银杏酸C17:1衍生物增效达托霉素抗粪肠球菌的发现与机制的初步研究

目的 发现有抗菌活性或是增效活性的银杏酸C17:1衍生物。方法 以银杏酸C17:1为底物，利用一些基团取代苯环上的羧基从而获得银杏酸C17:1衍生物，棋盘法设计试验，测定银杏酸C17:1及其衍生物联合抗生素的增效作用，通过测定Zeta电位、ROS、NPN吸收来探究增效机制。结果 银杏酸C17:1衍生物Ⅱ与达托霉素联合抗粪肠球菌的部分抑菌浓度指数(FICIs)为0.125~0.25，具有明显的协同效应，不仅能产生较高的活性氧，而且能在一定程度改变细胞膜的通透性。结论 银杏酸衍生物Ⅱ对达托霉素体外抗耐药株具有较好的增效作用，可能和ROS的激增以及膜通透性的改变有关。     

2017年安徽省某三甲医院细菌耐药性监测

目的 了解铜陵市人民医院2017年临床分离细菌对抗菌药物的耐药状况。方法 对2017年1-12月临床分离菌采用纸片扩散法(KB)进行药敏试验，按CLSI 2017年版标准判读药敏试验结果，采用WHONET 5.6软件进行数据分析。结果 临床分离细菌共3436株，其中革兰阳性菌719株，占20.9%；革兰阴性菌2717株，占79.1%。耐甲氧西林金黄色葡萄球菌(MRSA)和耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)的检出率分别为23.8%和72.3%，耐甲氧西林株对β-内酰胺类抗生素和其他测试抗菌药物的耐药率显著高于甲氧西林敏感株，未发现对万古霉素和替考拉宁耐药的葡萄球菌。粪肠球菌对青霉素、氨苄西林和呋喃妥因的耐药率较低，屎肠球菌对氯霉素的耐药率较低，5.3%屎肠球菌对万古霉素耐药。大肠埃希菌、克雷伯菌属(肺炎克雷伯菌和产酸克雷伯菌)和奇异变形菌中ESBLs的检出率分别为41.4%、50.7%和19.4%。肠杆菌科细菌中克雷伯菌属和沙雷菌属对碳青霉烯类抗生素耐药率较高，分别为37.5%和36.0%，其他菌属的耐药率低于3%。鲍曼不动杆菌对亚胺培南和美罗培南的耐药率分别80.3%和79.1%；铜绿假单胞菌对亚胺培南和美罗培南的耐药率分别为29.7%和28.4%。肺炎克雷伯菌、鲍曼不动杆菌和铜绿假单胞菌中广泛耐药株的检出率分别为31.3%(171/546)、0.6%(3/508)和0.7%(3/416)。结论 本院革兰阴性菌呈增多趋势，尤其广泛耐药的肺炎克雷伯菌应引起高度关注，做好细菌耐药性监测，加强临床抗菌药物的合理使用和医院感染控制。     

2014-2017年某医院152例尿路感染肠球菌耐药性监测分析

目的:了解2014年1月-2017年1月某医院尿液标本分离肠球菌的临床特点及耐药情况,为肠球菌经验治疗提供参考依据。方法:回顾性分析2014年1月-2017年1月分离自尿液标本肠球菌,VITEK2-compact微生物鉴定系统对细菌进行鉴定,纸片扩散法联合MIC法行抗生素敏感试验,WHONET 5.6和SPSS 20软件进行统计分析。结果:(1)2014年1月-2017年1月尿液标本共检出病原菌908株,主要是大肠埃希菌,其中屎肠球菌84株,粪肠球菌68株,是位于第2位和第3位的病原菌。(2)屎肠球菌对于氨苄西林、高水平庆大霉素、环丙沙星、左氧氟沙星、呋喃妥因的耐药率分别89.6%,63.2%,91.5%,85.7%,69.4%、明显高于粪肠球菌的24.2%(2=65.001,P=0.000)、40.4%(2=8.246,P=0.004)、56.6%(2=26.129,P=0.000)、51.2%(2=21.144,P=0.000)、12.2%(2=50.193,P=0.000);粪肠球菌对于氯霉素的耐药率为33.3%,显著高于屎肠球菌2.6%(2=27.035,P=0.000)。二者对于喹诺酮类抗生素都有较高的耐药率(51.2%)。(3)检出一株对万古霉素耐药的屎肠球菌,耐药率为1.2%(1/84);未检出对万古霉素耐药的粪肠球菌;未发现对利奈唑胺、替加环素耐药的肠球菌。(4)屎肠球菌多重耐药现象严重。结论:尿液标本屎肠球菌与粪肠球菌对抗菌药物耐药性差异大,屎肠球菌多重耐药现象形势严峻,已发现耐万古霉素的屎肠球菌,必须严密监控,尽早诊治,切断传播链。     

Enterococcus faecalis--a mechanism for its role in endodontic failure

AIM: The aim of this study was to identify a possible mechanism that would explain how E. faecalis could survive and grow within dentinal tubules and reinfect an obturated root canal. METHODOLOGY: Cells of Streptococcus gordonii DL1, Streptococcus mutans NG8, or E. faecalis JH2-2 were grown in brain heart infusion broth containing various amounts of human serum for 56 days. The ability of the three species to invade dentine and bind to immobilized type I collagen in the presence of human serum was assessed by dentine invasion and microtitre well experiments. RESULTS: All three species remained viable over the period of the experiment when grown in human serum. Cells of all three bacteria were able to invade dentine and bind to immobilized collagen. Both of these properties were inhibited by the presence of collagen in the cell solution. Human serum inhibited dentine invasion and collagen adhesion by S. gordonii DL1 and S. mutans NG8, whilst dentine invasion by E. faecalis JH2-2 was reduced in the presence of serum, but not inhibited, and binding to collagen was enhanced. CONCLUSIONS: It is postulated that a virulence factor of E. faecalis in failed endodontically treated teeth may be related to the ability of E. faecalis cells to maintain the capability to invade dentinal tubules and adhere to collagen in the presence of human serum.     

Starvation survival,growth and recovery of Enterococcus faecalis in human serum

The ability of Enterococcus faecalis to survive starvation for long periods in the obturated root canal is likely to be an important factor in the pathogenesis and maintenance of a persistent infection after endodontic treatment. The response of E. faecalis to starvation survival in water and glucose‐, phosphate‐ or amino acid‐limited chemically defined medium was studied, along with the capacity for growth and recovery of starved cells of E. faecalis in pooled human serum. After an initial rapid fall in cell numbers, a small remaining population of E. faecalis was able to survive in water for over 4 months and in nutrient‐limited media for extended periods. A high cell density at the onset of starvation was critical for the ability of E. faecalis to endure prolonged nutrient limitation. Upon starvation, a static population of starved cells developed and were apparently in a minimal metabolic state, since blocking cell wall synthesis with penicillin G or inhibiting DNA synthesis with norfloxacin during starvation resulted in limited change in the rate of loss of viable cells. In 50% serum, E. faecalis grew, then stabilized at a relatively constant population of 10⁶ colony‐forming units/ml for 4 months, irrespective of the initial cell density. In summary, E. faecalis is capable of withstanding prolonged periods of starvation in a minimal metabolic state provided that there is a high cell density at the onset of starvation. Starved cells were capable of recovery upon addition of human serum.     

Inactivation of local root canal medicaments by dentine: an in vitro study

AIMS: The aim of the study was to investigate the inactivation by dentine of the antibacterial activity of various commonly used local root canal medicaments. METHODOLOGY: The medicaments tested were saturated calcium hydroxide solution, 1% sodium hypochlorite, 0.5% and 0.05% chlorhexidine acetate, and 2/4% and 0.2/0.4% iodine potassium iodide. Dentine was sterilized by autoclaving and crushed into powder with a particle size of 0.2-20 microns. Aliquots of dentine suspension were incubated with the medicaments in sealed test tubes at 37 degrees C for 24 h or 1 h before adding the bacteria. In some experiments bacteria were added simultaneously with dentine powder and the medicament. Enterococcus faecalis A197A was used as a test organism. Samples for bacterial culturing were taken from the suspensions at 5 min, 1 h and 24 h after adding the bacteria. RESULTS: Dentine powder had an inhibitory effect on all medicaments tested. The effect was dependent on the concentration of the medicament as well as on the length of the time the medicament was preincubated with dentine powder before adding the bacteria. The effect of calcium hydroxide on E. faecalis was totally abolished by the presence of dentine powder. Similarly, 0.2/0.4% iodine potassium iodide lost its effect after preincubation for 1 h with dentine before adding the bacteria. The effect of 0.05% chlorhexidine and 1% sodium hypochlorite on E. faecalis was reduced but not totally eliminated by the presence of dentine. No inhibition could be measured when full strength solutions of chlorhexidine and iodine potassium iodide were used in killing E. faecalis. CONCLUSIONS: The dentine powder model appears to be an efficient tool for the study of interactions between local endodontic medicaments, dentine, and microbes.     

17%乙二胺四乙酸冲洗液对牙本质粪肠球菌黏附的影响

目的 研究17%乙二胺四乙酸（EDTA）冲洗液对促进牙本质粪肠球菌黏附的影响。方法 将48例半劈样本及12例牙本质片样本随机分为3个实验组和1个对照组,实验组分别经17%EDTA处理1、3、5 min,对照组经生理盐水处理5 min,接种粪肠球菌后通过扫描电子显微镜、激光共聚焦电子显微镜（CLSM）、菌落形成单位及组织学方法进行细菌黏附量的评价。结果 除组织学革兰染色显示,1 min组与对照组、3 min组的细菌侵入深度无明显差异（P>0.05）外,其余结果显示,实验组细菌生物膜厚度、侵入牙本质小管深度（CLSM测量）及菌落计数均大于对照组,差异具有统计学意义（P<0.05）;3个实验组之间比较,差异也具有统计学意义（P< 0.05）。结论 17%EDTA冲洗液可促进粪肠球菌对牙本质的黏附,且黏附量随处理时间的延长而增加。     

Short-term antibacterial activity of root canal sealers towards Enterococcus faecalis

AIM: To investigate the antimicrobial activity of root canal sealers on Enterococcus faecalis, either allowing or avoiding direct contact between sealers and bacteria. METHODOLOGY: Filter paper discs were immersed in standardized E. faecalis suspensions and exposed to freshly mixed sealers (MCS, AH Plus, Grossman's sealer, Sealapex, Apexit) in teflon wells for 30 min, with or without a filter membrane placed between filter paper discs and sealers (membrane-restricted contact test and direct contact test, respectively). After exposure, the filter paper discs were transferred to vials containing phosphate-buffered saline (PBS) and glass beads, and vigorously vortexed. PBS with resuspended bacterial cells was serially diluted and 25 microL droplets were seeded on TSA plates. The plates were incubated in air at 37 degrees C for 24 h and colony-forming units were counted. Using alpha = 0.05 as level for statistical significance, the data obtained were analysed using Student's t-test. RESULTS: In the direct contact test, MCS and AH Plus killed the bacteria to a level below the detection limit. They were followed in decreasing order of efficacy by Grossman's sealer, Sealapex and Apexit. In the membrane-restricted contact test, the sealers ranked: MCS, AH Plus, Grossman's sealer, Apexit and Sealapex, in descending order of antibacterial potency. MCS, AH Plus and Grossman's sealer significantly reduced the number of viable bacteria in both tests. Sealapex and Apexit were not statistically different from control. CONCLUSIONS: MCS, AH Plus and Grossman's sealer were effective in reducing the number of cultivable cells of E. faecalis. Calcium hydroxide-based sealers, Sealapex and Apexit were ineffective in this short-term experiment.