主动外排系统介导细菌对替加环素产生耐药的机制研究进展

目的:综述国内外在主动外排系统介导细菌产生替加环素耐药机制方面的最新研究进展。方法:通过查阅美国国立医学图书馆和中国知网学术期刊全文数据库,以"替加环素""耐药"等为关键词,使用布尔逻辑算符"and"进行检索,收集从2004-2013年以来有关主动外排系统介导细菌产生替加环素耐药机制的研究文献进行归纳。结果:主动外排系统在细菌产生替加环素耐药的机制中占重要地位,参与耐药形成的外排泵家族包括耐药节结化细胞分化(RND)家族、多药及毒性化合物外排(MATE)家族与主要易化子(MFS)超家族。在医院常见的革兰阴性耐药菌如大肠埃希菌、鲍曼不动杆菌、铜绿假单胞菌中,RND家族外排泵是介导上述细菌产生替加环素耐药性的主要原因;在革兰阳性致病菌中,MATE家族参与替加环素耐药性的产生;而主要MFS超家族中的TetA外排泵仅介导沙门氏菌对替加环素的耐药性。结论:细菌对替加环素耐药的现象有增多趋势,临床上应慎重、合理地使用替加环素;主动外排系统在细菌产生替加环素耐药的机制中占关键地位,进一步研发外排泵抑制剂,可遏制细菌对替加环素耐药的发生。     

不动杆菌对替加环素及多黏菌素耐药机制研究进展

不动杆菌属细菌是临床常见的非发酵糖菌,广泛分布于医院环境中,是引起多种院内感染的重要条件致病菌.随着临床抗菌药物的大量使用,不动杆菌逐渐出现了多重耐药甚至全耐药株,有效抗菌药物极少,给临床感染的治疗带来极大困难.近年来发现替加环素和多黏菌素治疗多重耐药革兰阴性菌感染特别是鲍曼不动杆菌有较好疗效,但随着研究的不断深入,逐渐发现不动杆菌对替加环素及多黏菌素也存在耐药性,本文就目前国内外不动杆菌对替加环素及多黏菌素耐药机制进行简要综述.不动杆菌对替加环素耐药机制主要与AdeABC外排泵系统有关,对多黏菌素的耐药机制主要为外膜LPS修饰.还需要针对不动杆菌对替加环素及多黏菌素的耐药机制进一步研究,从而指导临床合理使用抗菌药物.     

鲍曼不动杆菌8种RND外排泵介导替加环素耐药表型的研究

目的 探讨鲍曼不动杆菌中8种RND外排泵基因的分布与替加环素耐药表型间的关系。方法 微量肉汤稀释法检测120株鲍曼不动杆菌对替加环素的耐药性,PCR扩增8种外排泵及调控基因。琼脂二倍稀释法测定替加环素耐药菌株对18种抗菌药物的最低抑菌浓度(minimal inhibitory concentration, MIC),利用5种外排泵抑制判定外排泵表型。采用实时荧光定量PCR检测外排泵基因的表达水平。结果 筛选出替加环素耐药菌8株,对18种抗菌药物耐药情况严重,其中6株为广泛耐药菌;3种外排泵抑制剂CCCP、PAβN及维拉帕米的表型阳性率分别为50%、37.5%和12.5%。耐替加环素菌株除ACICU_02904和ACICU_03412基因外均为阳性;替加环素敏感菌中外排泵(adeABC-adeRS、adeFGH-adeL和adeIJK-adeN)基因检测率为38.4%,新近发现外排泵(ACICU_00143、ACICU_03066和ACICU_03646)基因检测率为50.9%,然而,ACICU_02904和ACICU_03412基因检出率为0.9%。在转录水平上,替加环素耐药组的adeB相对表达量是敏感组的23.5倍。结论 鲍曼不动杆菌中adeB相对表达量伴随菌株对替加环素MIC值增加而升高,主动外排泵表达活性增加是替加环素耐药的一个重要机制。     

ADR风向标

近年来,临床抗感染治疗面临的挑战不断增加。由多重耐药菌（MDRO）引起的院内感染严重影响了医疗安全和患者安全。替加环素作为新近上市的抗菌药,能克服常见的外排泵和核糖体保护等细菌耐药机制,不易产生耐药性。然而最近FDA发出一项警告,声称这款药物会增加患者的死亡风险。     

细菌外排泵介导耐药性研究进展

随着抗生素的广泛应用,临床上产生一些多重耐药菌株。多重耐药菌株的产生使常规抗生素在临床细菌性感染治疗中失效。细菌主动外排是耐药菌株产生多重耐药的主要机制之一;因此有关细菌主动外排泵的研究也是近年来细菌多重耐药机制研究中,相对较新和活跃的领域。本文结合当前主动外排泵研究的进展,对主动外排蛋白的分类、组成和主要的主动外排系统的基因表达调控以及耐药性情况进行综述。     

抗替加环素鲍曼不动杆菌耐药机制的研究进展

鲍曼不动杆菌是临床常见的条件致病菌,广泛分布于医院环境中,常导致患者出现血流、呼吸道、泌尿生殖道及中枢神经系统感染。作为一种新型的四环素类抗菌药物,替加环素对鲍曼不动杆菌尤其是泛耐药鲍曼不动杆菌具有很好的疗效,但其耐药性也日趋严重。流行病学研究发现,鲍曼不动杆菌对替加环素的耐药性呈现出显著的地区性差异。相关基础研究表明,其耐药机制主要与AdeABC外排泵系统的过表达有关。结合近期的研究结果,本文就耐替加环素鲍曼不动杆菌的流行病学现状和耐药机制进行简要综述。     

临床分离铜绿假单胞菌对碳青霉烯类药物的耐药机制

目的研究临床分离的铜绿假单胞菌对碳青酶烯类抗菌药物的耐药机制。方法测定临床分离的铜绿假单胞菌对亚胺培南、美洛培南、帕尼培南、头孢他啶、环丙沙星、米诺环素的体外抗菌活性；从中选取不同耐药表型菌株8株，以标准株PAOI为对照，凝胶电泳分析外膜蛋白；用荧光定量RT-PCR测定细菌主动外排系统结构mexA、mexC和mexE的表达，并对其调控基因进行测序。结果3株细菌金属酶测定阳性；敏感菌株与PAOI外膜蛋白图谱相似，耐药菌株尤其是对亚胺培南耐药株OprD2量减少或消失；随着细菌耐药性增强，主动外排系统表达逐渐增加。5株细菌发现mexR，nfxB突变。结论外膜蛋白D2缺失、主动外排系统表达增加、产生碳青霉烯酶是铜绿假单胞菌对碳青霉烯类耐药的主要机制；但细菌对不同药物耐药机制存在一定差异。     

替加环素对临床常见多重耐药菌的体外抗菌活性分析

目的:分析替加环素对临床常见多重耐药菌的体外抗菌活性.方法:我院2013年8月～2015年12月检验室采用微量肉汤稀释法检测经替加环素分离的400株多重耐药菌.多重耐药菌中包括金黄色葡萄球菌、鲍曼不动杆菌、肠球杆菌等细菌的最小抑菌浓度,并与其他菌种的药物进行分析比较.结果:金黄色葡萄球菌、肠球菌属细菌、鲍曼不动杆菌与肠杆菌属细菌对替加环素耐药性、敏感性与使用最低浓度均显著优于氨苄西林、头孢曲松、米诺环素(P＜0.05).结论:替加环素抗生素类药物对革兰氏阴性菌及革兰氏阳性菌2种多重耐药菌均具有较佳的体外抑菌活性.     

替加环素抗耐药菌作用的研究进展

目的：了解替加环素对多重耐药菌的抗菌活性,为临床合理使用替加环素治疗多重耐药菌感染提供参考。方法：搜集国内、外有关替加环素抗耐药菌作用及应用的文献,进行文献综述。结果：替加环素对临床各种多重耐药菌株,如耐甲氧西林金黄色葡萄球菌（MRSA）、耐万古霉素肠球菌（VRE）、耐青霉素肺炎链球菌（PRSP）、耐碳青霉烯肺炎克雷伯菌以及泛耐药鲍曼不动杆菌等有良好的抗菌活性及临床疗效。结论：替加环素具有较强的抗耐药菌活性,在多重耐药菌感染治疗中可考虑合理应用。     

苦参碱逆转外排泵系统AcrAB-ToIC介导的耐碳青霉烯类肺炎克雷伯菌对替加环素的耐药性

目的 评估苦参碱对由外排泵AcrAB-TolC介导的耐碳青霉烯类肺炎克雷伯菌对替加环素耐药的影响并探究其逆转耐药性的相关调控机制。方法 使用棋盘稀释法，分别设置阴性对照组、阳性对照组、替加环素组、苦参碱组、联合用药组；培养24 h后，酶标仪测定吸光度，记录各药物组的最低抑菌浓度(MIC)、计算抑菌率和部分抑菌浓度指数(FIC);取各药物组MIC对应孔和阳性对照孔，使用实时荧光定量聚合酶链式反应(PCR)技术检测AcrAB-TolC外排泵系统调控基因AcrB、MarA、RamA、AcrR的表达情况。结果 与单用替加环素或苦参碱相比较，替加环素与苦参碱联合应用能更明显的抑制外排泵系统AcrAB-TolC介导的替加环素耐药的耐碳青霉烯类肺炎克雷伯菌的生长(P<0.05),替加环素与苦参碱的药理主要表现为协同或相加作用；联合用药下，替加环素与苦参碱的MIC值均明显降低，替加环素的MIC均能恢复至替加环素敏感MIC值；苦参碱单独或联合作用后，AcrAB-TolC外排泵RamA、AcrB表达明显降低(P<0.05),AcrR基因表达明显升高(P<0.05)。结论 苦参碱能下调耐碳...     

Development mechanism of resistant population post-exposure to tigecycline in tigecycline-heteroresistant Acinetobacter baumannii strain

Tigecycline heteroresistance is highly prevalent in Acinetobacter baumannii clinical isolates, reducing the efficacy of tigecycline treatment. This study investigated the population dynamics of A. baumannii with tigecycline heteroresistance to determine the origin of resistance that occurs over time after antibiotic exposure. Tigecycline heteroresistance was imitated by mixing tigecycline-susceptible and -resistant A. baumannii isolates in a 1:10^?6 ratio, and confirmed using population analysis profiling. Growth curves and an in-vitro competition assay found no difference in bacterial fitness between tigecycline-resistant and -susceptible populations. The green fluorescent protein (GFP) expression system and flow cytometry were used to monitor the population dynamics of the heteroresistant population, while differentiating the resistant population from the susceptible population. The mimicked tigecycline heteroresistance was confirmed to be reproducible and stable without tigecycline. The GFP-expressing population (i.e. the resistant population) nearly went undetected because it only represented approximately 10^?6 of the entire population. However, when the mimicked tigecycline-heteroresistant strain was treated with tigecycline, most subpopulations expressing GFP were detected. The surviving A. baumannii population, upon exposure to tigecycline, exhibited a high minimum inhibitory concentration for tigecycline, equivalent to that of tigecycline-resistant isolates that were used to mimic heteroresistance. These results indicate that the development of resistance in tigecycline-heteroresistant A. baumannii strains, resulting in decreased antibiotic efficacy, may depend on the selection of a pre-existing resistant subpopulation.     

New developments in tetracycline antibiotics: glycylcyclines and tetracycline efflux pump inhibitors.

The tetracyclines, discovered in the 1940s, are a well-established class of antibiotics that still have a role in treating microbial infections in man. However, the widespread emergence of bacterial resistance due to efflux and ribosomal protection mechanisms has severely limited their effectiveness. A new generation of tetracyclines, the glycylcyclines, has been developed to overcome resistance to earlier tetracyclines. One of the new glycylcyclines, 9-t-butylglyclamido-minocycline (GAR-936, tigecycline) is currently undergoing clinical trials. This review considers the current status of glycylcyclines and the possibility that resistance to these agents might arise in the future. Other approaches are also being taken to address the emergence of resistance to tetracyclines. Recently, a number of tetracycline efflux pump inhibitors have been discovered that might be used in combination with earlier tetracyclines to restore their activity against resistant organisms. However, the development of tetracycline efflux pump inhibitors is complicated by the occurrence of several efflux pump sub-families and by the presence of both efflux and ribosomal protection mechanisms in the same organism, especially in naturally occurring, Gram-positive clinical isolates.     

The glycylcyclines: a comparative review with the tetracyclines

The tetracycline class of antimicrobials exhibit a broad-spectrum of activity against numerous pathogens, including Gram-positive and Gram-negative bacteria, as well as atypical organisms. These compounds are bacteriostatic, and act by binding to the bacterial 30S ribosomal subunit and inhibiting protein synthesis. The tetracyclines have been used successfully for the treatment of a variety of infectious diseases including community-acquired respiratory tract infections and sexually transmitted diseases, as well in the management of acne. The use of tetracyclines for treating bacterial infections has been limited in recent years because of the emergence of resistant organisms with efflux and ribosomal protection mechanisms of resistance. Research to find tetracycline analogues that circumvented these resistance mechanisms has lead to the development of the glycylcyclines. The most developed glycylcycline is the 9-tert-butyl-glycylamido derivative of minocycline, otherwise known as tigecycline (GAR-936). The glycylcyclines exhibit antibacterial activities typical of earlier tetracyclines, but with more potent activity against tetracycline-resistant organisms with efflux and ribosomal protection mechanisms of resistance. The glycylcyclines are active against other resistant pathogens including methicillin-resistant staphylococci, penicillin-resistant Streptococcus pneumoniae, and vancomycin-resistant enterococci. Tigecycline is only available in an injectable formulation for clinical use unlike currently marketed tetracyclines that are available in oral dosage forms. Tigecycline has a significantly larger volume of distribution (> 10 L/kg) than the other tetracyclines (range of 0.14 to 1.6 L/kg). Protein binding is approximately 68%. Presently no human data are available describing the tissue penetration of tigecycline, although studies in rats using radiolabelled tigecycline demonstrated good penetration into tissues. Tigecycline has a half-life of 36 hours in humans, less than 15% of tigecycline is excreted unchanged in the urine. On the basis of available data, it does not appear that the pharmacokinetics of tigecycline are markedly influenced by patient gender or age. The pharmacodynamic parameter that best correlates with bacteriological eradication is time above minimum inhibitory concentration. Several animal studies have been published describing the efficacy of tigecycline. Human phase 1 and 2 clinical trials have been completed for tigecycline. Phase 2 studies have been conducted in patients with complicated skin and skin structure infections, and in patients with complicated intra-abdominal infections have been published as abstracts. Both studies concluded that tigecycline was efficacious and well tolerated. Few human data are available regarding the adverse effects or drug interactions resulting from tigecycline therapy; however, preliminary data report that tigecycline can be safely used, is well tolerated and that the adverse effects experienced were typical of the tetracyclines (i.e. nausea, vomiting and headache). Tigecycline appears to be a promising new antibacterial based on in vitro and pharmacokinetic/pharmacodynamic activity; however more clinical data are needed to fully evaluate its potential.     

细菌多重耐药外排泵抑制剂研究进展

细菌耐药性，尤其是多重耐药性（multi-drug resistance，MDR）已经成为非常严重的医疗问题，而多种类型细菌外排泵（efflux pumps）的存在是细菌多重耐药的重要机制，因此寻找有应用前景的外排泵抑制剂（efflux pump inhibitors，EPI）是十分必要且迫切的。目前已经发现外排泵抑制剂的作用机制分为：（1）干扰外排泵组装；（2）阻断外排泵能量来源；（3）阻碍底物通过外排通道；（4）机制未知。本文按照作用机制对已经发现的细菌多重耐药外排泵抑制剂的特点进行分述。     

51株鲍曼不动杆菌耐药表型及外排蛋白基因表达研究

目的:探讨鲍曼不动杆菌耐药表型以及adeB外排泵基因的表达情况。方法:收集2004年2月～2005年2月北京协和医院51株非重复鲍曼不动杆菌,应用聚合酶链反应法测定鲍曼不动杆菌主动外排系统adeB结构基因及序列分析。结果:受试菌株对常用广谱抗生素均不敏感;多重耐药鲍曼不动杆菌携带adeB主动外排泵基因。结论:本研究中鲍曼不动杆菌多重耐药性与产生β-内酰胺酶无关,另有其它耐药机制存在,主动外排作用可能是鲍曼不动杆菌多重耐药的重要机制之一。     

多重耐药淋病流行株孔蛋白和泵蛋白的表达

为探讨外排系统、外膜通透性与淋病流行株多重耐药性的关系。应用KB法和琼脂稀释法从湛江地区分离出62株淋球菌多重耐药株；利用SDS—PAGE法测定淋球菌外膜孔蛋白的表达；采用直接荧光法测定能量抑制剂NaNa加入前后淋球菌对抗生素的摄入和积累情况，比较耐药菌与敏感菌内膜泵蛋白表达的差异。结果显示，5株多重耐药菌均有外膜孔蛋白表达的缺失或下降，同时伴有外排泵蛋白的表达。提示外排系统、外膜通透性与淋病流行株的多重耐药性密切相关。     

Role of efflux mechanisms on fluoroquinolone resistance in Streptococcus pneumoniae and Pseudomonas aeruginosa

Prokaryotic efflux mechanisms can effectively increase the intrinsic resistance of bacteria by actively transporting antibiotics out of cells, thus reducing the effective concentration of these agents. The fluoroquinolones, similar to most other antimicrobial classes, are susceptible to efflux mechanisms, particularly in Gram-negative organisms, such as Pseudomonas aeruginosa. Resistant P. aeruginosa clones isolated after fluoroquinolone therapy frequently over express at least one of the multiple efflux pump mechanisms found in this organism. Gram-positive bacteria, such as Streptococcus pneumoniae, also possess efflux mechanisms, though their effect on fluoroquinolone resistance seems to be more limited and selective. In the future, efflux pump inhibitors may offer effective adjunctive therapy to antibiotics for the treatment of difficult infections by efflux mutants. In the meantime, appropriate antibiotic selection and optimal dosing strategies should aim to eradicate the causative pathogen before a resistant efflux mutant can emerge.     

微生物药物外排泵及其抑制剂研究

细菌自身的不断进化及抗生素的不合理使用导致了耐药性细菌的出现和蔓延，微生物的主动外排是导致细菌产生多重耐药的重要原因。微生物外排泵的研究是目前的热点之一，也被认为是开发新抗生素的理想靶标。本文从基因组和比较基因组水平对外排泵的类型、作用机制、表达调控及研究方法等方面概述，并结合正在开展的分枝杆菌的药物外排泵进行了比较基因组分析。这些工作有利于开发新的抗生素或抗生素增效剂。