Gram-negative bacteria associated with timber as a potential respiratory hazard for woodworkers

The concentration and species composition of viableGram-negative bacteria was determined in samples of coniferous wood (Scots pine) and deciduous wood (European beech), and in air samples taken during the processing of these woods in sawmills. The concentration of Gram-negative bacteria in the sapwood of pine logs ranged from 1.0 × 10¹ to 6.2 × 10⁴ CFU/g. Their concentration in the air of the pine processing sawmill was within a range of 1.0 × 10²–6.3 × 10² CFU/m³. Concentration of Gram-negative bacteria in the sapwood of beech logs was similar to that in the sapwood of pine logs, ranging from 1.0 × 10¹ to 4.6 × 10⁴ CFU/g. However, the concentration of these bacteria in the air of a beech processing sawmill was within a range of 7.8 × 10³–1.3 × 10⁴ CFU/m³, being significantly higher than in a pine processing sawmill. Enterobacteriaceae strains, mostly Enterobacter spp. and Rahnella spp., made up 70–75% of Gram-negative bacteria isolated from pine and beech wood and from the air pollutedwith sawdust from these woods. The aerial exposure to Gram-negative bacteria possessing endotoxic andallergenic properties poses potential risk ofoccupational respiratory disorders among sawmillworkers, in particular those processing beech wood.     

Antibacterial activities of the methanol extracts of Canarium schweinfurthii and four other Cameroonian dietary plants against multi-drug resistant Gram-negative bacteria

Bacterial infections are among the major cause of morbidity and mortality worldwide. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of five Cameroonian edible plants namely Colocasia esculenta, Triumfetta pentandra, Hibiscus esculentus, Canarium schweinfurthii and Annona muricata against a panel of 19 multidrug resistant Gram-negative bacterial strains. The liquid broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the standard phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols, triterpenes and steroids, other classes of chemicals being selectively distributed. Canarium schweinfurthii extract showed the best activity with MIC values ranging from 64 to 1024 μg/mL against 89.5% of the 19 tested bacteria strains. MIC values below or equal to 1024 μg/mL were also recorded with Triumfetta pentandra, Annona muricata, Colocasia esculenta and Hibiscus esculentus extracts respectively against 15/19 (78.9%), 11/19 (57.9%), 10/19 (52.6%) and 10/19 (52.6%) tested bacteria. Extract from C. schweinfurthii displayed the lowest MIC value (64 μg/mL) against Escherichia coli AG100A_Tet. Finally, the results of this work provide baseline information for the use of C. esculenta, T. pentandra, H. esculentus, C. schweinfurthii and A. muricata in the treatment of bacterial infections including multidrug resistant phenotypes.     

Structure-activity relationship-based screening of antibiotics against Gram-negative Acinetobacter baumannii

To discover potent antibiotics against the Gram-negative bacteria, we performed a structure-activity relationship (SAR) study of YKsa-6, which was the most potent inhibitor of Staphylococcus aureus β-ketoacyl acyl carrier protein III in our previous study. We identified and selected 11 candidates, and finally screened two active compounds, YKab-4 (4-[(3-chloro-4-methylphenyl)aminoiminomethyl]benzene-1,3-diol) and YKab-6 (4-[[3-(trifluoromethyl)phenyl]aminoiminomethyl]phenol) as inhibitors of Acinetobacter baumannii KAS III (abKAS III). They showed potent antimicrobial activities at 2 or 8 μg/mL, specifically against Acinetobacter baumannii and a strong binding affinity for abKAS III. From the homology modeling, we defined the three-dimensional (3D) structure of abKAS III for the first time and found that it had an extra loop region compared with common Gram-negative bacteria derived KAS IIIs. The docking study revealed that the hydroxyl groups of inhibitors formed extensive hydrogen bonds and the complicated hydrophobic and cation-stacking interactions are important to binding with abKAS III. We confirmed that the hydrophobicity of these compounds might be the essential factor for their antimicrobial activities against Gram-negative bacteria as well as their structural rigidity, a cooperative feature for retaining the hydrophobic interactions between abKAS III and its inhibitors. This study may provide an insight developing strategies for potent antibiotics against A. baumannii.     

Triketones active against antibiotic-resistant bacteria: synthesis, structure-activity relationships, and mode of action

A series of acylated phloroglucinols and triketones was synthesized and tested for activity against methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Enterococcus faecalis (VRE) and multi-drug-resistant Mycobacterium tuberculosis (MDR-TB). A tetra-methylated triketone with a C₁₂ side chain was the most active compound (MIC of around 1.0 μg/ml against MRSA) and was shown to stimulate oxygen consumption by resting cell suspensions, suggesting that the primary target was the cytoplasmic membrane.     

Antibacterial activities of the methanol extracts of Albizia adianthifolia,Alchornea laxiflora,Laportea ovalifolia and three other Cameroonian plants against multi-drug resistant Gram-negative bacteria

In the last 10 years, resistance in Gram-negative bacteria has been increasing. The present study was designed to evaluate the in vitro antibacterial activities of the methanol extracts of six Cameroonian medicinal plants Albizia adianthifolia, Alchornea laxiflora, Boerhavia diffusa, Combretum hispidum, Laportea ovalifolia and Scoparia dulcis against a panel of 15 multidrug resistant Gram-negative bacterial strains. The broth microdilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the extracts. The preliminary phytochemical screening of the extracts was conducted according to the reference qualitative phytochemical methods. Results showed that all extracts contained compounds belonging to the classes of polyphenols and triterpenes, other classes of chemicals being selectively distributed. The best antibacterial activities were recorded with bark and root extracts of A. adianthifolia as well as with L. ovalifolia extract, with MIC values ranging from 64 to 1024 μg/mL on 93.3% of the fifteen tested bacteria. The lowest MIC value of 64 μg/mL was recorded with A. laxiflora bark extract against Enterobacter aerogenes EA289.Finally, the results of this study provide evidence of the antibacterial activity of the tested plants and suggest their possible use in the control of multidrug resistant phenotypes.     

Preparation of 8-hydroxyquinoline derivatives as potential antibiotics against Staphylococcus aureus

This work describes the preparation of quinoline compounds as possible anti-bacterial agents. The synthesized quinoline derivatives show anti-bacterial activity towards Staphylococcus aureus. It is interesting to observe that the synthetic 5,7-dibromo-2-methylquinolin-8-ol (4) shows a similar minimum inhibitory concentration of 6.25 μg/mL as compared to that of methicillin (3.125 μg/mL) against Staphylococcus aureus.     

The genetics of glycosylation in Gram-negative bacteria

In recent years there has been a dramatic increase in reports of glycosylation of proteins in various Gram-negative systems including Neisseria meningitidis, Neisseria gonorrhoeae, Campylobacter jejuni, Pseudomonas aeruginosa, Escherichia coli, Caulobacter crescentus, Aeromonas caviae and Helicobacter pylori. Although this growing list contains many important pathogens (reviewed by Benz and Schmidt [Mol. Microbiol. 45 (2002) 267-276]) and the glycosylations are found on proteins important in pathogenesis such as pili, adhesins and flagella the precise role(s) of the glycosylation of these proteins remains to be determined. Furthermore, the details of the glycosylation biosynthetic process have not been determined in any of these systems. The definition of the precise role of glycosylation and the mechanism of biosynthesis will be facilitated by a detailed understanding of the genes involved.     

一株类芽孢杆菌的分离鉴定及其抗革兰氏阴性菌活性测定

【背景】随着碳青霉烯类和多粘菌素类可转移耐药基因的发现及扩散,多重耐药革兰氏阴性细菌感染更加难以治疗。【目的】筛选有效拮抗革兰氏阴性菌的菌株,为新型抗生素的发掘奠定基础。【方法】利用胰蛋白胨大豆琼脂培养基筛选土壤源细菌,通过16S rRNA基因序列鉴定其种属;通过全基因组测序,antiSMASH比对分析菌株产抗生素潜能,双层琼脂平板法验证其抗菌活性;通过甲醇萃取其次级代谢产物,高效液相色谱串联质谱(HPLC-MS/MS)进行次级代谢产物分析。【结果】从北京周边土壤样品中分离到一株类芽孢杆菌CAU136 (Paenibacillus pabuli CAU136),经过生物信息学分析和antiSMASH比对,表明该菌株有较强合成次级代谢产物的潜能,双层琼脂平板法验证其能抑制多株革兰氏阴性菌生长,HPLC-MS/MS检测结果显示其可能分泌多粘菌素E。【结论】类芽孢杆菌CAU136可能分泌多粘菌素E,能有效拮抗革兰氏阴性菌。     

The utilization of morpholine as a sole nitrogen source by Gram-negative bacteria

The ability of Gram-negative bacteria to degrade morpholine when growing in pure culture is reported for the first time. Several bacterial strains were able to degrade morpholine and to utilize it as a sole nitrogen source but not as a sole carbon and energy source. The organisms studied were obtained from river water and activated sludge and could not be isolated directly on morpholine-containing media which always yielded growth of Gram-positive bacteria using morpholine as a carbon and energy source. The Gram-negative strains were isolated on the basis of their ability to grow on the structurally-related heterocyclc amines piperidine and pyrrolidine.     

部分革兰氏阴性菌脂多糖运输蛋白LptD的结构及功能研究进展

在革兰氏阴性菌中,脂多糖是外膜的重要组成部分,并参与构成细菌的固有免疫。而在大多数革兰氏阴性菌中,Lpt系统都是运输脂多糖的唯一途径,在该系统中LptD作为一个跨膜的外膜蛋白,也是脂多糖输出的最后一步,因此被许多学者称作脂多糖运输的"命门"。LptD参与多种重要的生物学功能,包括有机溶剂耐受性、疏水性抗生素耐受性、膜通透性等。但近来的研究表明,LptD最重要的功能是参与了脂多糖的运输,也因为其参与脂多糖运输而具有了多种功能。本文重点介绍部分革兰氏阴性菌LptD的蛋白结构及其功能研究进程,以期为进一步研究其它革兰氏阴性菌脂多糖运输通路(Lpt通路)及该通路上各蛋白间的相互作用机制提供参考。     

革兰氏阴性菌脂多糖运输系统的构成及作用机制

革兰氏阴性菌包含有两层组分不同的膜结构——内膜和外膜,对大多数革兰氏阴性菌而言,脂多糖(lipopolysaccharides,LPS)是其外膜上最主要的脂质成分,锚定在外膜小叶(the outer leaflet of the OM)上,是革兰氏阴性菌固有免疫的重要组成部分。脂多糖运输系统(lipopolysaccharide transport system,Lpt)将胞内装配完整的LPS正确装配到外膜,使得与脂多糖相关的阻渗、有机溶剂耐受性、疏水性抗生素耐受性、膜通透性等功能得以实现。该运输系统的正确作用主要依赖7个不同的脂多糖运输蛋白(Lpt ABCDEFG)协同完成,整个系统贯穿细菌内膜至外膜,由内膜上ABC转运体复合物Lpt B2FG、胞质内转运协同蛋白Lpt A/C及被许多学者称作脂多糖运输的"命门"的外膜蛋白复合物Lpt DE共同构成。本文就革兰氏阴性菌脂多糖的具体结构功能进行简介,进而综述脂多糖运输系统的7个蛋白的构成和作用机制,以期为进一步研究该系统中每个蛋白的功能提供理论基础及参考。     

Identification of a bactericidal component active against Gram-positive and Gram-negative bacteria in commercial ovomucoid and ovoinhibitor as lysozyme

During an investigation of the effect of protease inhibitors on the growth of Grampositive and -negative bacteria, commercial ovoinhibitor and ovomucoid were found to be strongly bactericidal. Both commercial inhibitors were fractionated by reversed phase chromatography and the bactericidal substance was identified as chicken egg white lysozyme. Lysozyme inhibited the growth of Gram-negative bacteria without addition of complement or EDTA. The use of ovoinhibitor and ovomucoid must be cautioned by the fact that the commercial preparations are contaminated with lysozyme.     

常见革兰阴性菌耐药性分析与合理用药研究

目的 分析芜湖市第一人民医院革兰阴性病原菌分布情况及对常见抗菌药物的耐药程度,为临床抗菌药物的选择及其合理使用提供参考。方法 收集2015年1月至2017年12月我院临床科室送检的细菌培养标本,采用法国生物梅里埃公司生产VITEK2 compact全自动微生物分析系统及其配套试剂盒进行细菌鉴定及药敏试验,数据采用WHONET 5.6软件进行统计分析。对年度耐药株数使用R语言3.4.0软件进行分析。结果 2015—2017年我院共检出病原菌3 728株,其中革兰阳性菌1 055株,占28.3%;革兰阴性菌2 673株,占71.7%。革兰阴性菌中主要致病菌为大肠埃希菌、肺炎克雷伯菌、铜绿假单胞杆菌、鲍曼不动杆菌,对青霉素类和第一代头孢菌素类抗菌药物高水平耐药。2017年这4种细菌对头孢唑林的耐药率均已达100.0%。鲍曼不动杆菌对头孢曲松的耐药率逐年上升,对头孢替坦连续3年耐药率均为100.0%,对氨苄西林/舒巴坦、氟喹诺酮类以及头孢吡肟耐药率未逐年上升,对亚胺培南耐药率变化显著,差异均有统计学意义（P<0.05）。铜绿假单胞杆菌对氨曲南耐药率逐年上升,对氨基糖苷类及头孢他啶耐药率逐年下降,差异均有统计学意义（P<0.05）。大肠埃希菌和肺炎克雷伯菌对头孢吡肟耐药率逐年下降,差异有统计学意义（P<0.05）。结论 我院住院患者病原菌以革兰阴性菌为主,不同病原菌对药物的敏感性各异,临床医生应结合患者情况和药敏结果综合分析,合理选用抗菌药物。     

Testing of different antibiotics against Gram-positive and Gram-negative bacteria isolated from plant tissue culture

Different Gram-positive and Gram-negative bacteria (Staphylococcus xylosus, S. aureus, S. cohnii, Bacillus sp., Corynebacterium sp., Pseudomonas vesicularis) were isolated from homogenized shoot tips of Drosera rotundifolia, Spatiphyllum sp., Syngonium cv. White butterfly, Nephrolepis exaltata cv. Teddy Junior. Growth inhibition of selected bacterial strains was examined using 28 different single antibiotics and 7 antibiotic mixtures. It was found that with the two mixtures Imipenem/Ampicillin and Imipenem/Penicillin G at concentrations of 5 mg l^–1 each, bacterial growth inhibition was most effective. Because of the lack of toxic effects on in vitro plants of 7 species it was proposed that these antibiotic mixtures can be applied advantageously to inhibit bacterial growth in tissue culture.     

Mannopeptimycins, a novel class of glycopeptide antibiotics active against gram-positive bacteria

Mannopeptimycins –, novel glycopeptides with activity against methicillin-resistant staphylococci and vancomycin-resistant enterococci, are purified from the fermentation broth of a strain of Streptomyces hygroscopicus, LL-AC98, and their structures characterized using spectroscopic analyses and chemical methods. The SAR data of the natural and synthetic esters demonstrate that the presence of hydrophobic groups near the terminal mannosyl moiety is critical for antibacterial potency. Scalable syntheses of 4,6-cyclic acetals and ketals on this moiety are used to produce significant quantities of the respective mannopeptimycin derivatives. These acetal and ketal derivatives exhibit potent activities against susceptible and resistant Gram-positive bacteria in both in vitro and in vivo experiments, comparable with or exceeding the activity of vancomycin. Studies on the mechanism of action suggest that the mannopeptimycins interfere with the late stages of bacterial cell wall biosynthesis. It is believed that these antibiotics inhibit the transglycosylation by binding to the transglycosylase substrate, lipid II.     

Enhancement of the antimicrobial activity and selectivity of GNU7 against Gram-negative bacteria by fusion with LPS-targeting peptide

Antimicrobial peptides (AMPs) provide a potential source of new antimicrobial therapeutics for the treatment of multidrug-resistant pathogens. To develop Gram-negative selective AMPs that can inhibit the effects of lipopolysaccharide (LPS)-induced sepsis, we added various rationally designed LPS-targeting peptides [amino acids 28–34 of lactoferrin (Lf28–34), amino acids 84–99 of bactericidal/permeability increasing protein (BPI84–99), and de novo peptide (Syn)] to the potent AMP, GNU7 (RLLRPLLQLLKQKLR). Compared to our original starting peptide GNU7, hybrid peptides had an 8- to 32-fold improvement in antimicrobial activity against Gram-negative bacteria, such as Escherichia coli and Salmonella typhimurium. Among them, Syn-GNU7 showed the strongest LPS-binding and -neutralizing activities, thus allowing it to selectively eliminate Gram-negative bacteria from within mixed cultures. Our results suggest that LPS-targeting peptides would be useful to increase the antimicrobial activity and selectivity of other AMPs against Gram-negative bacteria.     

革兰氏阴性菌血红素载体蛋白Hemophore的结构及作用机制

血红素作为宿主体内最丰富的铁离子来源,是致病菌营养竞争的主要目标,尤其对于血红素自身合成途径部分丧失的细菌。革兰氏阴性菌血红素转运系统由血红素载体蛋白(Hemophore)、外膜血红素受体、TonB-ExbB-ExbD复合物、ABC转运体等组成。Hemophore是存在于细菌细胞膜上或分泌到胞外环境中的一种蛋白。它能从宿主血红素结合蛋白中捕获血红素并将其传递给外膜受体。目前,在不同革兰氏阴性菌中已发现3种类型的Hemophore,分别是HasA、HxuA和HmuY型。本文将详细描述这3种Hemophore捕获血红素及与外膜受体相互作用的机制,以期为进一步研究其他细菌血红素载体蛋白的功能及作用机制奠定基础。     

Mechanism of chlorpromazine binding by Gram-positive and Gram-negative bacteria

Chlorpromazine forms charge-transfer complexes with xanthene dyes in bacteria. These complexes permit the differentiation of Gram-positive and Gram-negative bacteria in both light and polarization microscopy. The birefringence induced by the charge-transfer complex might explain the molecular basis of bacterial staining.The charge-transfer complexes formed between chorpromazine and xanthene dyes accumulate in the bacterial cell, mainly inside the bacterial cell wall. The complexes give the cells a color, which depends on the chemical composition of the staining structure, and in particular the polysaccharides of the cell wall in bacteria.Metachromatic granules were seen inside Gram-positive bacteria after chlorpromazine and rose bengal staining. Although the nature of these granules remains unclear, this type of binding may have a role in the inhibition of biochemical processes in the bacterial cells.     

Design,structural and functional characterization of a Temporin-1b analog active against Gram-negative bacteria

Background

Temporins are small antimicrobial peptides secreted by the Rana temporaria showing mainly activity against Gram-positive bacteria. However, different members of the temporin family, such as Temporin B, act in synergy also against Gram-negative bacteria. With the aim to develop a peptide with a wide spectrum of antimicrobial activity we designed and analyzed a series of Temporin B analogs.

Methods

Peptides were initially obtained by Ala scanning on Temporin B sequence; antimicrobial activity tests allowed to identify the TB_G6A sequence, which was further optimized by increasing the peptide positive charge (TB_KKG6A). Interactions of this active peptide with the LPS of E. coli were investigated by CD, fluorescence and NMR.

Results

TB_KKG6A is active against Gram-positive and Gram-negative bacteria at low concentrations. The peptide strongly interacts with the LPS of Gram-negative bacteria and folds upon interaction into a kinked helix.

Conclusion

Our results show that it is possible to widen the activity spectrum of an antimicrobial peptide by subtle changes of the primary structure. TB_KKG6A, having a simple composition, a broad spectrum of antimicrobial activity and a very low hemolytic activity, is a promising candidate for the design of novel antimicrobial peptides.

General significance

The activity of antimicrobial peptides is strongly related to the ability of the peptide to interact and break the bacterial membrane. Our studies on TB_KKG6A indicate that efficient interactions with LPS can be achieved when the peptide is not perfectly amphipathic, since this feature seems to help the toroidal pore formation process.     

重庆地区儿童2000年至2004年首位革兰阴性细菌和阳性细菌的耐药性监测

目的了解重庆地区儿童感染的分离至临床标本的首位革兰阴性细菌和阳性细菌对常用抗生素的耐药趋势,指导临床合理使用抗生素。方法常规方法分离、培养细菌,应用美国德灵公司WalkAway-40细菌鉴定仪对2000年至2004年我院细菌室分离至临床标本的首位革兰阴性细菌和阳性细菌共2854株进行细菌鉴定及药敏试验。结果2000年至2004年检出的首位革兰阴性细菌和阳性细菌分别为大肠埃希菌和金黄色葡萄球菌。2000年至2004年前5位革兰阴性菌5777株,革兰阳性菌1565株,其中大肠埃希菌2090株,金黄色葡萄球菌764株,分别占36.2%和48.8%;5年间大肠埃希菌对氨苄西林、头孢吡肟、头孢西丁、庆大霉素、亚胺培南、环丙沙星、头孢噻肟、头孢他啶的总耐药率分别为80.9%、37.5%、15.4%、54.0%、0.8%、34.0%、46.6%、46.2%;金黄色葡萄球菌对青霉素、红霉素、复方新诺明、万古霉素、阿莫西林/克拉维酸的总耐药率分别为95.6%、63.4%、5.8%、0%、11.0%。结论通过细菌耐药监测发现：大肠埃希菌对常用抗生素的总耐药率变化不大,金黄色葡萄球菌对常用抗生素的总耐药率有下降趋势,应引起临床医生重视。