光滑念珠菌生物膜形成机制及其抗性研究

光滑念珠菌是亚洲第三或第四种最常见的侵袭性念珠菌病的病原体,占念珠菌血流感染的29%,其形成生物膜的能力被认为是最重要的毒力因子之一。光滑念珠菌生物膜的形成与医院感染的发病率和病死率高度相关。但是,对光滑念珠菌生物膜的研究少且分散。为此,本文将从环境因素、基因调控、抗性和抗性机制等多方面对光滑念珠菌生物膜进行综述。     

Thymol inhibits Candida albicans biofilm formation and mature biofilm

Candida albicans has a high propensity to develop biofilms that are resistant to traditional antifungal agents. Thymol is credited with a series of pharmacological properties including antimicrobial and antifungal effects. As C. albicans biofilms are known to be important factors underlying its virulence and pathogenicity, the aim of this study was to investigate whether thymol can interfere with biofilm formation as well as acting on mature biofilms. Tests of C. albicans strains ATCC 3153A and ATCC MYA 2876 showed that thymol interferes with the starting phases of biofilm production as well as with mature C. albicans biofilms. The metabolic activity of sessile cells was reduced by >90% at twice the minimum inhibitory concentration of planktonic cells. As biofilm is a multifactorial phenomenon, the multiple mechanisms of thymol (terpenes) could act on different steps in the evolution of mature biofilm.     

念珠菌生物被膜特性及抗生物被膜治疗

随着广谱抗生素的广泛使用,骨髓实体器官移植与医用材料植入治疗的增加,艾滋病、恶性肿瘤等免疫功能低下的患者增多,耐药念珠菌感染呈逐年上升趋势。耐药念珠菌感染通常与生物被膜的形成有关,生物被膜被认为是念珠菌重要的毒力因子,其形成与耐药性、侵袭力增强以及免疫逃避密切相关。本文从念珠菌生物被膜形成、耐药机制、免疫逃避及抗生物被膜治疗方面进行评述,以期为寻找新的药物靶点、为念珠菌感染的新型治疗策略提供新的思路。     

念珠菌生物被膜特性及抗生物被膜治疗

随着广谱抗生素的广泛使用,骨髓实体器官移植与医用材料植入治疗的增加,艾滋病、恶性肿瘤等免疫功能低下的患者增多,耐药念珠菌感染呈逐年上升趋势。耐药念珠菌感染通常与生物被膜的形成有关,生物被膜被认为是念珠菌重要的毒力因子,其形成与耐药性、侵袭力增强以及免疫逃避密切相关。本文从念珠菌生物被膜形成、耐药机制、免疫逃避及抗生物被膜治疗方面进行评述,以期为寻找新的药物靶点、为念珠菌感染的新型治疗策略提供新的思路。     

白念珠菌生物膜耐药性的研究进展

白念珠菌形成生物膜后耐药性明显增加,几乎对所有抗真菌药物(除了棘球白素和两性霉素B脂质体)具有高度耐药性.白念珠菌生物膜的耐药机制尚未完全清楚,可能与细胞外基质物理屏障作用、细胞营养受限生长代谢缓慢、耐药基因的表达、麦角甾醇的异常、耐药株的存在、附着面粗糙度、微环境的改变以及对抗机体的免疫防御等因素有关,它可能是一种多因素、多机制共同作用的结果.     

Fungal biofilm inhibition by a component naturally produced by Candida albicans yeasts growing as a biofilm

The purpose of this work was to demonstrate production by the Candida yeasts growing as a biofilm of a compound that reduces candidal biofilm growth. An in vitro model of Candida albicans biofilm associated with silicone catheters was used. Supernatant medium recovered from 24-h-old C. albicans (ATCC 3153) biofilm (S24h) was added during the course of new biofilm formation by four C. albicans strains (182, 444, 2091 or ATCC 3153). Addition of S24h to adherent C. albicans cells induced an inhibition of biofilm growth (P<0.001) but displayed no activity on established biofilms. Ultrafiltration and purification assays demonstrated that the antagonistic molecule is hydrophilic and <3000Da in size.     

鲍曼不动杆菌生物膜与耐药性的研究进展

鲍曼不动杆菌为革兰阴性杆菌,是导致医院感染的常见条件致病菌之一。由于其易产生耐药性及植入性医疗操作的增加,鲍曼不动杆菌生物膜导致的院内感染成为临床医师的极大挑战。因此,了解鲍曼不动杆菌的耐药机制具有重要的意义,分析其生物膜对耐药性的影响及其机制有助于开发新的联合治疗方案。此文从细菌生物膜的角度归纳鲍曼不动杆菌的耐药机制研究进展,讨论鲍曼不动杆菌生物膜的形成过程、调节因素以及对耐药性的影响,概述了亚致死剂量抗生素对鲍曼不动杆菌耐药形成的影响,为针对鲍曼不动杆菌生物膜所致感染制定适宜的治疗方案和防控耐药菌株传播提供参考。     

中药五倍子对白色念珠菌生物膜影响的体外研究

目的:比较五倍子水煎液、氢氧化钙和洗必泰三种根管消毒药物对白色念珠菌生物膜作用效果。方法:在96孔培养板底形成白色念珠菌生物膜,用XTT减低法定量分析生物膜形成过程及三种药物抑制生物膜内细胞生长80%的药物浓度。结果:48h细胞代谢水平最高,细胞活力及耐药性随培养时间延长而增强。结论:白色念珠菌生物膜对氢氧化钙耐药,对洗必泰敏感,五倍子对白色念珠菌生物膜初期阶段具有抑制作用。     

Reduction of Candida tropicalis biofilm by photoactivation of a Heterophyllaea pustulata extract

Context: Biofilm formation is an important problem, since this growth mode confers resistance to drugs usually used in therapeutics.

Objective: In vitro antifungal activity of extracts obtained from Heterophyllaea pustulata Hook f. (Rubiaceae) were studied against Candida tropicalis biofilms, evaluating the effect of irradiation and the oxidative and nitrosative stresses as possible mechanisms of action.

Materials and methods: Hexane, benzene, ethyl acetate and ethanol extracts were evaluated at three concentrations (0.2, 0.1 and 0.05?mg/mL) over mature biofilm, under darkness and irradiation. After 48?h of incubation, biofilm quantitation was performed by the O'Toole and Kolter method. Reactive oxygen species (ROS) was measured by nitro-blue tetrazolium (NBT) reaction and reactive nitrogen intermediates (RNI) by the Griess reagent. Superoxide dismutase activation (SOD, NBT assay) and total antioxidant system (FRAP test) were studied.

Results: Only the benzene extract at 0.2?mg/mL reduced the biofilms formation. The slight decrease achieved in darkness (17.06?±?2.80% reduction) was increased by light action (39.31?±?3.50% reduction), clearly observing a photostimulation. This great reduction was confirmed by confocal microscopy. In darkness, biofilm reduction was mediated by an increase in RNI, whereas under irradiation, the ROS action was most important. Although no SOD activation was observed, a strong stimulation of the total antioxidant system was detected. HPLC analysis established a high content of several anthraquinones in this extract.

Discussion and conclusion: Biofilm reduction by benzene extract was mainly mediated by oxidative stress triggered under light action, confirming a photodynamic sensitization, which could be attributed to its high content of photosensitizing anthraquinones.     

Antifungal resistance in non- albicans Candida species

Non- Candida albicans species have emerged as important bloodstream pathogens. They tend to have decreased susceptibility to antifungal agents in vitro and cause infections associated with high morbidity and mortality. Fluconazole resistance can emerge in any Candida spp., but is most commonly seen with Candida krusei, for which resistance is universal, and with Candida glabrata. Amphotericin B resistance has also been increasingly reported, most notably in isolates of Candida lusitaniae and Candida guilliermondii. Efforts are underway to correlate in-vitro antifungal susceptibility of individual Candida isolates with response to therapy of patients with candidemia. Future advances in this field might allow physicians to identify Candida isolates resistant to specific antifungal agents and thereby tailor therapy of candidemia.     

细菌药物主动外排系统在生物被膜耐药中的作用

摘要：细菌生物被膜的产生使传统抗菌药物难以对其进行有效的清除,进而导致严重感染的复发和持续性感染, 是人类目 前面临的又一新的挑战。生物被膜细菌中由于营养物质和代谢产物的积累,促使药物主动外排系统相关基因表达明显增加, 使 外排泵转运多种不同类型的化合物能力增强,从而产生多重耐药表型,是引起细菌耐药的主要机制之一;外排泵基因的表达对 生物被膜细菌的生长和耐药性增强方面有着重要作用。本文从生物被膜耐药的影响因素、药物主动外排系统参与生物被膜形成 及其影响、外排泵抑制剂对生物被膜耐药的影响几个方面对细菌药物主动外排系统在生物被膜耐药中的作用进行综述。     

细菌生物膜形成和耐药机制研究进展

细菌生物膜是一个具有结构性、协词性和功能性的高度组织群体，其相关感染因为对抗生素耐药性极强成为临床难治性感染的重要原因之一。本文参阅近年来国内外研究结果，介绍了细菌生物膜的结构及特性，重点讨论其形成发展，抗生素耐药机制及防治策略方面的研究进展，对于寻找有效控制手段，指导临床合理用药和开发新药有重要意义。     

假丝酵母菌属的耐药性分析

目的 了解我院深部真菌感染的种类和耐药特点,为合理使用抗真菌药物提供病原学依据.方法 对2009-2010年分离的假丝酵母菌属进行菌种分布和耐药性分析.结果 495株假丝酵母菌属占总分离病原菌(3027株)的比例为16.4％,其中白色假丝酵母菌397株,占80.2％;从呼吸道标本中分离出443株,占89.5％;白色假丝酵母菌对两性霉素B、5-氟胞嘧啶、氟康唑、伏立康唑、伊曲康唑的耐药率分别为0.3％ (1/397)、1.5％(6/397)、2.8％ (11/397)、4.8％( 19/397)、10.6％(42/397).结论 白色假丝酵母菌是真菌感染的主要病原菌,早期诊断和合理使用抗真菌药物是防治真菌感染的关键.     

白色念珠菌耐药性产生的分子机制

耐氟康唑的白色念珠菌已成为临床长期用药治疗的一个突出性问题,目前认为白色念珠菌耐药性产生的分子机制,主要包括麦角甾醇生物合成通路中关键靶酶的变异和高表达、多药耐药蛋白对真菌胞内药物浓度的影响以及生物被膜的形成等.     

热带念珠菌外排泵耐药的研究

目的研究耐氟康唑热带念珠菌临床株Fc30的外排泵耐药机制。方法运用半定量RT-PCR技术研究外排泵基因mdr1 mRNA水平与耐药的相关性。结果耐药株Fc30的mdr1基因mRNA灰度比值约为敏感株Fc17的2．3倍。结论与敏感株相比，耐氟康唑热带念珠菌Fc30外排泵基因mdr1过度表达与耐药相关。     

Immunosuppression and recovery of drug-impaired host resistance against Candida albicans infection by oxoglaucine.

The immunosuppressive action of aporphinoid alkaloid oxoglaucine was studied in experimental Candida albicans (C. albicans) infection in mice. The alkaloid augmented host resistance to pathogen applied to mice (6-8 weeks of age) at a low dose of 2 mg kg(-1) in 3 days and impaired it at a high dose of 10 mg kg(-1). The suppressive activity observed under the latter schedule correlated with the inhibited proliferative response of splenic cells to mitogens and with decreased popliteal lymph node (PLN) reaction to C. albicans. Treatment of mice with oxoglaucine (at the age of 5 days) at a dose of 5 mg kg(-1) in 3 consecutive days increased the susceptibility to Candida inoculation at the age of 6 weeks. Delayed type hypersensitivity (DTH) response to C. albicans was enhanced after pretreatment of adult mice and was suppressed after administration to newborn mice. Long-time treatment (10 days) with oxoglaucine, cyclophoshamide or prednisolone at a dose of 10 mg kg(-1) increased the rate of mortality of Candida-infected mice. Combined pretreatment of mice with cyclophosphamide or prednisolone (5 days at a dose of 5 mg kg(-1)) followed by oxoglaucine (5 days at a dose of 5 mg kg(-1)), prolonged the survival of infected mice.     

Enhancement by ubenimex (bestatin) of host resistance to Candida albicans infection.

Ubenimex is a low molecular weight microbial metabolite which has been demonstrated to have antitumor and immunomodulatory activities. In this study, the protective effect of ubenimex on Candida albicans infection was investigated in normal and immunosuppressed mice. In normal mice, treatment with ubenimex at 0.5, 5 and 25 mg/kg for 5 days prior to infection prolonged survival time in a dose-dependent manner. In immunosuppressed mice treated with a single dose of cyclophosphamide 4 days prior to infection, ubenimex treatment at 5 mg/kg for 5 days significantly increased the number of survivors. Ubenimex-treated mice had a significant increase in number of peritoneal exudate cells with neutrophils as well as enhanced functions, including phagocytosis and active oxygen production. These results suggest the potential usefulness of ubenimex as a prophylactic agent for the management of patients with opportunistic fungal infections.