白假丝酵母菌生物膜的研究进展

随着医疗水平的不断发展,越来越多的医疗操作、医疗设备和药物可能导致人体正常的微生物平衡被打破,使得机会致病菌白假丝酵母菌的感染呈现逐年上升的趋势。白假丝酵母菌在宿主或医疗器械表面形成生物膜的能力是一个十分关键的毒力因素。生物膜可以帮助白假丝酵母菌成功逃避宿主免疫并产生较强的耐药性,从而导致难治性真菌感染。本文从白假丝酵母菌生物膜的形成过程、生物膜相关的主要基因和影响生物膜毒力的因素3个方面介绍近年来的研究进展,为进一步研究白假丝酵母菌生物膜的形成机制提供参考。     

阴道白假丝酵母菌水解酶的研究进展

外阴阴道白假丝酵母菌病是常见的妇产科感染性疾病,对其致病微生物白假丝酵母菌的研究方向已从大范围的筛查病因过渡到小范围的深入研究,本文系统综述了近年来对白假丝酵母菌水解酶的研究发现和前沿进展。     

白假丝酵母菌毒力相关的RAPD条带的克隆及其生物信息学分析

[目的]研究与白假丝念珠菌毒力相关的RAPD电泳条带的基因信息,明确这些条带是否来源于已知的毒力调控基因。[方法]通过对相关的白假丝酵母菌重新进行RAPD-PCR,切胶回收,以回收的DNA作为模板进行大量扩增,构建TA克隆,送测序。将获得的DNA信息登录Gen Bank数据库进行比对,寻找与包含这些条带信息的蛋白质。查阅文献,进行生物信息学分析,明确条带的基因信息与已发现的白假丝酵母菌调控基因之间的关系。[结果]白假丝酵母菌RAPD的450 bp条带为Abp1p(ABP1)蛋白的基因片段。[结论]Abp1p(ABP1)基因的过表达可能与下调磷脂酶表达有关,但具体机制有待进一步研究。     

白假丝酵母菌耐药与抗氰呼吸的相关性研究

目的探讨白假丝酵母菌的耐药情况及其与抗氰呼吸的相关性。方法用真菌药敏测定试剂盒测定从临床分离出来的37株白假丝酵母菌的耐药性,并从中选出5株耐药菌和5株敏感菌进行抗氰呼吸的研究。结果白假丝酵母菌对益康唑的耐药率最高,达54.1%,耐药白假丝酵母菌的抗氰呼吸速率均值为(17.56±6.75)nmol/(min.A620),敏感白假丝酵母菌的抗氰呼吸速率均值为(7.99±5.80)nmol/(min.A620),耐药白假丝酵母菌的抗氰呼吸速率明显升高,且耐药菌株抗氰呼吸速率占总呼吸的比例明显高于敏感菌株(P0.05),差异具有显著性。结论兰州市区白假丝酵母菌对益康唑耐药性较高,且白假丝酵母菌的耐药与抗氰呼吸途径相关。     

白假丝酵母菌体外生物膜药敏性不同检测方法的比较

目的比较不同的方法对白假丝酵母菌体外生物膜药敏性检测的差异。方法分别采用菌落计数法(CFU)、AlamarBlue试剂法、XTT减低法、MTT法对白假丝酵母菌体外48h成熟生物膜的药敏性进行检测,并将AlamarBlue试剂法、XTT减低法、MTT法与CFU法进行比较,观察其相关性及差异性。结果 AlamarBlue试剂法、XTT减低法、MTT法与CFU法都有较高的相关性,相关系数分别为r=0.969、r=0.971、r=0.982(P0.01);与CFU法的差异分别为(0.093±0.127)、(0.054±0.113)、(0.013±0.066),其差异无统计学意义(P0.05)。结论 AlamarBlue试剂法、XTT减低法、MTT法均可替代CFU法对白假丝酵母菌生物膜进行药敏检测。MTT法与CFU法的相关性最大,差异性最小;AlamarBlue试剂作为一种新的试剂,操作简单,对细胞及人类无毒害,更加适合高通量检测。     

耐氟康唑的白假丝酵母菌主动外排机制初探

目的:了解对氟康唑耐药的白假丝酵母菌主动外排系统及主动外排基因CDR1的表达水平。方法:检测氟康唑敏感性和耐药性白假丝酵母菌对罗丹明6G主动外排情况,筛选出主动外排系统功能增强的菌株;采用Northern blot技术检测主动外排系统功能增强的菌株的CDR1基因的表达。结果:在由葡萄糖提供能量的体系中,5株耐药菌株外排罗丹明6G较敏感菌株明显增加,Northern blot发现其中4株CDR1基因表达水平升高。结论:耐氟康唑白假丝酵母菌主动外排基因CDR1表达升高。     

呼吸道感染中白假丝酵母菌的致病性与细胞外水解酶关系

将84株呼吸道分离的白假丝酵母菌分为致病组和非致病组,采用卵黄培养基法检测细胞外磷脂酶的活力,用牛血清白蛋白琼脂培养基法检法分泌型天冬氨酸蛋白酶的活力,并用RT-PCR的方法检测这2种酶相关基因PLB1和SAP2的表达情况,分析其组间差别,结果表明致病组菌株的分泌型天冬氨酸蛋白酶的活力要高于非致病组(P=0.034<0.05),细胞外磷脂酶活力二组未见差别,致病组的PLB1和SAP2基因的表达均高于非致病组(P<0.05),PLB1和SAP2的表达存在着明显的正相关(r=0.776,P<0.01),提示分泌型天冬氨酸蛋白酶是呼吸道白假丝酵母菌重要的毒力因子,PLB1和SAP2的表达上调可能影响菌株的毒力,这2个基因的表达量有正相关的关系。     

应用流式细胞术对白假丝酵母菌耐药机制的研究

目的 探讨流式细胞术研究白假丝酵母菌耐药机制的可行性.方法 临床分离对氟康唑敏感的白假丝酵母菌种,经体外诱导产生耐药.应用荧光染料PI(碘化丙啶)和罗丹明123染色,通过流式细胞术检测敏感株、耐药株、回复敏感株的细胞周期和药物外排活性.结果 与敏感株和回复敏感株比较,耐药株增殖活性明显下降,但是药物外排活性显著增强.结论 应用氟康唑能够体外诱导白假丝酵母菌产生耐药.流式细胞术应用于白假丝酵母菌增殖活性和药物外排活性研究是可行的.     

胶体纳米银对白假丝酵母菌的抑制作用

目的 探讨胶体纳米银对白假丝酵母菌的抑制作用。方法 以白假丝酵母菌为研究对象,采用倍比稀释及涂布法,检测胶体纳米银对白假丝酵母菌的抑制作用及影响因素。结果 化学纳米银及物理纳米银对白假丝酵母菌的最小抑菌浓度及最小杀菌浓度相同,分别为3.13 μg/mL和6.25 μg/mL。12.50 μg/mL的化学纳米银及物理纳米银可在5 min内完全杀死白假丝酵母菌。胶体纳米银的抑菌作用受到杀菌环境的影响,特别氯离子对胶体纳米银的杀菌作用有明显的影响。结论 胶体纳米银对白假丝酵母菌具有明显的抑菌作用,其抑制作用易受到氯离子及蛋白质的的影响。     

阴道白假丝酵母菌过度增殖的小鼠模型建立

目的建立阴道白假丝酵母菌过度增殖的小鼠模型。方法甲硝唑溶液（浓度为12．5mg／mL）30μL注入小鼠阴道内,1次／d,连续5d,白假丝酵母菌菌液（1×10^8CFU／mL）30μL接种到小鼠阴道内,1次／d,连用5d。取阴道冲洗液进行阴道菌群分析,并做阴道组织标本电镜观察。结果模型组小鼠阴道内白假丝酵母菌活菌数显著增加,乳杆菌活菌数量显著下降（P〈0．01）,出现阴道红肿、分泌物多和黏膜充血等白假丝酵母菌过度增殖的典型症状。结论通过抗生素脱污染后,小鼠阴道内接种白假丝酵母菌,能在小鼠阴道内定植,成功建立阴道白假丝酵母菌过度增殖的小鼠模型。     

白念珠菌生物被膜形成的遗传调控机制

白念珠菌是人体重要的条件性致病真菌。形态的多样性和可塑性是白念珠菌典型的生物学特征,这与它的致病性、宿主适应能力以及有性生殖过程密切相关。白念珠菌生物被膜(Biofilm)是由不同形态细胞(包括酵母型、菌丝和假菌丝)以及胞外基质组成的致密结构,也是毒性和耐药性形成的重要因子。生物被膜对抗真菌药物、宿主免疫系统和环境胁迫因子等都表现出较强的抵抗力和耐受性,是临床上病原真菌感染防治的重大挑战。随着基因表达谱和遗传操作技术的发展,白念珠菌生物被膜的形成及其耐药性的获得所依赖的遗传调控通路和分子调控机制越来越清楚。主要包括MAPK和cAMP介导的信号途径以及Bcr1和Tec1等因子介导的转录调控。此外,白念珠菌生物被膜的形成与形态转换和有性生殖之间存在密切的联系。文中综述了白念珠菌生物被膜形成的遗传调控机制,重点介绍了细胞壁相关蛋白、转录因子和交配型对该过程的调控以及生物被膜的耐药机制。     

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.     

抗白念珠菌生物被膜药物的研究进展

白念珠菌是临床最常见的一种能产生生物被膜的致病真菌,所产生的生物被膜是导致高度耐药性和临床白念珠菌反复感染的直接原因.近年来,科学家们开始关注天然产物的抗生物被膜活性,以及不同药物联合应用的抗生物被膜效果,该文对抗白念珠菌生物被膜药物的研究进展作一综述.     

白念珠菌破壁方法的研究应用进展

细胞壁作为真菌中特殊和必须的细胞结构,相对于哺乳动物的细胞膜更加坚硬,难以用简单的方法使其充分破碎。因此,达到理想的破壁效果是白念珠菌研究中的关键步骤之一。在提取白念珠菌RNA、DNA和蛋白质等细胞组分的过程中,为获得足量和稳定的实验样品。该文对多种白念珠菌破壁方法作一综述,以便为白念珠菌相关研究提供适用、高效的破壁方案。     

大蒜素对白色念珠菌生物被膜形成的作用

生物被膜的形成是白色念珠菌产生耐药性的重要原因之一。本研究首先构建白色念珠菌体外生物被膜模型,通过倒置显微镜和甲基四氮盐（XTT）法检测大蒜素对白色念珠菌生物被膜形成的影响,同时采用实时荧光定量PCR法（qRT-PCR）对白色念珠菌生物被膜相关基因ALS1、ALS3、HWP1、MP65、SUN41的表达水平进行检测。结果显示,当大蒜素浓度≥12.5μg/mL时,白色念珠菌生物被膜的生长被抑制,并且在生物被膜形成的早期,大蒜素干预能有效抑制其形成;大蒜素能下调白色念珠菌生物被膜相关基因ALS1、ALS3、HWP1、MP65、SUN41的表达水平。研究结果提示,大蒜素可有效抑制体外白色念珠菌生物被膜的形成,可能与其下调生物被膜相关基因的表达有关。     

Pathways to acetyl-CoA formation in Candida albicans

The supply of acetyl units from the mitochondrion to the cytosol of Candida albicans appears to be dependent only upon the activity of carnitine acetyltransferase (CAT). The enzyme ATP:citrate lyase (ACL), the major source of acetyl units in oleaginous yeasts, is absent from C. albicans in both the mycelial and yeast forms. There appears to be no other active translocation of acetate or acetyl groups except via the action of carnitine acetyltransferase.     

Interspecific hybridisation between Candida albicans and Candida tropicalis

Abstract Protoplasts from auxotrophic mutants of Candida albicans and Candida tropicalis were produced by snail enzyme treatment and their fusion was induced with polyethylene glycol (PEG). During selective regeneration, nutritionally complemented interspecific hybrids were obtained. Their cells contained one nucleus, and the DNA content per cell was higher than in the parents. The isoenzymic and sugar assimilation patterns of the mutants, and those of the hybrids and the products after their haploidisation, were also analysed. The results indicated that the hybrids were partial alloploids containing the total chromosomal set of either of the parental species and one or a few chromosomes of the other.     

Azole sensitivity in Candida albicans

Abstract In the present study, we assessed the influence of three culture media on the susceptibility 'in vitro' of twenty four clinical strains belonging to Candida albicans against three imidazole-derivatives and also, we investigated the situation of azole sensitivity in three of these strains.     

Comparison of the epidemiology, drug resistance mechanisms, and virulence of Candida dubliniensis and Candida albicans

Candida dubliniensis is a pathogenic yeast species that was first identified as a distinct taxon in 1995. Epidemiological studies have shown that C. dubliniensis is prevalent throughout the world and that it is primarily associated with oral carriage and oropharyngeal infections in human immunodeficiency virus (HIV)-infected and acquired immune deficiency syndrome (AIDS) patients. However, unlike Candida albicans, C. dubliniensis is rarely found in the oral microflora of normal healthy individuals and is responsible for as few as 2% of cases of candidemia (compared to approximately 65% for C. albicans). The vast majority of C. dubliniensis isolates identified to date are susceptible to all of the commonly used antifungal agents, however, reduced susceptibility to azole drugs has been observed in clinical isolates and can be readily induced in vitro. The primary mechanism of fluconazole resistance in C. dubliniensis has been shown to be overexpression of the major facilitator efflux pump Mdr1p. It has also been observed that a large number of C. dubliniensis strains express a non-functional truncated form of Cdr1p, and it has been demonstrated that this protein does not play a significant role in fluconazole resistance in the majority of strains examined to date. Data from a limited number of infection models reflect findings from epidemiological studies and suggest that C. dubliniensis is less pathogenic than C. albicans. The reasons for the reduced virulence of C. dubliniensis are not clear as it has been shown that the two species express a similar range of virulence factors. However, although C. dubliniensis produces hyphae, it appears that the conditions and dynamics of induction may differ from those in C. albicans. In addition, C. dubliniensis is less tolerant of environmental stresses such as elevated temperature and NaCl and H(2)O(2) concentration, suggesting that C. albicans may have a competitive advantage when colonising and causing infection in the human body. It is our hypothesis that a genomic comparison between these two closely-related species will help to identify virulence factors responsible for the far greater virulence of C. albicans and possibly identify factors that are specifically implicated in either superficial or systemic candidal infections.     

Candida albicans biofilm formation on peptide functionalized polydimethylsiloxane

In order to prevent biofilm formation by Candida albicans, several cationic peptides were covalently bound to polydimethylsiloxane (PDMS). The salivary peptide histatin 5 and two synthetic variants (Dhvar 4 and Dhvar 5) were used to prepare peptide functionalized PDMS using 4-azido-2,3,5,6-tetrafluoro-benzoic acid (AFB) as an interlinkage molecule. In addition, polylysine-, polyarginine-, and polyhistidine-PDMS surfaces were prepared. Dhvar 4 functionalized PDMS yielded the highest reduction of the number of C. albicans biofilm cells in the Modified Robbins Device. Amino acid analysis demonstrated that the amount of peptide immobilized on the modified disks was in the nanomole range. Poly-d-lysine PDMS, in particular the homopeptides with low molecular weight (2500 and 9600) showed the highest activity against C. albicans biofilms, with reductions of 93% and 91%, respectively. The results indicate that the reductions are peptide dependent.