertion and deletion mutants demonstrated that six of these genes were required for nitrogen fixation. Therefore, we propose to call these genes rnfA, rnfB, rnfC, rnfD, rnfE and rnfF (for Rhodobacter nitrogen fixation). Secondary structure predictions suggested that the rnf genes encode four potential membrane proteins and two putative iron-sulphur proteins, which contain cysteine motifs (C-X₂-C-X₂-C-X₃-C-P) typical for [4Fe-4S] proteins. Comparison of the in vivo and in vitro nitrogenase activities of fdxN and rnf mutants suggested that the products encoded by these genes are involved in electron transport to nitrogenase. In addition, these mutants were shown to contain significantly reduced amounts of nitrogenase. The hypothesis that this new class of nitrogen fixation genes encodes components of an electron transfer system to nitrogenase was corroborated by analysing the effect of metronidazole. Both the fdxN and rnf mutants had higher growth yields in the presence of metronidazole than the wild type, suggesting that these mutants contained lower amounts of reduced ferredoxins.     

甲硝唑、欧维婷联合乳杆菌活菌胶囊治疗老年性阴道炎疗效观察

目的研究甲硝唑、欧维婷联合乳杆菌活菌胶囊治疗老年性阴道炎临床疗效。方法将45例老年性阴道炎患者分为对照组23例和治疗组22例,对照组采用甲硝唑治疗,治疗组采用甲硝唑、欧维婷联合乳杆菌活菌胶囊治疗,治疗1个疗程后,观察1个月。结果治疗组临床症状明显改善,与对照组比较,差异有统计学意义(P<0.05)。治疗组外阴阴道外观改善明显。结论甲硝唑、欧维婷联合乳杆菌活菌胶囊治疗老年性阴道炎能有效改善阴道健康状态,安全有效,建议临床推广使用。     

Synthesis,molecular docking and biological evaluation of metronidazole derivatives containing piperazine skeleton as potential antibacterial agents

Metronidazole has a broad-spectrum antibacterial activity. Hereby a series of novel metronidazole derivatives were designed and synthesized based on nitroimidazole scaffold in order to find some more potent antibacterial drugs. For these compounds which were reported for the first time, their antibacterial activities against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus were tested. These compounds showed good antibacterial activities against Gram-positive strains. Compound 4m represented the most potent antibacterial activity against S. aureus ATCC 25923 with MIC of 0.003 μg/mL and it showed the most potent activity against S. aureus TyrRS with IC₅₀ of 0.0024 μM. Molecular docking of 4m into S. aureus tyrosyl-tRNA synthetase active site were also performed to determine the probable binding mode.     

乳酸杆菌活菌制剂用于治疗老年性阴道炎合并细菌性阴道病临床探讨

目的探讨乳酸杆菌活菌制剂用于治疗老年性阴道炎合并细菌性阴道病的临床疗效。方法对118例老年性阴道炎合并细菌性阴道病患者随机分3组,分别予以乳酸杆菌活菌制剂局部用药和（或）口服甲硝唑,进行疗效比较。结果乳酸杆菌活菌制剂和甲硝唑联合应用对治疗老年性阴道炎合并细菌性阴道病疗效显著高于单一用药的疗效,组间差异具有显著性（P〈0.05）;复发率低于单一用药。结论乳酸杆菌活菌制剂与甲硝唑联合治疗老年性阴道炎合并细菌性阴道病有比较好的治疗效果,不易复发。     

布洛芬联合甲硝唑对慢性牙周炎龈沟液中细胞因子的影响

目的:研究布洛芬联合甲硝唑对慢性牙周炎的疗效和对龈沟液中细胞因子的影响。方法:选择2013年1月~2015年12月在我院进行诊治的慢性牙周炎患者82例,随机分为两组,观察组给予布洛芬联合甲硝唑治疗,对照组给予甲硝唑治疗,比较两组的临床疗效、龈沟液中细胞因子的变化和抗氧化作用。结果:观察组的有效率为82.93%(34/41),明显高于对照组的65.85%(27/41)(P0.05);两组治疗后的龈沟出血指数、牙菌斑指数、附着水平和牙周袋深度均明显降低(P0.05),且观察组降低的更为明显(P0.05);两组治疗后的超敏C反应蛋白、肿瘤坏死因子、白介素-6和白介素-8水平均明显降低(P0.05),且观察组降低的更为明显(P0.05);两组治疗后的超氧化物歧化酶和谷胱甘肽过氧化物酶水平均明显升高(P0.05),丙二醛和一氧化氮水平均明显降低(P0.05),且观察组更为明显(P0.05);两组不良反应发生率相比无明显差异(P0.05)。结论:布洛芬联合甲硝唑对慢性牙周炎疗效显著,可以有效降低炎症水平,减少自由基损伤,有助于牙周组织的重建及恢复。     

甲硝唑药膜联合盐酸米诺环素软膏治疗牙周病的临床疗效分析

目的:研究甲硝唑药膜联合盐酸米诺环素软膏治疗牙周病的临床疗效。方法:选择2014年1月~2016年1月在我院进行诊治的牙周病患者80例,随机分为两组。观察组采用甲硝唑药膜联合盐酸米诺环素软膏治疗治疗,对照组采用甲硝唑药膜治疗。观察并比较两组的疗效,牙周附着指数、牙菌斑指数、牙龈指数、牙齿松动度和白介素-6、白介素-8和肿瘤坏死因子的水平。结果:治疗4周后,观察组的治疗有效率为95.0%,明显高于对照组的90.0%(P0.05);治疗后两组的牙周附着指数、牙菌斑指数、牙龈指数和牙齿松动度均较治疗前明显降低(P0.05),且观察组的降低程度明显优于对照组(P0.05);治疗后两组的肿瘤坏死因子、白介素-6和白介素-8均较治疗前明显降低(P0.05),且观察组的降低程度明显优于对照组(P0.05);两组间丘疹、恶心、胃肠道反应和失眠的发生情况相比无明显差异(P0.05);观察组的复发率为2.5%,明显低于对照组的7.5%(P0.05)。结论:甲硝唑药膜联合盐酸米诺环素软膏能增强对牙周病各种致病菌的抑制作用,提高临床疗效,改善牙周状况和炎症状态,不良反应少,且复发率低,值得推广应用。     

Mechanism of metronidazole-resistance by isolates of nitroreductase-producing Enterococcus gallinarum and Enterococcus casseliflavus from the human intestinal tract

Enterococcus casseliflavus and Enterococcus gallinarum strains resistant to metronidazole, nitrofurantoin and nitrofurazone were isolated from fecal samples of a patient with recurrent ulcerative colitis treated with metronidazole. Unlike other metronidazole-resistant bacteria, these strains produced nitroreductase but metabolized metronidazole to compounds that could not be detected by liquid chromatography with UV or mass spectral analysis. Metronidazole-susceptible Clostridium perfringens grew equally well in spent cultures of Enterococcus spp. incubated with or without metronidazole. These data indicate that the nitroreductases produced by these Enterococcus strains did not activate metronidazole to bactericidal metabolites and these bacteria may reduce the effectiveness of metronidazole. We have indirect evidence for an alternative pathway that results in metronidazole resistance. These strains of enterococcus had nitroreductase so resistance should not have occurred.     

Reinvestigation of in vivo genotoxicity studies in man. I. No induction of DNA strand breaks in peripheral lymphocytes after metronidazole therapy

Although a rodent carcinogen, metronidazole is widely used in humans for the treatment of infections with anaerobic organisms. Metronidazole is mutagenic for microorganisms, but has a mainly negative data base for mammals and humans. Therefore, metronidazole is generally considered as a non-genotoxic carcinogen. Only the results of two human in vivo studies would allow the classification of metronidazole as genotoxic carcinogen: (1) the induction of DNA strand breaks; and (2) the induction of chromosome aberrations in peripheral lymphocytes after metronidazole therapy. Because the classification of metronidazole as genotoxic carcinogen would imply enormous consequences with respect to its application, both studies were reinvestigated very thoroughly. The present report describes the reinvestigation of the induction of DNA strand breaks after metronidazole therapy. Each two probes of lymphocytes of metronidazole-treated patients (3×500 to 3×750 mg/day for 5–8 days) were examined separately for the appearance of DNA strand breaks before and after treatment. In total, 400 nuclei were examined per patient. Immediately before the first, and 30 min to 2 h after the last application, 2×10 ml blood per patient was sampled, transported to the laboratory at 15–20°C to make DNA repair more difficult, and examined within the next 4–7 h for DNA strand breaks. At the same time, the individual metronidazole blood plasma levels were measured. In contrast to the published reports, no induction of DNA strand breaks after metronidazole therapy could be observed in the present study. As the applied doses (15 750 mg vs. 4800 mg) and the plasma level (up to 25 μg/ml vs. not measured) of metronidazole were much higher than in the published study, the relevance of the clearly negative result is obvious. As induction of DNA strand breaks is a frequent prerequisite for genotoxicity, metronidazole should be considered as a non-genotoxic carcinogen, and not as a genotoxic carcinogen.     

Micromatricial metronidazole benzoate film as a local mucoadhesive delivery system for treatment of periodontal diseases

The main objective of this study was to develop a local, oral mucoadhesive metronidazole benzoate (MET) delivery system that can be applied and removed by the patient for the treatment of periodontal diseases. Mucoadhesive micromatricial chitosan/poly(ε-caprolactone) (CH/PCL) films and chitosan films were prepared. thermal behavior, morphology, and particle size measurements were used to evaluate the prepared films. The effect of different molar masses of CH and different ratios of medium Mwt molar mass chitosan (MCH):PCL on water absorption, in vitro bioadhesion, mechanical properties, and in vitro drug release was examined. In vivo performance of the selected formulation was also evaluated. Differential scanning calorimetry examination revealed that MET existed mainly in amorphous form. Under microscopic examination, PCL microparticles were homogeneously dispersed in the films. The use of different molar masses of CH and different ratios of (MCH):PCL affected the size of the entrapped particles. Addition of PCL significantly decreased percentage water uptake and bioadhesion force compared with pure CH film. With regard to mechanical properties, the 2-layered film containing 1∶0.625 MCH:PCL had the best tensile properties. At fixed CH:PCL ratio (1∶1.25), the slowest drug release was obtained from films containing high molar mass CH. On the other hand, the 2-layered film that consisted of 1∶0.625 MCH:PCL had the slowest MET release. In vivo evaluation of the selected film revealed that metronidazole concentration in saliva over 6 hours ranged from 5 to 15 μg/mL, which was within and higher than the reported range of minimum inhibitory concentration for metronidazole. A significant in vitro/in vivo correlation under the adopted experimental conditions was obtained. Published: September 14, 2007     

Metronidazole resistance and virulence factors in Helicobacter pylori as markers for treatment failure in a paediatric population

The eradication rate obtained using the classical triple therapy containing metronidazole, amoxicillin and bismuth citrate, was determined in 57 paediatric patients with digestive disorders, according to the susceptibility to metronidazole of the Helicobacter pylori strains (determined by agar dilution) and the cagA and vacA status (determined by PCR). Eradication was obtained in 38 out of 43 patients (88.3%) infected by H. pylori with metronidazole MIC < or = 2 mg l(-1), in 3 out of 6 patients (50%) when MIC was 4-8 mg l(-1) and in 4 out of 8 patients (50%) when MIC was > 8 mg l(-1). Among patients infected with cagA+ and cagA- strains an eradication rate of 75% (6/8) and 75% (18/24) was found, and 50% (3/6) and 80% (21/26) among vacA s1- and vacA s2-infected subjects (P > 0.05). H. pylori eradication depends on the susceptibility of the strain to metronidazole, being higher in patients infected with susceptible H. pylori. However, according to our data the cagA or vacA status was not an important factor in treatment failure in the eradication of H. pylori.