白念珠菌生物膜及其研究进展

白念珠菌生物对多种传统抗真菌药物高度耐药,日益增多的白念珠菌生物膜相关感染引起抗真菌药物治疗的失败加重了患者及社会的经济负担,这已经成为临床医生所面临的重要问题.该文旨在阐明白念珠菌生物膜的临床重要性,并从多方面阐述白念珠菌生物膜的结构特点、形成机制、防治现状的最新研究进展,为白念珠菌的研究及临床防治策略提供参考.     

白念珠菌耐药的分子机制研究进展

近年来,免疫受损人群不断增多,该人群念珠菌病发病率呈上升趋势。随着抗真菌药物的广泛应用,临床分离到的白念珠菌耐药株增多,有关白念珠菌对抗真菌药物的耐药机制的研究又有了进一步的进展。就白念珠菌对唑类、多烯类、5-氟胞嘧啶、棘白菌素类等抗真菌药物的耐药机制方面的研究进展,作了介绍。     

白念珠菌耐药机制新进展

近年来对于深部真菌感染的研究报道越来越多,其已日益成为一些重要疾病临床治疗过程中的常见并发症,其中,白念珠菌病的发病率仍居高不下.虽然目前有多种抗真菌药物应用于临床,但其耐药现象愈来愈严重,给临床治疗带来了极大的挑战.近来有关白念珠菌耐药机制的研究有了较新的进展.该文就新发现的白念珠菌的耐药机制,作一概述.     

抗白念珠菌感染的疫苗及抗体研究进展

白念珠菌是与人类共生的条件致病真菌,能引起免疫力低下患者皮肤黏膜和全身系统性持续感染.系统性念珠菌病是引起免疫力低下患者死亡的主要原因之一.由于临床缺乏念珠菌病的早期诊疗手段、可用的抗真菌药物种类有限且毒副作用大、耐药菌株越来越普遍、新药研发难度大等因素,抗真菌治疗依然面临着严峻挑战.目前有较多研究者致力于阐明白念珠菌感染的宿主免疫应答机制,并试图研发抗白念珠菌感染的免疫治疗方法,使免疫治疗有望成为预防和治疗真菌感染的有效手段.该文将几种抗白念珠菌感染的疫苗和抗体研究进展作简要概述,旨在为新型抗白念珠菌感染疫苗及抗体的研究提供参考.     

白念珠菌耐药机制研究进展CSCD

白念珠菌是侵袭性念珠菌病最常见的致病菌,其耐药问题使临床治疗面临着严峻的挑战。白念珠菌常见的耐药机制包括药物靶点突变或上调、药物外排增加、生物被膜形成等,近年来代谢调节、线粒体功能改变、选择性剪切等机制也受到了广泛关注。了解白念珠菌耐药机制有助于探索研究全新结构的抗真菌药物和开发更多有效的抗耐药真菌策略。该文就白念珠菌耐药机制研究进展进行综述。     

光滑念珠菌的生物学、流行病学以及耐药机制研究进展

随着HIV感染患者的增多、器官移植、放疗化疗及抗真菌药物的广泛使用,近年来全世界范围内念珠菌感染趋势发生了明显变化,除白念珠菌外,光滑念珠菌在临床上的检出率逐年增加,在部分国家和地区已成为第二常见的侵袭性念珠菌。光滑念珠菌临床分离株通常对一线抗真菌药物高度耐药,由于目前治疗策略匮乏,其造成的系统感染死亡率可高达50%。为了进一步加深人们对光滑念珠菌的认识,研发遏制其感染的诊疗策略,本文综述了近年来光滑念珠菌的流行病学、毒力因子以及耐药机制等方面的进展,为国内同行深入探究其耐药特性和致病机理提供参考。     

营养感应与白念珠菌致病机制研究进展

营养元素是白念珠菌定植和致病的关键因素之一,作为人体真菌微生物组的一部分,白念珠菌能够特异性感应宿主微环境中营养物质的变化,及时做出适应性反应,为其生长、繁殖和侵袭宿主提供营养支持;同时白念珠菌还能反馈作用于人体,在机体免疫力低下或肠道菌群失调时由共生菌转化为致病菌引发严重的念珠菌病。目前关于营养感应与白念珠菌致病的分子机制已经有很多研究。本文概述了近年来营养感应与白念珠菌致病机制的相关研究结果,总结了碳源、氮源、磷营养以及多种金属元素在白念珠菌致病过程中发挥的作用,旨在为系统认识白念珠菌致病机制以及开发新型抗真菌药物提供新的研究思路。     

白念珠菌黏附基因研究进展

白念珠菌具有很强的黏附和侵袭能力,其黏附特性是致病力的重要原因,与白念珠菌黏附相关的基因称为黏附基因。对黏附基因的研究不仅有助于更好地解读白念珠菌的致病机制,而且也为研制新的抗真菌药物和真菌疫苗提供了理论依据。     

中草药抗白念珠菌作用研究进展

白念珠菌,是人类最常见的真菌病原体,可引起各种浅表及深部真菌病,对常用抗真菌药物易产生耐药.文章就近年来有关中草药抗白念珠菌的相关临床及实验研究进行综述,主要从中草药抗白念珠菌的作用机制及其活性成分、单味及复方中草药制剂抗白念珠菌作用、中西药协同抗白念珠菌作用几个方面进行阐述.     

白念珠菌液泡的致病性作用

白念珠菌是常驻人体的条件致病性真菌,与机体处于共生状态,在正常人体不致病。当某些因素破坏这种平衡状态,如当机体免疫力下降和黏膜屏障功能受损时,白念珠菌由酵母相转为菌丝相,在局部大量生长繁殖,侵袭力增加,引起皮肤、黏膜甚至全身性的念珠菌病。随着真菌对经典药物耐药性的出现,新型抗真菌药物的研发就显得尤为重要。目前以白念珠菌液泡作为抗真菌药物靶点的研究正深入开展。该文就白念珠菌液泡功能在白念珠菌致病性中的研究进展作一综述。     

Direct comparison of the pharmacodynamics of four antifungal drugs in a mouse model of disseminated candidiasis using microbiological assays of serum drug concentrations

The aim of this study was to compare the pharmacodynamics of the azole antifungal drugs fluconazole, itraconazole and ketoconazole, and the polyene antifungal amphotericin B, in a mouse model of disseminated Candida albicans infection. In order to directly compare effective serum concentrations of these antifungals, drug concentrations were assayed microbiologically by measuring inhibition of C. albicans mycelial growth (mMIC) in a mouse serum-based assay (serum antifungal titer). Efficacy in the mouse infection model was determined using an organ-based (kidney burden) endpoint. For all four drugs, the serum antifungal titers, 8 hr after administration of single doses of drugs at a range of drug concentrations, correlated closely with C. albicans kidney fungal burden in the mouse model. The results showed that determining serum antifungal titer may be used to accurately represent kidney fungal burden in a mouse model of disseminated candidiasis and allowed direct comparison of the pharmacodynamics of differing classes of antifungal drugs.     

Coprisin-induced antifungal effects in Candida albicans correlate with apoptotic mechanisms

Coprisin is a 43-mer defensin-like peptide from the dung beetle, Copris tripartitus. Here, we investigated the induction of apoptosis by coprisin in Candida albicans cells. Coprisin exerted antifungal and fungicidal activity without any hemolytic effect. Confocal microscopy indicated that coprisin accumulated in the nucleus of cells. The membrane studies, 1,6-diphenyl-1,3,5-hexatriene, calcein-leakage, and giant unilamellar vesicle assays, confirmed that coprisin did not disrupt the fungal plasma membrane at all. Moreover, the activity of coprisin was energy- and salt-dependent. Next, we investigated whether coprisin induced apoptosis in C. albicans. Annexin V-FITC staining and TUNEL assay showed that coprisin was involved with both the early and the late stages of apoptosis. Coprisin also increased the intracellular reactive oxygen species level, and hydroxyl radicals were included at high levels among the species. The effect of thiourea as a hydroxyl radical scavenger further confirmed the existence of the hydroxyl radicals. Furthermore, coprisin induced mitochondrial membrane potential dysfunction, cytochrome c release, and activation of metacaspases. In summary, this study suggests that coprisin could be a model molecule for a large family of novel antimicrobial peptides possessing apoptotic activity.     

Silver nanoparticles induce apoptotic cell death in Candida albicans through the increase of hydroxyl radicals

Silver nanoparticles have been shown to be detrimental to fungal cells although the mechanism(s) of action have not been clearly established. In this study, we used Candida albicans cells to show that silver nanoparticles exert their antifungal effect through apoptosis. Many studies have shown that the accumulation of reactive oxygen species induces and regulates the induction of apoptosis. Furthermore, hydroxyl radicals are considered an important component of cell death. Therefore, we assumed that hydroxyl radicals were related to apoptosis and the effect of thiourea as a hydroxyl radical scavenger was investigated. We measured the production of reactive oxygen species and investigated whether silver nanoparticles induced the accumulation of hydroxyl radicals. A reduction in the mitochondrial membrane potential shown by flow cytometry analysis and the release of cytochrome c from mitochondria were also verified. In addition, the apoptotic effects of silver nanoparticles were detected by fluorescence microscopy using other confirmed diagnostic markers of yeast apoptosis including phosphatidylserine externalization, DNA and nuclear fragmentation, and the activation of metacaspases. Cells exposed to silver nanoparticles showed increased reactive oxygen species and hydroxyl radical production. All other phenomena of mitochondrial dysfunction and apoptotic features also appeared. The results indicate that silver nanoparticles possess antifungal effects with apoptotic features and we suggest that the hydroxyl radicals generated by silver nanoparticles have a significant role in mitochondrial dysfunctional apoptosis.     

Quercetin-induced yeast apoptosis through mitochondrial dysfunction under the accumulation of magnesium in Candida albicans

Latterly, the upsurge in use of antifungal drugs has brought about the emergence of several drug-resistance strains, making it skeptical to continue relying on current therapeutic regime. In the necessity of resistance-free antifungal agent, flavonoids presented possibilities of replacing existing drugs, displaying antifungal activity against pathogenic fungi. Among them, quercetin, one of the most representative flavonoids, exhibited antifungal activity against Candida albicans. To inspect the further understanding regarding quercetin, the antifungal mode of action of quercetin was investigated. In the initial step, the apoptosis was monitored after quercetin treatment. Moreover, intracellular levels of Mg²⁺ was assessed and was determined that Mg²⁺ increase occurred under the influence of quercetin. In addition, several features of mitochondrial dysfunction were monitored. Mitochondrial dysfunction triggers decrease in mitochondrial redox levels and leads to disruption in mitochondrial antioxidant system. Increased intracellular ROS and decreased intracellular redox levels were also displayed, indicating the occurrence of overall disruption in antioxidant systems. Sequentially, DNA fragmentation was observed and this DNA damage in turn induces apoptosis. In analyses, hexaamminecobalt(III) chloride (Cohex) was applied to inhibit Mg²⁺ transport between cytosol and mitochondria. Cohex attenuated the effects induced by quercetin, which demonstrates that the presence of Mg²⁺ is essential in quercetin-induced apoptosis.     

美浮特皮肤抗菌液对致足癣真菌抗真菌后效应的体外研究

目的：评价美浮特^R皮肤抗菌液对致足癣真菌皮肤癣菌和白念珠菌的体外抗真菌活性及抗真菌后效应。方法采用美国 CLSI M27-A3和 M38-A2方案测定美浮特皮肤抗菌液对足癣常见致病真菌的最低抑菌浓度（ MIC）;并以白念珠菌（ATCC90028）为指示菌测定美浮特皮肤抗菌液测定时间-杀菌曲线,同时测定其对白念珠菌的抗真菌后效应（post-antifungal effect,PAFE）。结果美浮特皮肤抗菌液对4属6种57株 MIC 的范围为1：40-1：160、MIC50为1：80、MIC90为1：40;对白念珠菌的 MIC 范围为1：40-1：80、对皮肤癣菌的 MIC 范围为1：40-1：160。该抗菌液具有很强的杀菌作用,且随着药物浓度的降低,杀菌速度和程度随之变化。该抗菌液对白念珠菌0.5MIC、MIC、2MIC 的 PAFE 分别为0.85 h、2.1 h、3.59 h;且 PAFE 时间的延长与药物浓度呈正相关。结论美浮特^R皮肤抗菌液对致病真菌皮肤癣菌、白念珠菌具有快速、有效、持续的杀菌作用,该抗菌液对皮肤癣菌较白念珠菌具有更强的抗真菌作用。且该抗菌液对白念珠菌具有较长时间的后效应,可以广泛应用于临床治疗皮肤癣菌及白念珠菌所致的感染。     

Antifungal effect with apoptotic mechanism(s) of Styraxjaponoside C

The antifungal effects and mechanisms of Styraxjaponoside C were investigated. Styraxjaponoside C was active against several human pathogens, including Candida albicans. Styraxjaponoside C induced a series of cellular changes characteristic of apoptosis in C. albicans, including increased reactive oxygen species (ROS) production, measured by DHR-123 staining; phosphatidylserine externalization, visualized by Annexin V staining; DNA fragmentation, as seen by TUNEL; and plasma membrane depolarization, observed by DiBAC₄(3) staining. The plasma membrane depolarization is likely to be associated with production of ROS. The current study suggests that Styraxjaponoside C exerts an antifungal effect by promoting apoptosis.     

Antifungal activities of recombinant antifungal protein by conjugation with polyethylene glycol.

Tenecin 3, an antifungal protein isolated from coleopteran insect Tenebrio molitor larvae, inhibited growth of the fungus Candida albicans. We have previously reported that tenecin 3 has a propensity of random structure with very loose turn-like elements by circular dichroism (CD) analysis and 2D nuclear overhauser effect spectroscopy [Lee et al. (1999)]. However, the antifungal mechanism of tenecin-3 has not yet been studied due to its very low availability from natural sources. As an initial step to study the antifungal mechanism of tenecin 3, recombinant tenecin 3 (RT-3) obtained from an expression system in Escherichia coli showed antifungal activity against C. albicans as did natural tenecin 3. To elucidate the antifungal mechanism of RT-3 and to explore the possibility of preparing polyethylene glycol (PEG) conjugated derivative, we synthesized PEG conjugated RT-3 (RT-3-PEG) and examined its antifungal activity against C. albicans in vitro. RT-3-PEG showed greater antifungal activity against C. albicans than RT-3 alone at the same dose. When C. albicans was treated with RT-3-PEG in vitro, K+ in the C. albicans cell was leaked out rapidly compared to the C. albicans treated with RT-3 alone. When the morphological change of RT-3-PEG treated C. albicans was examined by scanning electron microscopy, string-like substances, which may have been derived from the fungus, were stacked around the cell whose wall was damaged. Also, no appreciable hemolysis of mouse erythrocytes was detected under conditions in which 1% melittin caused 100% hemolysis. These results suggested that the RT-3-PEG derivative probably does not interact with mammalian cell appreciably, although it has antifungal activity.     

Prophylactic use of liposomized tuftsin enhances the susceptibility of Candida albicans to fluconazole in leukopenic mice

In the present study, we investigated the immunopotentiating activity of the immunomodulator tuftsin for the treatment of dose-dependent susceptible Candida albicans infection in a murine model. Our results demonstrated that tuftsin increases the susceptibility of C. albicans to phagocytosis by activating murine macrophages. Fluconazole used for the treatment of mice infected with C. albicans showed less in vivo efficacy and proved to be ineffective in the elimination of the infection from leukopenic mice even at higher doses. However, the antifungal activity of fluconazole against the same isolate of C. albicans significantly increased in tuftsin-pretreated mice and resulted in an improved survival rate in mice. The treated mice also showed less severity of infection as supported by a reduced fungal burden in their kidneys. This study indicates that the use of immunopotentiating substances can enhance the therapeutic efficacy of azole antifungal agents and thus can effectively combat azole-resistant fungal pathogens under conditions of immunosuppression.     

Comparison between allicin and fluconazole in Candida albicans biofilm inhibition and in suppression of HWP1 gene expression

Candida albicans is an opportunistic human pathogen with the ability to differentiate and grow in filamentous forms and exist as biofilms. The biofilms are a barrier to treatment as they are often resistant to the antifungal drugs. In this study, we investigated the antifungal activity of allicin, an active compound of garlic on various isolates of C. albicans. The effect of allicin on biofilm production in C. albicans as compared to fluconazole, an antifungal drug, was investigated using the tetrazolium (XTT) reduction-dependent growth and crystal violet assays as well as scanning electron microscopy (SEM). Allicin-treated cells exhibited significant reduction in biofilm growth (p<0.05) compared to fluconazole-treated and also growth control cells. Moreover, observation by SEM of allicin and fluconazole-treated cells confirmed a dose-dependent membrane disruption and decreased production of organisms. Finally, the expression of selected genes involved in biofilm formation such as HWP1 was evaluated by semi-quantitative RT-PCR and relative real time RT-PCR. Allicin was shown to down-regulate the expression of HWP1.     

Resveratrol lacks antifungal activity against Candida albicans

The putative candicidal activity of resveratrol is currently a matter of controversy. Here, the antifungal activity as well as the antioxidant response of resveratrol against Candida albicans, have been tested in a set of strains with a well-established genetic background At the doses usually employed in antifungal tests (10-40 μg/ml), resveratrol has no effect on the exponential growth of the C. albicans CAI.4 strain, a tenfold increase (400 μg/ml) was required in order to record a certain degree of cell killing, which was negligible in comparison with the strong antifungal effect caused by the addition of amphotericin B (5 μg/ml). An identical pattern was recorded in the prototrophic strains of C. albicans SC5314 and RM-100, whereas the oxidative sensitive trehalose-deficient mutant (tps1/tps1 strain) was totally refractory to the presence of resveratrol. In turn, the serum-induced yeast-to-hypha transition remained unaffected upon addition of different concentrations of resveratrol. Determination of endogenous trehalose and catalase activity, two antioxidant markers in C. albicans; revealed no significant changes in their basal contents induced by resveratrol. Collectively, our results seem to dismiss a main antifungal role as well as the therapeutic application of resveratrol against the infections caused by C. albicans.