体外抑菌试验评价核糖体表达筛选的抗菌肽活性

目的观察体外无细胞核糖体表达系统筛选得到的、能与细菌膜结合的多肽的体外抑菌活性变化,初步评价该筛选系统的可行性。方法采用核糖体展示系统和细胞膜模型筛选可结合于细胞膜的多肽,对筛选的多肽进行结构预测分析。选择形成α-螺旋结构可能性大、溶解性尚可的多肽(C13)进行合成。利用改良的微量肉汤稀释法测定C13和硫酸庆大霉素对G (金黄色葡萄球菌)和G-(大肠杆菌、伤寒杆菌)细菌的抗菌活性——最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。结果C13对试验细菌的MIC均为400mg/L,但在现有浓度范围对试验菌的MBC则未测得。结论体外无细胞核糖体表达系统筛选的抗菌肽C13具有一定的抑菌活性,表明利用人工膜模型和核糖体表达进行抗菌肽筛选的方法是可行的,但有效抗菌肽的筛选需进一步的抑菌试验证实。     

青霉源抗菌肽类霉肽素的体外抑菌活性研究

目的 研究抗菌肽类霉肽素(AF)的体外抑菌活性.方法 通过抑菌圈法和二倍稀释法检测AF的抗菌谱和对金黄色葡萄球菌的MIC;通过检测在AF中传代菌的敏感性确定细菌是否容易对AF产生抗药菌;将AF和细菌在不同温度和pH环境作用后检测抑菌活性,明确AF发挥活性的最适温度和pH值.结果 AF对大部分供试细菌和抗药菌有效,对金黄色葡萄球菌的MIC为0.8 mg/ml,金黄色葡萄球菌在AF中传代200代后敏感性不变.在14℃到30℃之间AF的抑菌活性随温度升高而降低,在pH 3到pH 10之间AF的活性随pH值升高而降低.结论 AF是一种对抗性菌有效的广谱抗菌肽,而且不容易诱导细菌产生抗药性.     

乳酸杆菌小分子抗菌肽产生菌的筛选及鉴定

乳酸链菌肽（Nisin）是由乳酸链球菌通过其核糖体合成产生的小分子抗菌肽，具有抑制细胞生长的作用，可用做食品天然防腐剂。其抑菌机制是小肽作用于细菌的细胞膜，在膜上形成离子通道，引起胞内物质的外漏使细菌失活。本文从酸菜汁中分离筛选出的乳酸杆菌HD1．7也能合成小分子抗菌肽，并且抑菌范围广。本研究扩大了小分子抗菌肽高产菌株的选育范围，有一定的实用意义。     

新型孔雀石绿衍生物的合成及其生物活性研究

目的以孔雀石绿(MG)为先导化合物,对其C环进行结构改造及修饰,系统评价合成的MG类似物的抗致病菌ESKAPE活性及细胞毒性。方法以芳香醛为原料,经过缩合、氧化反应得到13个MG类似物,其结构均经~1H-NMR、~(13)C-NMR和HRMS确证。采用肉汤微量稀释法测定目标化合物抗致病菌ESKAPE的最小抑菌浓度(MIC),用细胞增殖法(MTS)测试目标化合物的毒性。结果孔雀石绿及其C环改造类似物普遍对革兰阳性菌有抑制作用,而对革兰阴性菌无作用。其中3b对枯草芽孢杆菌的抗菌活性(MIC=0.39μmol/L)是MG(MIC=1.56μmol/L)的4倍;3f比MG的细胞毒性降低10倍以上。结论设计、合成了13种新型孔雀石绿衍生物,并对其进行生物活性评价,从中筛选出了抑菌活性高于孔雀石绿的化合物,为研制新型抗致病菌ESKAPE的药物提供了基础。     

42株形成生物被膜的嗜麦芽窄食单胞菌的药物敏感性研究

目的 研究单独及联合使用不同种类抗生素对嗜麦芽窄食单胞菌(Stenotrophomonasmahophilia,SML)体外生物被膜的抗菌活性. 方法 收集从患者分离的非重复SML 42株,分别采用微量接种针和硅胶膜片在水解酪蛋白肉汤中构建细菌生物被膜(bacterial biofilm)的体外模型,经过抗生素(左氧氟沙星、环丙沙星、头孢哌酮/舒巴坦、头孢他啶、哌拉西林、红霉素、磺胺甲噁唑、庆大霉素)作用20 h,超声振荡并测定孵育前后6 h吸光度(A)值的变化,计算相应的细菌生物被膜抑制浓度,进而测定红霉素与左氧氟沙星、头孢哌酮/舒巴坦、哌拉西林对细菌生物被膜的联合作用. 结果 SML对左氧氟沙星、磺胺甲噁唑和哌拉西林敏感率分别为83.33%、66.67%和54.76%,其他抗生素的耐药率均在50%以上.形成生物被膜后,细菌对抗生素的生物被膜抑制浓度大于相应的最小抑菌浓度(MIC)值. 结论 42株SML呈现多重耐药现象,形成生物被膜后耐药性增强.左氧氟沙星的抗菌活性在形成生物被膜前后均优于其他抗生素,联合红霉素与左氧氟沙星有助于增强杀菌效果.     

青霉源抗菌肽类霉肽素的体外抑菌活性研究

目的研究抗菌肽类霉肽素（AF）的体外抑菌活性。方法通过抑菌圈法和二倍稀释法检测AF的抗菌谱和对金黄色葡萄球菌的MIC;通过检测在AF中传代菌的敏感性确定细菌是否容易对AF产生抗药菌;将AF和细菌在不同温度和pH环境作用后检测抑菌活性,明确AF发挥活性的最适温度和pH值。结果AF对大部分供试细菌和抗药菌有效,对金黄色葡萄球菌的MIC为0．8mg／ml,金黄色葡萄球菌在AF中传代200代后敏感性不变。在14℃到30℃之间AF的抑菌活性随温度升高而降低,在pH3到pH10之间AF的活性随pH值升高而降低。结论AF是一种对抗性菌有效的广谱抗菌肽,而且不容易诱导细菌产生抗药性。     

阳离子卟啉衍生物的体外光动力抗菌活性研究

目的 研究阳离子卟啉衍生物介导的光动力抗菌化学疗法(CPD-PACT)对体外培养的绿脓杆菌的抑制作用,为研究其高效的抗菌作用特点提供依据.方法 采用二倍稀释法考察培养条件对CPD最小抑菌浓度(MIC)的影响,扩散法测定CPD的抑菌圈,活菌计数法测定CPD的体外抗菌后效应,并通过激光扫描共聚焦显微镜(CLSM)观察绿脓杆菌的活力和形态变化.结果 细菌接种量对MIC值存在一定的影响;培养基pH值的升高会使化合物的MIC值相应升高;血清蛋白体积分数的增加会使光反应的MIC值升高,而暗反应的MIC值降低.抑菌圈的大小主要取决于激光能量密度的强弱,而受光敏剂浓度的影响较小.CPD对绿脓杆菌有较强的抑制和杀灭作用,且存在明显的抗菌后效应,但光疗结束后存活的细菌会继续增殖.CLSM观察结果表明,CPD-PACT可破坏细菌外膜完整性,使细菌内容物泄露,活力减弱,最终导致细菌死亡.结论 CPD-PACT对绿脓杆菌具有高效的抗菌活性和明显的抗菌后效应,适合作为新一代抗菌候选药物进行深度开发.     

国产美洛培南的体外抗菌活性试验

目的:测定国产美洛培南(MEPM)和其它5种药物对136株临床分离菌的体外抗菌活性。方法:1)最小抑菌浓度(MIC)的测定:用琼脂二倍稀释法测定。     

抗解浸膏抗菌、抗病毒作用的观察

体外抗菌试验表明,抗解浸膏对金黄色葡萄球菌、表皮葡萄球菌、肺炎链球菌、甲及乙型溶血链球菌等革兰氏阳性细菌的MIC为1.56～56.0mg(生药)/ml,对大肠杆菌、克氏肺炎杆菌、变形杆菌、痢疾杆菌和嗜血流感杆菌的MIC_(50)为3.12～50.0mg(生药)/ml,对绿脓杆菌、产气杆菌的抑菌活性较低,MIG_(50)和MIC_(90)分别为50.0～200.0mg(生药)/ml,抗解浸膏还有一定的杀菌作用,MBC多数是MIC的2～4倍。抗解浸膏1:40的浓度对流感病毒A_3型在体外具有明显的抑制作用。     

左氟沙星抗结核作用的药效学研究

采用试管二倍稀释法测定试验药的最低抑菌浓度(MIC),以半数动物存活时间为指标比较药物的疗效。①左氟沙星在所试三种培养基中对人型结核菌(H_(37)RV)、牛型结核菌(Ravenel)和草分枝杆菌(M.phlei)的抑菌活性强于氧氟沙星(OFLX)(其MIC数值为OFLX的1/2);②左氟沙星在半流体培养基中对人型结核菌(H_(37)RV)和牛型结核菌(Ravenel)的杀菌活性强于氧氟沙星(其MBC数值为OFLX的1/2);③在本实验条件下,左氟沙星对小白鼠实验性结核病呈显著性或非常显著性疗效,显著优于同剂量OFLX的疗效,左氟沙星1mg/只的疗效近于OFLX的2mg/只的疗效。左氟沙星产品在体内体外均呈显著性抗结核活性,其体内外抗结核活性约为氧     

Dialysis culture for determination of MIC and MBC of benzylpenicillin against Borrelia burgdorferi

Minimal inhibitory concentration (MIC) of benzylpenicillin (Pen G) against strains of Borrelia burgdorferi has earlier been determined by a recently developed dialysis culture technique which provides a constant concentration of Pen G. To further investigate this method, both MIC and minimal bactericidal concentration (MBC) of Pen G against B. burgdorferi were determined and the results were compared with those obtained by other authors using different methods. The incubation period was 7 days and subcultures for MBC were observed for a further 2 weeks. The study showed results of MIC and MBC similar to those of broth microdilution, indicating sensitivity, but lower values than the majority of MIC and MBC results reported by other authors using broth macrodilution. It is essential for the results of antibiotic sensitivity testing in vitro against slowly growing bacteria like Borrelia burgdorferi that the concentration of antibiotics such as Pen G, which are unstable in solution, is constant during the incubation period.     

注射用清开灵冻干粉体外抗菌活性研究

目的：研究注射用清开灵冻干粉对临床分离致病菌的体外抗菌活性。方法：注射用清开灵冻干粉与市售清开灵注射液作比较，采用二倍稀释法，测定注射用清开灵冻干粉浓缩液对临床分离的47株致病菌的最低抑菌浓度（MIC）及最低杀菌浓度（憾），观察注射用清开灵冻干粉体外抗菌活性。结果：对金葡菌、大肠埃希菌、铜绿假单孢菌、肺炎克雷伯菌，注射用清开灵冻干粉与市售清开灵注射液均显示出良好的体外抗菌活性，注射用清开灵冻干粉体外抗菌活性强于市售清开灵注射液。按药液稀释度计算，注射用清开灵冻干粉浓缩液对金葡菌、大肠埃希菌、铜绿假单孢菌、肺炎克雷伯菌的MIC和MBC分别为市售清开灵注射液的1／4-1／2。结论：注射用清开灵冻干粉对临床分离的致病菌，具有较好的抗菌活性，且略优于市售清开灵注射液。     

Design and delivery of silver sulfadiazine from alginate microspheres-impregnated collagen scaffold

A reconstituted collagen scaffold impregnated with silver sulfadiazine (SSD) loaded alginate microspheres, capable of delivering the drug in a controlled manner has been developed. SSD-loaded alginate microspheres were prepared by modified water-in-oil emulsion technique through interfacial ionic gelation of alginate using CaCl2. The SSD-loaded microspheres were impregnated in pepsin-solubilized collagen, in situ, while inducing fibrillation and cast as thin scaffold. Morphological features of microspheres and microsphere-impregnated collagen were analyzed through SEM. Distribution homogeneity of impregnated microspheres, their in vitro behavior in (Dulbecco's modified minimal essential media) DMEM, and antibacterial efficiency against ATCC pathogens were determined. Initial drug load of 20% (w/w) with respect to alginate and 40% (v/v) of 2% alginate with respect to oil phase were found to produce microspheres of optimum drug entrapment (3%) and required size range (300-370 microm). In vitro drug release studies from the scaffold showed an initial burst release of 47.5% and a controlled release for 72 h with equilibrium concentration of 68.8%. SSD-loaded microspheres exhibited minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) levels of 32 and 40.2 microg/mL to both K. pneumoniae and E. coli respectively. P. aeruginosa showed MIC and MBC levels of 44.8 and 51.2 microg/mL respectively, while Staphylococcus aureus exhibited MIC and MBC at the same concentration range (57.6 microg/mL). The collagen-based scaffold impregnated with SSD-loaded alginate microspheres can deliver SSD in a controlled fashion, can control infection for extended time period with lesser dressing frequencies, and will enable easier assessment of wound.     

Highly efficient ribosome display selection by use of purified components for in vitro translation

Ribosome display is a powerful in vitro technology for the selection and directed evolution of proteins. The ribosome display process exploits cell-free translation to achieve coupling of phenotype and genotype by the production of stabilised ribosome complexes in which translated proteins and their encoding mRNA remain attached to the ribosome. Current ribosome display systems that are well proven, by the evolution of high affinity antibodies and the optimisation of defined protein characteristics, use an Escherichia coli cell extract for in vitro translation and display of an mRNA library. Recently, a cell-free translation system has been produced by combining recombinant E. coli protein factors with purified 70S ribosomes. We have applied this development in cell-free translation technology to ribosome display by using the reconstituted system to generate stabilised ribosome complexes for selection. We show that higher cDNA yields are recovered from ribosome display selections when using a reconstituted translation system and the degree of improvement seen is selection specific. These effects are likely to reflect higher mRNA and protein stability and potentially other advantages that may include protein specific improvements in expression. Reconstituted translation systems therefore enable a highly efficient, robust and accessible prokaryotic ribosome display technology.     

Antibacterial effects of Myristica fragrans, Zataria multiflora Boiss, Syzygium aromaticum, and Zingiber officinale Rosci essential oils, alone and in combination with nisin on Listeria monocytogenes

Plant essential oils and their components are perceived to exhibit antimicrobial activities. In this study the antibacterial effects of essential oil extracted from Myristica fragrans, Zataria multiflora Boiss, Syzygium aromaticum, and Zingiber officinale Rosci, alone and in combination with nisin, were evaluated against Listeria monocytogenes in brain heart infusion broth. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) with essential oils and pH values (5, 6, and 7), alone and in combination with nicin (5?μg?ml^?1), were determined. The individual essential oils all showed antibacterial effects against this bacterium. Combination of essential oils and nisin showed synergetic effects such that when the essential oils were utilized in combination with nisin, MIC and MBC decreased. By decreasing pH, these antibacterial effects were increased.     

Activities of selected medicinal plants against multi-drug resistant Gram-negative bacteria in Cameroon

Background

Medicinal plants are used worldwide for several human ailments including bacterial infections. The present work was designed to assess the in vitro antibacterial activities of some Cameroonian medicinal plants including Entada abyssinica, Entada africana, Pentaclethra macrophylla, Allexis cauliflora, Anthocleista leibrechtsiana, Carapa procera, Carica papaya and Persea americana against Gram-negative bacteria expressing multidrug resistant (MDR) phenotypes.

Methods

The microbroth dilution was used to determine the minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of the samples against eight bacterial strains belonging to four species, Escherichia coli, Enterobacter aerogenes, Klebsiella pneumoniae and Providencia stuartii.

Results

The extracts displayed selective antibacterial activities with the minimal inhibitory concentrations (MIC) values ranges of 64 to 1024 µg/mL. The most active extract was that from Pentaclethra macrophylla (TPM) that showed inhibitory activities against five of the eight (62.5%) tested bacteria. The lowest MIC value (64 µg/mL) was recorded with the crude extract of Entada africana against E. coli AG100A whilst the best MBC (256 µg/mL) value was also obtained with methanol extract of Persea americana against this bacterial strain.

Conclusion

The results of the present work provide baseline information on the possible use of Pentaclethra macrophylla, Entada africana and Entada abyssinica in the treatment of selected bacterial infections.     

Bactericidal activity of metronidazole against Bacteroides fragilis

Metronidazole was found to be active against Bacteroides fragilis strains isolated from human lesions. The minimal inhibitory concentrations (MIC) were from 0.16 to 2.5 mug/ml and the minimal bactericidal concentrations (MBC) were from 0.16 to 2.5 mug/ml; usually the MIC and MBC figures were equivalent. These levels are easily attainable in the serum following normal therapeutic doses. The drug is not toxic and side effects are rare and it would therefore seem highly suitable for treating Bacteroides infections and also may be considered prophylactically in certain situations that are described.     

Bacteriostatic and bactericidal activities of cyclines, macrolides and fluoroquinolones against Chlamydia trachomatis]

The in vitro activity of minocycline, doxycycline, erythromycin, roxithromycin, spiramycin, pefloxacin, and ofloxacin against ten C. trachomatis strains recovered from human genital tract specimens was evaluated. Mac Coy cell monolayers in 24-microwell plates were used. The C. trachomatis inoculum was 10(4) IFU/well. Appropriate dilutions of antibiotic were added and inclusions were detected by immunofluorescence using monoclonal antibodies. MICs were determined after 48 hours of exposure to each antimicrobial. The MIC90 for cyclines was 0.2 mg/l. Among tested macrolides, roxithromycin had a lower MIC than erythromycin (0.2 versus 0.4 mg/l) whereas spiramycin inhibited growth only in a concentration of 2 mg/l. Ofloxacin showed better activity than pefloxacin. Bactericidal activity was evaluated by determining two parameters: MBC1 (without transfer to new cells) measured the ability of a C. trachomatis particle to persist in a latent form within cells exposed to an antibiotic and to grow again following removal of the antibiotic, whereas MBC2 (with transfer to new cells) reflected infectivity of the bacteria after 48 hours exposure to the antimicrobial. None of the tested antibiotics was bactericidal according to both parameters. The ability of C. trachomatis to remain within antibiotic-exposed cells in a latent form was clearly demonstrated by the high MBC1 values. This feature may explain why recurrences are common in clinical practice.     

In vitro susceptibility of Listeria monocytogenes isolated from human blood and cerebrospinal fluid. A material from the years 1958-1985

The in vitro susceptibility of 156 strains of Listeria monocytogenes isolated since 1958 from human cerebrospinal fluid or blood to twelve antibiotics was determined by an agar dilution technique. Erythromycin (0.05), trimethoprim (0.2), netilmicin (0.2), and penicillin (0.2) were the most active drugs on weight basis (MIC90 0.05-0.2 micrograms/ml). Ampicillin and imipenem had MICs for 90% of the strains of 0.4 micrograms/ml. Ceftazidime was inactive (MIC90 greater than 100 micrograms/ml). Comparison of susceptibility pattern between strains isolated in different years showed that the antimicrobial susceptibility of L. monocytogenes has not changed during the last 25 years. The minimal bactericidal concentration (MBC) of penicillin was determined by a macro tube dilution method in ten recent isolates. Penicillin was bactericidal for all the strains with a MBC of 0.4-3.1 micrograms/ml, i.e. one to three two-fold dilutions above the MIC of 0.2-0.8 micrograms/ml, which means that no tolerant strains were found.