质粒介导的喹诺酮类药物耐药机制研究进展

<正>肠杆菌科细菌对喹诺酮类药物耐药性日益加重,以往喹诺酮类的耐药研究多集中在染色体介导的靶位改变、膜通透性降低、外排泵亢进机制,质粒介导的喹诺酮类耐药鲜见报道。近年来出现一种质粒介导的喹诺酮耐药(plasmid-mediated-quinolone-resistance,PMQR)因子,是一种新的喹诺酮耐药机制。到目前为止发现3大类(qnr,aac(6′)-Ib-cr和qep A或oqx AB)由质粒介导的喹诺酮耐药类型。这些由质粒介导的耐药基因可以在菌间进行水平传     

贵阳市大肠杆菌质粒介导的喹诺酮耐药基因检出率与耐药相关性研究

<正>1998年L.MARTINEZ-MARTINEZ等[1]报道了质粒p MG252可使细菌对氟喹诺酮药的耐药水平提高,并将该喹诺酮类耐药基因命名为qnr基因。近年的研究结果表明,质粒介导的喹诺酮类药物耐药性是喹诺酮类药物耐药机制的重要组成部分,它主要包括:qnr机制,乙酰基转移酶aac(6')-Ib-cr修饰喹诺酮类药物的耐药机制以及qep A介导的主动外排     

喹/诺/酮/类/抗/菌/药/耐/药/新/机/制

近年来喹诺酮类的耐药性问题备受关注。细菌对喹诺酮类的耐药机制过去普遍认为主要起因于染色体基因突变(靶位改变、主动外排和膜孔蛋白缺失),而不存在水平传播的可转移基因。近年来开始出现一些新的喹诺酮耐药机制,包括qnr、mfpA和氨基糖苷乙酰转移酶的变异基因(aac(6’)-Ib-c     

沙门氏菌和大肠埃希氏菌耐药基因qnrS研究进展

qnrS是质粒介导的喹诺酮类药物的耐药基因,通过保护DNA回旋酶活性从而降低宿主菌对喹诺酮类药物的敏感性。这种保护作用依赖于qnrS基因的表达水平,同时,qnrS的表达主要受喹诺酮类药物浓度的影响,且σ-D调控因子(regulator of sigma D,Rsd)也参与该基因的表达调控。qnrS基因在沙门氏菌中高度流行,并且是大肠埃希氏菌中质粒介导的喹诺酮类耐药基因的优势基因。qnrS可以在细菌间进行传播,或与其他耐药基因共存于同一质粒上发生共转移,从而导致多重耐药的发生。论文对qnrS基因的发现、表达及其调控机制、在沙门氏菌和大肠埃希氏菌中的流行及传播的研究进展进行综述,以期为控制qnrS基因介导的耐药性提供参考。     

质粒介导的氟喹诺酮类抗生素耐药机制研究进展

近年来,质粒介导的耐药已经成为细菌对氟喹诺酮类抗生素耐药(PMQR)的主要机制之一。质粒携带的耐药基因种类不断增多,且其耐药基因可随质粒在不同种属细菌间相互传递,进而引起细菌耐药性的广泛传播,得到了国内外相关工作者的高度关注。本文将就近年来有关质粒携带氟喹诺酮类药物耐药基因的研究进展做以综述,为其耐药机制进一步研究奠定理论基础。     

不同地区鸡源大肠杆菌质粒介导的喹诺酮类药物耐药基因调查

喹诺酮类药物是兽医临床治疗动物细菌性疾病一类常用抗菌药物,此类药物的广泛应用,使动物源大肠杆菌对其耐药性也随之逐渐上升[1].细菌对喹诺酮类药物的耐药机制主要是染色体介导的靶位改变、膜通透性改变和主动外排.近年来,质粒介导的喹诺酮类药物耐药(plasmid mediated quinolone resistance,PMQR)基因qnrA[2],qnrB[3]、qnrS[4]相继出现,aac(6’)-Ib-er和qepA这两种质粒介导的耐药基因也被证实[5-6].本试验通过微量肉汤稀释法,检测2009年鸡源大肠杆菌的耐药情况,选择耐喹诺酮类药物的菌株,采用PCR方法检测PMQR基因,以了解不同地区鸡源大肠杆菌中PMQR基因的流行情况.     

猪源氟喹诺酮耐药大肠杆菌通过接合水平传递耐药性的研究

为研究猪源大肠杆菌中可移动质粒在氟喹诺酮类药物耐药性水平传播机制中的作用,作者对氟喹诺酮耐药且PMQR基因阳性的大肠杆菌进行接合试验,并对所得接合子采用微量肉汤稀释法测定其对8种常见药物的最小抑菌浓度(MIC),针对质粒介导的氟喹诺酮耐药基因(PMQR)设计特异性引物对接合子进行PCR扩增。研究结果显示,41株氟喹诺酮耐药且PMQR基因阳性的供体菌共接合成功16株细菌,接合成功率高达39%,接合子与受体菌J53相比,均呈现一定的耐药表型,与供体菌相比,87.5%的接合子存在耐药谱型的变化,并且存在丢失一种药物耐药性,产生另一种药物耐药性的现象,PCR结果显示,接合子与供体菌相比,基因型有所减少,接合子中qnrS基因接合成功率最高,12.5%的接合子发生oqxA、oqxB和qnrS的共转移。本研究表明不同的PMQR基因在可移动质粒介导耐药性水平传播的过程中接合成功率存在差异,不同的PMQR基因有可能位于不同的可移动质粒上,通过比较接合前后供体菌和受体菌耐药表型的变化,尤其是PMQR基因检出率的变化,可以初步确定,可移动性质粒在大肠杆菌耐药性水平传播的过程中起到了非常重要的作用。     

噬菌体在细菌耐药性传播中的作用及分子机制

细菌耐药性是威胁人类健康的全球问题,对于耐药性传播机制的研究受到广泛关注。目前已知的可以介导细菌耐药性/耐药基因水平转移的机制包括转化、接合转移和转导等,其中质粒等可转移元件在细菌耐药性传播过程中发挥的作用已经得到共识,而对于噬菌体介导的耐药性转导作用及机制关注较少。噬菌体是一种感染细菌的病毒,其在生态环境中广泛存在,其对细菌基因组的多样性和细菌的进化发挥了重要作用。本文综述了噬菌体的类型、前噬菌体分布、噬菌体与耐药基因的共存现象、噬菌体介导的耐药基因转移证据及其分子机制、噬菌体对肠道菌群的影响等方面,指出有必要重新认识噬菌体对于细菌耐药性发展的重要性,并对噬菌体/耐药性的未来研究方向进行了展望。     

质粒介导的大肠杆菌对喹诺酮类药物耐药性研究进展

由于临床不合理用药,喹诺酮耐药菌株逐年增加,而且多重耐药菌株也越来越多,这给临床用药和新药开发带来了较大的困难,尤其是在临床分离菌株中出现质粒介导的喹喏酮耐药(PMQR)机制,使喹喏酮耐药性在人类、动物病原菌之间迅速传播成为可能。文章对大肠杆菌PMQR机制进行综述,以便对耐药分子机制的了解和控制耐药菌株的传播。     

临床16S rRNA甲基化酶的研究新进展

16SrRNA甲基化酶是近年来出现于临床的一种新耐药决定因子,介导细菌对多种氨基糖苷类高水平耐药,最初发现于肠杆菌科中,目前在革兰阴性菌中已发现至少由12种等位基因编码的10种16SrRNA甲基化酶。由于大多编码16SrRNA甲基化酶的基因常位于可动遗传因子如接合型质粒、整合子、转座子、插入序列共同区上,易引起耐药性和耐药基因的传播,导致临床抗感染治疗的失败。本文综述了临床16SrRNA甲基化酶的新发现,其介导的耐药性、作用机制、临床流行特点、传播特点及分子遗传背景、来源及进化,为临床合理应用氨基糖苷类抗生素、开发16SrRNA甲基化酶抑制剂奠定基础。     

喹诺酮类药物耐药机制研究进展

喹诺酮类属于合成的广谱抗菌药,用于治疗与肠杆菌科相关的各种感染性疾病。近几十年来,喹诺酮类药物的广泛使用和过度使用导致了喹诺酮耐药菌株的出现。喹诺酮类药物耐药的产生是一个复杂的多因素过程,主要的耐药机制包括染色体介导的一个或多个靶点基因突变改变靶点酶的药物结合力;AcrAB-tolC多耐药外排泵的过表达和孔蛋白的改变导致药物摄取减少,外排增加;以及质粒介导的喹诺酮类耐药基因(qnr,aac(6′)-Ib-cr和crpP)、外排泵(如OqxAB和QepA)的存在。论文通过对喹诺酮类药物耐药机制进行综述,以期为探索抗耐药菌株的新药提供参考。     

Research Advances on Antibacterial Activity and Bacterial Resistance of Quinolones

Quinolones (QLs) are synthetic antimicrobials and widely used to treat clinical bacterial disease in the world. Quinolones trap DNA gyrase or topoisomerase Ⅳ to form reversible drug-enzyme-DNA complexes and prevent protein synthesis,resulting in bacteriostasis. Recently, the analysis of crystal structures of cleaved complexes and building of the model of noncatalytic magnesium ion present a reasonable explanation for the phenomenon of the effect of quinolones antibacterial activity. There are many researches for the mechanisms of resistance of quinolones, gene mutation, altered drug permeation and plasmid-mediated quinolone resistance are three main aspects. Here, the molecular basis for the antibacterial action and mechanisms of resistance of quinolones were fully discussed and updated, so as to provide a large number of information for optimization of quinolone antimicrobials based on structural transformation.     

喹诺酮类药物的抗菌活性与细菌耐药性研究进展

喹诺酮类药物（quinolones,QLs）是一类化学合成的抗菌药物,曾在世界范围内广泛应用于临床细菌病的治疗。其作用靶点为细菌DNA螺旋酶和拓扑异构酶,形成药-酶-DNA三元复合体,阻止蛋白质合成,从而达到抑菌效果。目前,通过对许多三元复合体的晶体结构解析,以及非催化镁离子模型的建立,进一步合理地解释了喹诺酮类药物活性受到影响的现象。临床常见致病菌对喹诺酮类药物产生耐药现象的机理研究较多,主要是基因突变、膜对药物的通透性改变及质粒介导的喹诺酮耐药性（PMQR）3个方面。文章主要对喹诺酮类药物的作用机制和细菌耐药机理进行综述,以期为后期喹诺酮类药物结构优化提供更多的信息支持。     

Quinolone resistance in Escherichia coli.

Escherichia coli is an important pathogen of animals and humans that causes great financial cost in food production by causing disease in food animals. The quinolones are a class of synthetic antimicrobial agents with excellent activity against Escherichia coli and other Gram-negative bacteria used in human and veterinary medicine. Different quinolones are used to treat various conditions in animals in different parts of the world. All members of this class of drug have the same mode of action: inhibition of topoisomerase enzymes, DNA Gyrase and Topoisomerase IV. Escherichia coli can become resistant to quinolones by altering the target enzymes, reducing permeability of the cell to inhibit their entry, or by actively pumping the drug out of the cell. All these resistance mechanisms can play a role in high-level fluoroquinolone resistance, however target site mutations appear to be most important. As all quinolones act in the same way resistance to one member of the class will also confer decreased susceptibility to all members of the family. Quinolone resistant Escherichia coli in animals have increased in numbers after quinolone introduction in a number of different case studies. The resistance mechanisms in these isolates are the same as those in resistant strains found in humans. Care needs to be taken to ensure that quinolones are used sparingly and appropriately as highly resistant strains of Escherichia coli can be selected and may pass into the food chain. As these drugs are of major therapeutic importance in human medicine, this is a public health concern. More information as to the numbers of quinolone resistant Escherichia coli and the relationship between resistance and quinolone use is needed to allow us to make better informed decisions about when and when not to use quinolones in the treatment of animals.     

Prevalence and characteristics of quinolone resistance in Escherichia coli in veal calves

Quinolone resistance is studied and reported increasingly in isolates from humans, food-producing animals and companion animals. Resistance can be caused by chromosomal mutations in topoisomerase genes, plasmid-mediated resistance genes, and active transport through efflux pumps. Cross sectional data on quinolone resistance mechanisms in non-pathogenic bacteria from healthy veal calves is limited. The purpose of this study was to determine the prevalence and characteristics of quinolone resistance mechanisms in Escherichia coli isolates from veal calves, after more than 20 years of quinolone usage in veal calves. MIC values were determined for all isolates collected as part of a national surveillance program on antimicrobial resistance in commensal bacteria in food-producing animals in The Netherlands. From the strains collected from veal calves in 2007 (n=175) all isolates with ciprofloxacin MIC ≥ 0.125 mg/L (n=25) were selected for this study, and screened for the presence of known quinolone resistance determinants. In this selection only chromosomal mutations in the topoisomerase type II and IV genes were detected. The number of mutations found per isolate correlated with an increasing ciprofloxacin MIC. No plasmid-mediated quinolone resistance genes were found. The contribution of efflux pumps varied from no contribution to a 16-fold increase in susceptibility. No correlation was found with the presence of resistance genes of other antimicrobial classes, even though all quinolone non-wild type isolates were resistant to 3 or more classes of antibiotics other than quinolones. Over twenty years of quinolone usage in veal calves in The Netherlands did not result in a widespread occurrence of plasmid-mediated quinolone resistance, limiting the transmission of quinolone resistance to clonal distribution.     

副猪嗜血杆菌对喹诺酮类药物流行病学临界值的建立

为了解副猪嗜血杆菌对喹诺酮类药物的耐药现状，制定副猪嗜血杆菌对喹诺酮类药物的流行病学临界值，本试验根据CLSI-VET中规定的方法，对ScienceDirect、PubMed、中国知网等数据库中副猪嗜血杆菌对喹诺酮药物的耐药数据进行收集，共收集到605株环丙沙星、74株氧氟沙星、322株左氧氟沙星、211株达氟沙星、276株萘啶酸、143株洛美沙星、638株恩诺沙星及262株马波沙星的最小抑菌浓度数据，进行数据修正后利用统计软件ECOFFinder进行整理拟合，得出MIC拟合直方分布图，确定了副猪嗜血杆菌对8种喹诺酮类药物的流行病学临界值和耐药率。8种药物中可用于兽医临床使用的药物为达氟沙星、恩诺沙星、马波沙星、环丙沙星；萘啶酸作为第1代喹诺酮抗菌药，已基本退出市场；另外3种药物不可用于兽医临床。通过调查研究得出副猪嗜血杆菌对氧氟沙星、萘啶酸、洛美沙星、左氧氟沙星、环丙沙星、达氟沙星、马波沙星、恩诺沙星药物的流行病学临界值分别为8、4、4、0.25、0.25、0.0625、0.0625和0.03125 μg/mL，说明目前野生型副猪嗜血杆菌对环丙沙星、达氟沙星、马波沙星和恩诺沙星这4种兽医临床可用药敏感性较高，临床推荐使用。文章得出的数据在国际交流频繁的时代普遍适用，在国内外缺乏相应药效学折点和临床折点时可作为敏感和耐药的判定标准，并为进一步制定临床折点，指导临床用药、延长喹诺酮药物的临床使用寿命奠定了基础。     

PREVALENCE AND CHARACTERIZATION OF QUINOLONE RESISTANCE GENES IN PROTEUS SPECIES ISOLATED FROM PET TURTLES

Proteus spp. are widely recognized as opportunistic pathogens causing urinary tract and septic infections in humans and animals. The aim of this study was to investigate the prevalence of plasmid-mediated quinolone resistance genes and mutations in the quinolone resistance determining region in association with the detection of quinolone susceptibility of 24 strains of pet turtle-borne Proteus spp. Susceptibility of 4 antimicrobials including nalidixic acid, ciprofloxacin, ofloxacin, and levofloxacin was examined by disk diffusion and minimum inhibitory concentration test. Six isolates were resistant to nalidixic acid showing either intermediate resistance or resistance to other quinolones. All nalidixic acid, resistant isolates harbored mutations in gyrB (N440T/A401G/Q411S). Two of the isolates had both gyrA (S83I) and parC (S80I) mutations. Twenty-one isolates were positive for the presence of plasmid-mediated quinolone resistance genes; the qnrD gene had the highest prevalence with 19 (79.2%), while qnrS, qnrA, qnrB, and aac(6′), Ib-cr genes were present in 9 (37.5%), 2 (8.3%), 1 (4.2%), and 11 (45.8%) isolates, respectively. These results suggest that pet turtle-associated Proteus spp. should be considered a potential source of antimicrobial resistance determinants.     

65株不同圈养野生动物源性肠杆科菌的药敏分析

采用K-B法药敏试验,分析圈养野生动物肠杆科菌对青霉素类、头孢类、氨基糖甙类、喹诺酮类、磺胺类的10种临床常用抗生素的药敏情况。结果显示：最敏感的是头孢稀类的三代头孢,头孢哌酮和头孢噻肟,其敏感率均为83.1%;较敏感的为喹诺酮类和氨基糖甙类药物,敏感率大于或等于60%;敏感性较差的是一代头孢中的头孢拉定、磺胺类药中的复方新诺明、青霉素类的氨苄青霉素,其敏感性分别为58.5%、43.1%和21.5%,被研究结果为兽医临床用药提供了依据。     

Molecular basis of quinolone resistance in Escherichia coli from wild birds

Nine quinolone resistant (minimal inhibitory concentration [MIC] was > 32 microg/mL for nalidixic acid, > 1 microg/mL for ciprofloxacin) isolates of Escherichia coli have been found in wild birds with septicemia. All of the isolates were aerobactin positive. The mechanisms of resistance were characterised by sequencing the quinolone resistance-determining region (QRDR) of the gyrA, gyrB, parC, and parE genes. Sequence analysis of the gyrA gene in all isolates identified only 1 nucleotide substitution at codon Serine-83 for Leucine-83. Sequence analysis of the gyrB, parC, and parE QRDR genes revealed no mutations in any of the isolates. This study was conducted to determine the importance of these genes in the susceptibility of E. coli strains isolated from wild birds to quinolones.     

Mechanisms of quinolone resistance in Salmonella.

As in other Gram-negative bacteria, mechanisms of resistance to quinolones in Salmonella include target gene mutations, active efflux, and decreased outer membrane permeability. However, the exact contribution of these individual mechanisms to resistance, which may nevertheless interplay to reach high-level resistance, has not yet clearly been defined as in other bacteria such as Escherichia coli. This paper reviews the current state of knowledge of quinolone resistance mechanisms in Salmonella by comparison with that of E. coli and future directions of research with particular attention to the recent development of efflux pump inhibitors as possible means of avoiding the emergence and spread of fluoroquinolone resistance.