铜绿假单胞菌中群体感应系统的研究进展

群体感应系统(quorum sensing)是一种细菌细胞与细胞间的信号传递系统。细菌通过可扩散的小分子信号分子感知细胞群体的密度,从而引起一些特定基因在细菌群体中的协调表达。铜绿假单胞菌中的QS系统包括LasI/LasR和RhlI/RhlR两条主要的信号系统和喹诺酮信号系统。本文系统地介绍了铜绿假单胞菌中QS系统的研究现状和相关应用。     

铜绿假单胞菌的群体感应系统及其抑制剂研究进展

群体感应系统(quorum sensing system, QS)是一种微生物细胞与细胞间的交流系统。铜绿假单胞菌是该系统的典型代表,可调控细菌产生对抗生素的耐药、形成生物膜、产生毒力因子,并且减弱宿主的免疫应答。群体感应系统抑制剂(quorum sensing inhibitors, QSIs)在不影响细菌生长的前提下可降低细菌的毒性,且增强细菌生物膜对抗生素治疗的敏感性,这些特点使QSIs成为目前抗感染领域的研发热点。本文就铜绿假单胞菌的群体感应系统及QSIs的研究进展进行了综述。     

铜绿假单胞菌的群体感应系统与其致病及耐药机制

群体感应(QS)系统作为依赖细胞密度的胞间信号传递系统,在细胞生长、发育和分化中起重要作用.铜绿假单胞菌是院内常见的条件致病菌,对多种抗生素耐药.本文概述QS系统在铜绿假单胞菌致病机制及生物被膜介导的耐药机制中的作用,同时介绍基于铜绿假单胞菌QS系统的药物开发进展.     

多尼培南对铜绿假单胞菌生物被膜形成和群体感应系统的影响

目的：探究新型碳青霉烯类抗生素多尼培南（doripenem,DOR）对临床分离铜绿假单胞菌生物被膜形成的抑制作用,及对其群体感应系统相关基因LasR、RhlR、PqsA、PqsE、PqsR表达量的影响。方法：用结晶紫染色法测定30株临床分离铜绿假单胞菌形成生物被膜能力和多尼培南对生物被膜形成的抑制作用;微量肉汤稀释法测定最低抑菌浓度（minimal inhibitory concentration,MIC）和最低抑制生物被膜浓度（minimal biofilm inhibitory concentration,MBIC）;活菌计数法绘制多尼培南对生物被膜内细菌的杀菌曲线;采用实时定量荧光PCR （real-time PCR）法测定多尼培南对群体感应（quorum-sensing,QS）系统相关基因表达量的影响。结果：30株铜绿假单胞菌中的29株（97%）形成生物被膜;多尼培南具有较强的抗铜绿假单胞菌浮游菌和生物被膜抑制活性,MICR为0.5～1μg·mL-1,MBICR为1～4μg·mL-1;显著下调LasR、RhlR、PqsA、PqsE、PqsR的表达量。结论：临床分离铜绿假单胞菌具有高生物被膜形成率,多尼培南对铜绿假单胞菌生物被膜具有抑制作用,可能与其下调QS系统相关基因有关。     

铜绿假单胞菌群体感应系统及其抑制剂的研究进展

铜绿假单胞菌耐药严重,形成的感染严重威胁患者健康.群体感应是细菌密度依赖的群体调控行为.细菌利用可扩散的信号分子监控周围同种或异种细菌的密度,调控特定基因的适时、协同表达.群体感应系统参与调控铜绿假单胞菌的致病性和耐药性,备受关注.深入研究铜绿假单胞菌的群体感应系统,可阐明该菌的群体行为调控机制及致病机制,由此研发铜绿假单胞菌群体感应系统的抑制剂,对缓解该菌的耐药并根除其感染具有重要意义.本文就铜绿假单胞菌群体感应系统及其抑制剂的研究进展做一综述.     

群体感应系统对细菌耐药的调控作用

群体感应是细菌依赖于细胞密度、调节群体适应能力的一种普遍机制。细菌群体感应系统调节许多特定的功能,如对细菌耐药相关性状的调节。本文就群体感应系统对细菌耐药相关性状的调控作用进行综述。     

左氧氟沙星对铜绿假单胞菌密度感应系统及毒力因子的调控

目的：评价铜绿假单胞菌在亚抑制浓度（ SIC）的左氧氟沙星作用下毒力因子表型及基因表达的变化并探索其可能的调控途径。方法用临床标准菌株PAO1及其密度感应系统（ QS）的基因突变株,测定不同浓度下菌株生长曲线,以不影响细菌生长的最高抗菌素浓度为亚抑制浓度。分别测定各菌株在SIC的抗菌素作用下生物膜形成、绿脓菌素和鼠李糖脂的变化。用实时定量聚合酶链式反应（ RT－PCR）测定菌株毒力蛋白编码基因以及QS基因在SIC的左氧氟沙星作用下表达的变化。用生物发光法测定QS信号分子在SIC的抗菌素作用下的变化。结果在SIC的左氧氟沙星作用下,PAO1的毒力因子编码基因和QS调控基因（lasR、rhlR）表达均显著增加,PAO1野生株的毒力因子也增加,但lasR、rhlR突变株无此变化,同时QS信号分子水平也无显著变化。结论亚抑制浓度的左氧氟沙星促进铜绿假单胞菌毒力因子的产生,这一效应是通过lasR和rhlR调节实现的,但这一调控作用可能并不是直接通过AHL信号分子完成。     

原白头翁素对铜绿假单胞菌群体感应系统调控的毒力因子表达量的影响

目的 研究原白头翁素对铜绿假单胞菌(PA)的生长及群体感应系统(QS系统)调控的毒力因子表达的影响.方法 测定原白头翁素对PA的最低抑菌浓度和生长曲线,以40 μmol/L的呋喃酮C-30作为阳性对照,测定原白头翁素(40、80μmol/L)对铜绿假单胞菌标准株PA01生长曲线的影响以及QS系统调控的毒力因子中胞外3种毒力因子(绿脓菌素、蛋白水解酶和弹性蛋白酶)表达量的影响.结果 在实验所采用的浓度下,原白头翁素对铜绿假单胞菌的生长未表现出明显的抑制作用,但对PA01的3种毒力因子均有抑制作用,并呈现出剂量相关性.结论 原白头翁素抗感染的机制可能是作用于 铜绿假单胞菌的QS系统,抑制毒力因子表达,从而降低该菌的毒力.     

D-环丝氨酸抑制铜绿假单胞菌群体感应活性研究

摘要：目的 以铜绿假单胞菌模式菌株PAO1为研究对象,研究抗结核药物D-环丝氨酸通过靶向抑制病原菌群体感应 (quorum-sensing,QS)系统实现抑制病原菌毒力发挥的新应用潜力。方法 用不同浓度的D-环丝氨酸处理铜绿假单胞菌,通过 系列表型实验结合荧光定量PCR以评估D-环丝氨酸对群体感应所调节的毒力因子和相应基因表达的影响,并利用秀丽隐杆线虫 感染模型评估D-环丝氨酸对铜绿假单胞菌毒力抑制的体内活性。结果 D-环丝氨酸表现出良好的铜绿假单胞菌生物膜、绿脓菌 素以及蛋白水解酶抑制活性,显著抑制了QS系统调控基因和下游功能基因的表达,并且可以显著提高秀丽隐杆线虫在铜绿假单 胞菌感染过程的存活率。结论 D-环丝氨酸可以有效抑制铜绿假单胞菌群体感应系统,有望开发成功的抗生素替代药物。     

透明颤菌血红蛋白的研究及应用

透明颤菌血红蛋白是来自专性好氧的革兰氏阴性细菌透明颤菌属的一种同源双亚基血红蛋白,其基因的转录受生境中氧浓度的调节。当这种蛋白在多种原核及真核生物中表达时,具有促进生长和提高各种有用代谢产物的作用。证据显示该蛋白的作用机制是进行对氧的传递。     

Quorum sensing inhibitors: a patent review (2014–2018)

ABSTRACT

Introduction: Quorum sensing (QS) is a cell density-dependent phenomenon in which specific pathways are activated after autoinducers (AIs) outside the microorganism reach a threshold concentration. QS creates a positive feedback loop that induces a cascade of gene expression and causes biofilm formation, virulence and sporulation. QS signals are diverse, acyl-homoserine lactone (AHL), AI peptide (AIP) and AI-2 are three major categories of QS signals. QS inhibitors (QSIs) can disrupt or prevent the formation of biofilm and reduce virulence while exerting less selective pressure on the bacteria, suggesting that QSIs are potential alternatives for antibiotics.

Areas covered: This review summarized the pertinent patents on QS inhibition available from 2014 to 2018. The authors analyze these patents and provided an overview of them and their potential applications.

Expert opinion: The main strategy for QS inhibition is to use the analogues of various QS signals to block downstream signal transducers. The inactivation of signal molecules or the stimulation of the immune response is also attractive strategies to inhibit QS. However, additional clinical trials are needed to assess their efficacy in mammals. In sum, QS inhibition can reduce the virulence of bacteria without affecting their growth or killing them and the reduced pressure may minimize the increasingly resistance.     

Synthesis and biological activities of some 1,3-benzoxazol-2(3H)-one derivatives as anti-quorum sensing agents

Antibiotics are commonly used to treat microbial infections. Due to misuse or large-scale use of antibiotics, many pathogens have gained resistance which makes antibiotic treatments ineffective. The discovery that many bacteria use quorum sensing (QS) to regulate their virulence factor and pathogenicity production makes the QS system an attractive target for antimicrobial therapy. A series of 1,3-benzoxazol-2(3H)-one derivatives were designed and synthesized as QS inhibitors (QSIs) and tested for their QS inhibitory activities. In vitro quorum sensing inhibitor screen (QSIS) assay indicated that the 1,3-benzoxazol-2(3H)-one (compound 1), 5-chloro-1,3-benzoxazol-2(3H)-one (compound 6), 6-methyl-1,3-benzoxazol-2(3H)-one (compound 11), and 5-methyl-1,3-benzoxazol-2(3H)-one (compound 16), inhibit QS system in quorum sensing selector (QSIS)1 strain. These 4 QSIs also significantly reduced elastase production, biofilm formation and swarming motility of Pseudomonas aeruginosa PA01 strain. These results suggest that compound 1, 6, 11 and 16 may provide a starting point for the design and development of new anti-pathogenic drugs that restrict virulence of P. aeruginosa and possibly other clinically important human pathogens. In addition, these QSI molecules could potentially be used in combination with conventional antibiotics to increase the efficiency of disease control and to extend the life span of established antimicrobials.     

Small molecules for interference with cell-cell-communication systems in Gram-negative bacteria

Quorum sensing (QS) systems are bacterial cell-to-cell communication systems that use small molecules as signals. Since QS is involved in the regulation of virulence and biofilm formation in several pathogenic bacteria, it has been suggested as a new target for the development of novel antibacterial therapies. As such, interference with the signal receptors by using chemical compounds has been proposed as an alternative strategy for treatment of bacterial infections and has already shown promising results in combination with traditional antibiotic treatments. In Gram-negative bacteria, the best studied QS systems use N-acyl homoserine lactones (AHLs) as signal molecules. This review provides an overview of all new chemical structure types that inhibit AHL-mediated QS systems as reported during the last three years in scientific journals and in the patent literature. The compounds were classified into three main groups depending on their structure: AHL analogues, 2(5H)-furanones, and compounds that are not structurally related to AHLs. We discuss the biological assays used and the different strategies applied to discover these molecules, including new approaches such as molecular docking for in silico identification of lead structures and random high-throughput screening of large libraries of chemicals. Finally, we elaborate on structure-activity relationships and on the new insights in the mechanisms of action of the identified inhibitors, highlighting the potential of these small molecules in medicine.     

Design,synthesis, and a novel application of quorum-sensing agonists as potential drug-delivery vehicles

Surface adhered bacterial colonies or biofilms are an important problem in medical and food industries. Bacteria use a chemical language to monitor their quorum and to express virulence factors, which eventually help them in colonization and manifestation of an infection. The LasR-LasI and RhlR-RhlI quorum-sensing (QS) systems of Pseudomonas aeruginosa control expression of virulence factors in a population density-dependent fashion. In this study we investigated the role of synthetic analogs to RhlR-RhlI system of P. aeruginosa strains (PAO-1; wild-type and mutants JP-1, PDO-100, and JP-2) responsible for production of acyl-homoserine lactones-2; butanol homoserine lactone (AHL-2; C₄-HSL). We synthesized double (QS1207) and single (QS0108) sulfur analogs against (C₄-HSL; AHL-2), an autoinducer of Pseudomonas QS system. Extensive biological investigation of these analogs suggested a growth promoting activity for these analogs in Pseudomonas controlling biofilm production and exo-protease secretion. We hypothesized that these thiolactone analogs could be potentially utilized as potent drug-delivery vehicles against biofilm-producing pathogens. As a proof of principle we conjugated the single sulfur analog QS0108 with the broad-spectrum antibiotic, ciprofloxacin (QS0108-Cip). The QS analog-antibiotic conjugate was significantly more effective at disrupting both the nascent and mature biofilms of P. aeruginosa than the free antibiotic.     

Recent progresses on AI-2 bacterial quorum sensing inhibitors

Quorum sensing (QS) is a communication procedure that predominates gene expression in response to cell density and fluctuations in the neighboring environment as a result of discerning molecules termed autoinducers (AIs). It has been embroiled that QS can govern bacterial behaviors such as the secretion of virulence factors, biofilm formation, bioluminescence production, conjugation, sporulation and swarming motility. Autoinducer 2 (AI-2), a QS signaling molecule brought up to be involved in interspecies communication, exists in both gram-negative and -positive bacteria. Therefore, novel approaches to interrupt AI-2 quorum sensing are being recognized as next generation antimicrobials. In the present review article, we summarized recent progresses on AI-2 bacterial quorum sensing inhibitors and discussed their potential as the antibacterial agents.     

Quorum sensing inhibitors: a patent overview

Background: Quorum sensing (QS) is a microbial cell–cell signaling system that correlates gene expression with cell population density. It plays important roles in intra-species communications and is also involved in inter-species and microbe-host interactions. Because QS controls a wide spectrum of phenotypes including virulence and biofilm formation, inhibition of QS may provide alternative therapeutic methods for treating microbial infections. Objective: To provide an overview of QS inhibitors and their applications. Methods: Search of databases for patents on QS inhibition submitted between 1999 and 2008. Results/conclusions: The reported QS inhibitors include both natural and synthetic agents and can be mainly categorized in three classes: nonpeptide small molecules, peptides and proteins. These inhibitors interrupt QS by repressing signal generation, blocking signal receptors or disrupting QS signals, and provide an alternative approach to controlling microbial pathogenesis.     

Quorum sensing inhibitors: a patent review

Introduction: Quorum sensing (QS) is a cell-to-cell communication that regulates gene expression and coordinates their behavior in accordance with the cell population density as a result of discerning molecules termed autoinducers (AIs). The processes that QS governed include biofilm formation, bacterial virulence, antibiotic production, competence, conjugation, swarming motility and sporulation. Three main QS AIs are acyl-homoserine lactones, AI-2 and AI peptides. The attractive study of QS leads to an expansive number of QS inhibitors and approaches interfering with QS appearing.

Areas covered: This review summarized the recent QS inhibitor-related patents published from 2009 to 2012. The authors have analyzed these patents and have provided an overview of QS inhibitors and their application.

Expert opinion: The main strategies for QS inhibition related to the patents are disruption of the AI synthase, inactivation of the signal molecule, antagonism of the receptor and promotion of immune response to AI. Some of the natural or synthetic QS inhibitors display excellent activity to manipulate bacterial pathogenicity to offer significant potential in clinical therapy. However, more efforts are needed to be conducted to determine this form of communication to guide the development of QS inhibitors. Overall, QS is a suitable target for antimicrobial therapy and QS inhibitors are likely to lead to a renaissance of anti-virulence drugs without tolerance, which is the ultimate goal expected to achieve in this field.