MRSA的检测、耐药、流行及抗菌药物选择的研究进展

摘要：耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus，MRSA)一直以来是全世界引起感染性疾病的 重要致病菌之一。MRSA的耐药机制主要与由葡萄球菌染色体mec盒(SCCmec)上的mecA和mecC耐药基因有关。同时，在sarA系 统和agr系统等调控下细菌容易聚集形成生物膜，能有效的阻挡抗菌药物作用而产生极大的耐药性。耐药基因和生物膜的共同作 用使MRSA的耐药机制更为复杂，并在全球广泛传播，而及时准确地选择抗菌药物和检测方法显得尤为重要。本文就MRSA流 行状况、抗菌药物选择、SCCmec的基本结构与功能、MRSA耐药机制和检测方法等方面进行综述，旨在更好地为临床治疗和预 防MRSA引起的感染提供科学依据。     

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。     

细菌生物被膜相关感染的治疗进展

目的:介绍治疗细菌生物被膜相关感染方面的治疗进展.方法:根据国内外的文献资料,进行整理归纳.结果:抗菌药物主要在生物被膜形成初期有效;应用藻酸盐单克隆抗体对生物被膜相关感染进行治疗可能是一种很有前途的方法;应用藻酸盐裂解酶治疗细菌生物被膜导致的相关感染具有一定意义;此外还可以通过基因工程和改进生物医学材料的方法达到对细菌生物被膜相关感染的防治目的.结论:细菌生物被膜相关感染的防治仍是临床上的一个亟待解决的难题,但是随着对细菌生物被膜研究的不断深入,将开辟对细菌生物被膜相关感染治疗的新途径.     

铜绿假单胞菌中乙酰化褐藻胶的生物合成和功能研究进展

铜绿假单胞菌(Pseudomonas aeruginosa)是临床上三大机会致病菌之一,可导致多种急慢性感染。铜绿假单胞菌感染人体后,往往会转变成过量产生乙酰化褐藻胶的粘液型细菌,并形成生物被膜(biofilm)。一旦形成生物被膜,细菌将具有极强的抗生素耐药性和逃避机体免疫系统攻击的能力,造成临床上难治性、持续性感染。乙酰化褐藻胶是P. aeruginosa 生物被膜的主要成分,决定了生物被膜的结构与功能。因此,本文从乙酰化褐藻胶的生物合成途径及调控机制、在细菌中的生物学功能及作为抗菌药物开发靶点等几个方面进行了综述。     

儿童下呼吸道感染患者痰液耐甲氧西林金黄色葡萄球菌分离株耐药性及基因分型

目的:研究儿童下呼吸道感染耐甲氧西林金黄色葡萄球菌(MRSA)分离株的耐药性及基因分型,为临床诊疗提供参考。方法:对2009年1月-2010年12月收治的50例肺炎患儿进行临床调查,采集下呼吸道的痰液标本作细菌培养,用头孢西丁纸片法鉴定MRSA,并用琼脂稀释法测定MRSA对12种抗菌药物的最低抑菌浓度(MIC);用多重PCR方法检测MRSA的葡萄球菌染色体盒mec(SCCmec)基因分型。结果:MRSA所致的下呼吸道感染多见于低龄儿童(15 d～6岁),SCCmec基因分型中以Ⅲ型、Ⅳ型和Ⅴ型为主。所有MRSA的分离株都对青霉素和苯唑西林耐药,对万古霉素敏感,对其他抗菌药物的耐药率较高并且存在多重耐药。结论:儿童下呼吸道感染MRSA分离株多见于学龄前的儿童,SCCmec基因分型以Ⅲ型、Ⅳ型和Ⅴ型常见,MRSA对多种抗菌药物具有较高的耐药性并且存在多重耐药。     

耐甲氧西林葡萄球菌耐药机制研究

耐甲氧西林金黄色葡萄球菌(MRSA)是金黄色葡萄球菌获得甲氧西林耐药决定子-mecA基因后产生的一种高耐药性菌株,MRSA几乎对所有β-内酰胺类抗菌药物耐药,对其他类型的抗生素的耐药性逐渐上升。就MRSA的相关耐药机制进行了综述。     

耐甲氧西林金黄色葡萄球菌多重耐药性及其耐药基因的检测

金黄色葡萄菌是临床最常见的致病菌之一,在临床致病菌中分离率位居前列,其中以耐甲氧西林金黄色葡萄球菌（MRSA）尤为重要。因MRSA感染治疗困难,病死率高,引起全球关注。为了解本院MRSA耐药性及其耐药机制,为临床合理应用抗菌药物治疗提供依据,本研究对86株MRSA进行耐药性及耐药基因检测,现将结果报道如下。     

细菌生物被膜相关感染的治疗进展

细菌生物被膜(Bacterial biofilm,BBF)是细菌为适应自然环境、有利于生存而特有的生命现象.由于生物被膜相关感染疾病的治疗非常棘手,本文综述了细菌生物被膜相关感染的治疗研究进展,包括有效药物的联合应用、单克隆抗体的研制、酶学调控、基因调控、新型生物医学材料的研制等.     

我院2009-2011年铜绿假单胞菌与耐甲氧西林金黄色葡萄球菌对常用抗菌药物的耐药性变迁情况研究

目的:调查我院2009-2011年抗菌药物使用情况和铜绿假单胞菌(PA)、耐甲氧西林金黄色葡萄球菌(MRSA)的耐药性变迁趋势,分析PA和MRSA的耐药性变迁与抗菌药物使用强度(AUD)之间的关系。方法:收集我院2009-2011年PA和MRSA菌株的检出率及耐药率、常用抗菌药物使用记录,以限定日剂量(DDD)为单位计算抗菌药物的AUD,并对相关数据进行回顾性分析比较。结果:3年中PA和MRSA痰标本所占比例最高;PA和MRSA的耐药机制复杂,对大多数抗菌药物耐药且耐药性呈上升趋势;在PA和MRSA的临床应用中,除天然耐药外,多数抗菌药物的AUD高低均会对其耐药性产生影响,抗菌药物的用量越多、时间越长或滥用,都会导致细菌的耐药率增高。结论:控制细菌耐药性的关键在于对药物的合理使用。应暂停使用耐药率高的抗菌药物,待其敏感性上升后再恢复使用;或者有计划地、科学地将抗菌药物分批、分期替换使用,以减缓耐药菌株的产生。     

低频超声与抗菌药物协同增效研究进展

细菌耐药日益严重,单一抗菌药物难以完全杀灭耐药菌。应用低频超声技术联合抗菌药物,无论是对于浮游态菌还是生物被膜态菌,都能增强抗菌药物的杀菌或抑菌作用。其机制主要为空化效应。目前,低频超声技术已探索性应用于人体局部感染治疗中。作为一种可靶向治疗的非侵入性疗法,低频超声具有很大的临床应用潜能。此外,低频超声技术在基因转染上具有优势,并可通过改变基因来影响细菌耐药性。     

耐甲氧西林金葡菌的分子分型、毒力因子及生物膜研究

目的 研究耐甲氧西林金黄色葡萄球菌(MRSA)的标本分布、耐药情况、SCCmec、spa分型、相关毒力因子及生 物膜形成情况。方法 采用多重PCR扩增SCCmec、spa基因及毒力因子(tst、lukE、pvl、fnbA、fnbB、cna、clfA、clfB)；采用 Sanger双脱氧链终止法对扩增产物测序；采用微孔结晶紫染色法研究菌株生物膜形成。结果 标本来源以分泌物最多，其次是 痰；标本分布以儿童病区最多，其次为创伤病区及重症监护病区；SCCmec分型显示I型最多，占56%；spa分型以t437最多，占 43%；多数菌株同时携带3种及以上毒力因子，以cna、fnbB和clfA黏附分子为主；60%的MRSA菌株具有较强生物膜形成能力。 结论 MRSA在儿童病房的流行需要引起注意；ICU病区呼吸机引起的相关感染仍是一大难题。本医疗机构内MRSA(2018— 2019年)菌株以t437-SCCmecI型为主要流行克隆株。MRSA携带黏附毒素比率高，容易形成生物被膜，成为治疗的一大难题。     

Advances in MRSA drug discovery: where are we and where do we need to be?

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) have been on the increase during the past decade, due to the steady growth of the elderly and immunocompromised patients, and the emergence of multidrug-resistant (MDR) bacterial strains. Although there are a limited number of anti-MRSA drugs available, a number of different combination antimicrobial drug regimens have been used to treat serious MRSA infections. Thus, the addition of several new antistaphylococcal drugs into clinical practice should broaden clinician's therapeutic options. As MRSA is one of the most common and problematic bacteria associated with increasing antimicrobial resistance, continuous efforts for the discovery of lead compounds as well as development of alternative therapies and faster diagnostics are required.

Areas covered: This article summarizes the FDA-approved drugs to treat MRSA infections, the drugs in clinical trials, and the drug leads for MRSA and related Gram-positive bacterial infections. In addition, the article discusses the mode of action of antistaphylococcal molecules and the resistant mechanisms of some molecules.

Expert opinion: The number of pipeline drugs presently undergoing clinical trials is not particularly encouraging. There are limited and rather expensive therapeutic options for MRSA infections in the critically ill. Further research efforts are required for effective phage therapy on MRSA infections in clinical use, which seem to be attractive therapeutic options for the future.     

Hyicin 4244, the first sactibiotic described in staphylococci,exhibits an anti-staphylococcal biofilm activity

Hyicin 4244 is a small antimicrobial peptide with a broad spectrum of activity that was found in the culture supernatant of Staphylococcus hyicus 4244, the genome of which was then sequenced. The bacteriocin gene cluster (hyiSABCDEFG) was mined from its single chromosome and exhibited a genetic organization similar to that of subtilosin A. All genes involved in hyicin 4244 biosynthesis proved to be transcribed and encode proteins that share at least 42% similarity to proteins encoded by the subtilosin A gene cluster. Due to its resemblance to subtilosin A and the presence of three thioether bonds in its structure, hyicin 4244 is assumed to be a 35–amino acid circular sactibiotic, the first to be described in staphylococci. Hyicin 4244 inhibited 14 staphylococcal isolates from either human infections or bovine mastitis, all biofilm formers. Hyicin 4244 significantly reduced the number of colony–forming units (CFU) and the biofilm formation by two strong biofilm-forming strains randomly chosen as representatives of the strains involved in human infections and bovine mastitis. It also reduced the proliferation and viability of sessile cells in established biofilms. Therefore, hyicin 4244 proved not only to prevent biofilm formation by planktonic cells, but also to penetrate the biofilm matrix in vitro, exerting bactericidal activity against staphylococcal sessile cells. This bacteriocin has the potential to become an alternative antimicrobial for either prevention or treatment of biofilm-related infections caused by different staphylococcal species.     

Antibacterial effect of tea-tree oil on methicillin-resistant Staphylococcus aureus biofilm formation of the tympanostomy tube: an in vitro study

The antibacterial effects of tea-tree oil against the formation of methicillin-resistant Staphylococcus aureus (MRSA) biofilm on the surface of the tympanostomy tubes was evaluated. MATERIALS AND METHODS: Silicone tympanostomy tubes were pretreated with normal saline for 12 hours, the control group (n=4), with 100% tea-tree oil, experimental group A (n=3), or with 50% tea-tree oil, experimental group B (n=3). All the tubes were incubated in a MRSA solution for 2 days and then processed for evaluation using scanning electron microscopy. RESULTS: The development of the biofilm mode of growth of MRSA was observed in the saline-treated control group. In contrast, only focal biofilms were present on the tube surface in experimental group A and considerable reduction of biofilm with destruction of the MRSA cells was shown in experimental group B. CONCLUSION: From these results, the antimicrobial effect of tea-tree oil against biofilm formation on tympanostomy tubes in vitro has been verified.     

草决明与苯唑青霉素联用对临床MRSA菌株的杀菌作用研究

目的观察草决明醇提液对临床MRSA菌株生物膜形成的影响及其与苯唑青霉素联用对MRSA菌株的杀菌作用。方法构建生物膜形成阳性菌株,96孔板法测定草决明醇提液及苯唑青霉素对临床MRSA菌株生物膜形成的影响,棋盘法测定草决明与苯唑青霉素联用对临床MRSA菌株的杀菌作用。结果亚抑菌浓度的草决明醇提液可抑制临床MRSA菌株生物膜的形成,与苯唑青霉素联用对临床MRSA菌株杀菌作用有协同作用。结论草决明与苯唑青霉素联用时有协同杀菌作用,此作用可能与草决明醇提液抑制金葡菌生物膜形成有关。     

Effects of sub-minimum inhibitory concentrations of antimicrobial agents on Streptococcus mutans biofilm formation

Many studies have demonstrated that sub-minimum inhibitory concentrations (sub-MICs) of antimicrobial agents can inhibit bacterial biofilm formation. However, the mechanisms by which antimicrobial agents at sub-MICs inhibit biofilm formation remain unclear. At present, most studies are focused on Gram-negative bacteria; however, the effects of sub-MICs of antimicrobial agents on Gram-positive bacteria may be more complex. Streptococcus mutans is a major cariogenic bacterium. In this study, the S. mutans growth curve as well as the expression of genes related to S. mutans biofilm formation were evaluated following treatment with 0.5× MIC of chlorhexidine (CHX), tea polyphenols and sodium fluoride (NaF), which are common anticaries agents. The BioFlux system was employed to generate a biofilm under a controlled flow. Morphological changes of the S. mutans biofilm were observed and analysed using field emission scanning electron microscopy and confocal laser scanning microscopy. The results indicated that these three common anticaries agents could significantly upregulate expression of the genes related to S. mutans biofilm formation, and S. mutans exhibited a dense biofilm with an extensive extracellular matrix following treatment with sub-MICs of NaF and CHX. These findings suggest that sub-MICs of anticaries agents favour S. mutans biofilm formation, which might encourage dental caries progression.     

In vitro activity of RBx 7644 (ranbezolid) on biofilm producing bacteria

Biofilm associated infections are becoming more common. Treatment outcome of device related infections cannot be predicted by the results of a standard susceptibility test such as the MIC. Microorganisms involved in device related infections have a slow growth rate and adhere to surfaces. Activity against glass adherent bacteria has been shown to be correlated with treatment outcome in animal models of catheter related infections. Drug efficacy can be predicted if glass adherent staphylococci are killed by low drug concentration. The eradication of bacteria adhering to glass beads and inhibition of biofilm formation by ranbezolid and three other antibiotics (quinupristin/dalfopristin, vancomycin and linezolid) was studied. The results indicated that ranbezolid required only (2-4 x MIC) for total clearance of glass-adherent MRSA 562 and MRSE 879, compared with vancomycin (8 x), quinupristin/dalfopristin (1-4 x) and linezolid (4-16 x MIC). In addition ranbezolid inhibited biofilm formation to a greater extent at sub MIC and MIC level. In conclusion, this study indicated that ranbezolid had potent activity against adherent staphylococci isolates and may prove useful in the prevention and treatment of device related infections caused by staphylococci.     

Candida biofilm resistance.

Device-related infections in most nosocomial diseases can be traced to the formation of biofilms (microbial communities encased within polysaccharide-rich extracellular matrix) by pathogens on surfaces of these devices. Candida species are the most common fungi isolated from these infections, and biofilms formed by these fungal organisms are associated with drastically enhanced resistance against most antimicrobial agents. This enhanced resistance contributes to the persistence of this fungus despite antifungal therapy. Candida biofilms exhibit enhanced resistance against most antifungal agents, except echinocandins and lipid formulations of AmB. The expression of drug efflux pumps during the early phase of biofilm formation and alterations in membrane sterol composition contribute to resistance of these biofilms against azoles. Metabolic dormancy and ECM do not appear to contribute to resistance, although in a mixed-species biofilm, ECM does retard the diffusion of drugs across biofilm. These multifactorial mechanisms of resistance in fungal biofilms constitute a broad-spectrum defense that is effective against many types of antifungal agents, and represent a common theme present across microbial biofilms.