首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到19条相似文献，搜索用时 15 毫秒
1.
通过微量稀释法测定28株猪源链球菌对环丙沙星的MIC值,研究东北地区猪源链球菌对环丙沙星耐药性与parC、gyrA基因突变的相关性.通过PCR方法扩增parC和gyrA基因喹诺酮耐药决定区(QRDR)并测序分析;18株耐药菌在parC基因80位的突变(AGC→ATT)导致氨基酸Ser→Ile突变,11株高度耐药菌在gyrA基因81位的突变(CAG→)CAT、CTT或CTA)导致氨基酸Ser→Ile、Phe或Tyr的突变.当菌株对环丙沙星的MIC值≤1μ/mL时,parC和gyrA基因的QRDR区均未有突变;而当MIC ≥2μg/mL时,ParC的氨基酸发生了Ser80→Ile的突变,同时发生GyrA氨基酸Ser81突变的菌株,耐药水平很高.研究表明,环丙沙星低水平类耐药是由于拓扑异构酶Ⅳ改变引起,而高水平耐药是由拓扑异构酶Ⅳ、DNA旋转酶共同改变引起的.实验结果证明,在一定条件下,耐药性的高低与突变位点的多少成正比.  相似文献   

2.
旨在了解猪链球菌对氟喹诺酮类药物耐药性与parC、gyrA基因突变的相关性,通过微量稀释法测定34株猪链球菌对4种氟喹诺酮类药物的MIC值,采用PCR方法扩增并测序分析了临床分离的猪链球菌对氟唪诺酮类约物10株耐药株和9株敏感株的parC和gyrA基因喹诺酮耐药决定区(QRDRs).在氟喹诺酮类药物耐药菌株parC基因QRDRs发生Ser79→Phe、Arg 87→Leu的氨基酸突变,在4株高度耐药菌株gyrA基因QRDRs发生Arg66→Ser,Ser81→Arg氨基酸突变;当菌株对氟喹诺酮类药物敏感时,parC和gyrA基因的QRDR区均未有突变;而当MIC≥32 μg·L-1 时,parC的氨基酸发生了 Ser79→Phe的突变,同时发生gyrA氨基酸Arg66→Ser,Set81→Arg突变.结果表明,猪链球菌对氟喹诺酮类药物低水平类耐药是由parC单一位点突变引起,而高水平耐药是由parC和gyrA双位点突变引起.  相似文献   

3.
测定了我国痢疾流行病原志贺菌福氏2a 301株与喹喏酮类药物耐药性相关的gyrA(DNA旋转酶A亚单位）和parC（拓扑异构酶IVA亚单位）基因，并将gyrA和parC基因QRDR（喹喏酮类药物耐药性决定区）核苷酸序列与几种动物和人的病原菌进行了同源性和遗传进化比较分析，结果显示，志贺菌福氏2a gyrA和parC基因QRDR序旬分别与宋内氏志贺菌菌、大肠杆菌O157、大肠杆菌K12、阴沟肠杆菌、坂口肠道杆菌、鼠伤寒沙门氏菌、副伤寒沙门氏菌、坂口肠道杆菌、鼠伤寒沙门氏菌、副作寒沙门氏菌，肺炎克氏杆菌、产道氏杆菌、副伤寒沙门氏菌、肺炎克氏杆菌、产道克氏杆菌、空肠弯曲杆菌、沸氏柠檬酸杆菌具有显著同源性（均大于88％），表明gyrA和parC是这些细菌中的看家基因，推测在各种细菌中具有类似的起源，因此，对在不同细菌之间进行喹喏酮类药物耐药性的研究非常有利。QRDR的遗传进化分析表明，同属或相近属细菌gyrA或parC QRDR的遗传距离明显接近，其中与大肠杆菌属的距离最近，认为可列到同一个性中，结果有力支持了近年提出的大肠杆菌与志贺菌属于同族细菌的理论，研究对理解喹喏酮类药物耐药性的分子机理及其与细菌遗传进货之间的关系具有重要意义。  相似文献   

4.
通过对采集于山东省肉鸡屠宰场的202株空肠弯曲菌进行喹诺酮类耐药分子机制的研究,包括7种可以移动耐药基因筛查,喹诺酮耐药决定区(QRDR)突变检测和parC的筛查,确定了我国山东省鸡源空肠弯曲菌对喹诺酮类药物的耐药表型主要为gyrA中QRDR C-257-T突变所造成.并发现在空弯中存在于gyrA和gyrB基因上的部分沉默突变有着地域流行性特点.这些观察结果为解释我国食品动物源空肠弯曲菌耐药性现状,防控耐药空肠弯曲菌传播和流行提供基础数据.  相似文献   

5.
15株动物源性耐氟喹诺酮类药物大肠杆菌进行PCR检测、测序、WDNASIS软件分析gyrA基因中的氟喹诺酮耐药决定区(QRDR)、AcrA以及编码与质粒介导的氟喹诺酮类药物耐药机制相关的qnrA、qnrB、qnrS、qepA和aac(6′)-Ib-cr基因。结果表明,15株耐药菌中,QRDR基因在其编码第72、75、83位或第87位氨基酸均发生突变;AcrA基因未检测到氨基酸的突变;qnrS、qepA和aac(6′)-Ib-cr耐药基因阳性菌各检测到1株,序列分析表明不存在氨基酸突变。QRDR基因编码的氨基酸4个位点发生突变,其中Ser83→Leu和Asp87→Asn 2个基因的突变均与文献报道的突变相同,双突变的7个菌株均表现为高度耐氟喹诺酮类抗生素,表明gyrA基因为大肠杆菌耐氟喹诺酮类抗生素的一个重要机制。高度耐氟喹诺酮类抗生素的菌株中有2株没有检测到氨基酸突变的存在,但是aac-(6′)-Ib-cr基因和qnrS检测为阳性,表明质粒介导的喹诺酮类耐药也可单独导致菌株的耐药。存有一个菌株gyrA基因编码的氨基酸发生突变Ser83→Leu,AcrA基因和qnrA、qnrB、qnrS、qepA和aac(6′...  相似文献   

6.
对河南省猪产业链中分离的28株耐头孢菌素沙门菌进行血清学分型、药敏试验和超广谱β-内酰胺酶(ESBLs)筛查，并进一步采用PCR扩增和DNA测序检测β-内酰胺基因、喹诺酮类耐药基因以及喹诺酮类耐药决定区(QRDR)氨基酸突变。结果显示，河南省猪产业链中耐头孢菌素沙门菌的流行率为0.89%(28/3 137),其中肝脏样品流行率最高(4.98%,16/321);28株检测菌，共分为7种血清型，主要血清型为印第安纳(46.43%,n=13)和单相鼠伤寒变种(25%,n=7)。所有菌株除了黏杆菌素，对其他11种药物耐药率均高于60%,多重耐药率为100%;至少携带1种β-内酰胺酶基因，携带率最高的基因是blaCTX-M(89.29%,n=25),共携带有6种组合的β-内酰胺酶基因谱；共检测到4种喹诺酮类耐药基因(aac(6)-Ib-cr、oqxAB、qnrS和qnrC),gyrB和parE均无氨基酸突变，其中15株菌同时发生gyrA(Ser83Phe与Asp87Asn/Gly)突变和parC(Thr57Ser与Ser80Ile/Arg)突变，无论是否存在喹诺酮耐药基因，对环丙沙星均呈高水平的...  相似文献   

7.
采用二倍稀释法测定临床分离的4株鸡毒支原体对常用抗菌药物的敏感性,PCR方法和基因测序法对鸡毒支原体DNA回旋酶编码基因gyrA、gyrB及拓扑异构酶Ⅳ编码基因parC和parE耐药决定区进行分析。敏感性测定结果表明,4株分离鸡毒支原体对泰乐菌素、泰妙林、沃尼妙林和替米考星有很高的敏感性,对四环素和红霉素中度敏感,对林可霉素、氟苯尼考和氟喹诺酮类药物呈现不同程度的耐药性。4株耐氟喹诺酮类药物鸡毒支原体均在GyrA和ParC的喹诺酮类耐药决定区(QRDR)发生氨基酸的改变,GyrA的氨基酸取代模式有两种,分别为Ser81→Gly和Ser83→Ile,ParC仅在80位发生氨基酸取代(Ser80→Leu),GyrB和ParE均未发生氨基酸改变。  相似文献   

8.
测定了痢疾杆菌福氏2a301株与喹诺酮类药物耐药性相关的gyrA基因和ParC基因的序列，并对其环丙沙星耐药诱变株的gyrA和ParC基因喹诺酮类药物耐药性决定区(QRDR)序列进行了测定分析。结果表明，痢疾杆菌福氏2a301株gyrA和ParC基因分别为2625bp和2256bp，环丙沙星诱导的耐药菌gyrA基因QRDR(245bp)发生氨基陵残基69—Ala→Val和87—Tyr→AsP改变，ParC基因QRDR(237b)发生氨基酸残基79—Ala→Asp、84—Ala→Glu和85—Pro→Ala改变。这一研究结果对认识痢疾杆菌喹诺酮类药物耐药性的分子机理具有重要意义。  相似文献   

9.
用微量稀释法测定盐酸环丙沙星等5种氟喹诺酮类抗菌药物对20株耐氟喹诺酮类药物的动物源致病性大肠杆菌的最低抑菌浓度(MIC),PCR扩增gyrA基因的喹诺酮耐药决定区(quinolone resistance determining regions,QRDR),扩增的片断长度为496 bp,PCR产物直接测序,用DNAStar软件分析氨基酸序列。结果显示,盐酸环丙沙星、恩诺沙星、氧氟沙星、甲磺酸培氟沙星和烟酸诺氟沙星的MIC范围分别为64～>512μg/mL、16～256μg/mL、16～128μg/mL、64～>512μg/mL和64～>512μg/mL。gyrA基因的突变位点均位于83和87位氨基酸位点,主要的变异方式为Ser83→Leu(15/20),其次是Asp87→Asn(13/20),其他的为Asp87→Tyr(6/20),Ser83→Trp(4/20),Ser83→Ala(1/20)和Asp87→Gly(1/20)。说明试验用菌株对氟喹诺酮类药物均表现为多重耐药,其gyrA基因QRDR的突变表现为多种形式。  相似文献   

10.
鸭疫里默氏菌的gyrA基因的检测与变异位点的分析   总被引：1，自引：0，他引：1  
近年来，随着喹诺酮类药物的广泛应用，尤其是一些养殖场的盲目滥用和超量服用，导致耐药菌株不断出现。关于耐药的大肠埃希氏菌、金黄色葡萄球菌、粪肠球菌、铜绿假单胞菌等细菌在其螺旋酶gyrA基因的喹诺酮类药物决定区（QRDR）的突变热点已有很多报道，这些菌株的突变热点相对于大肠杆菌来说，发生在第83位和87位的氨基酸上。到目前为止，鸭疫里默氏菌螺旋酶gyrA基因还是未知的，其耐药基因的突变更没有报道。本试验测出了鸭疫里默氏菌gyrA的部分基因，找到了对喹诺酮类抗生素耐药菌株的基因突变热点和突变规律。为以后研究鸭疫里默氏菌对喹诺酮类抗生素耐药的分子机制提供了基础。  相似文献   

11.
沙门氏菌耐药株gyrA基因和parC基因突变特征分析   总被引：3，自引：0，他引：3  
提取沙门氏菌染色体DNA，设计引物扩增gyrA基因和parC基因片段，克隆测序寻找耐药菌株的突变位点，通过系统的比较，分析氟喹诺酮类药物（以环丙沙星为代表）对各沙门氏菌MIC和耐药突变位点之间的关系。通过对耐药突变位点的研究，可以为下一步研究耐药性监测的快速方法提供理论基础。  相似文献   

12.
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.  相似文献   

13.
The prevalence of qnr genes was investigated in veterinary clinical isolates of Escherichia coli in Guangdong province, China, and the aac (6')-Ib gene and the mutations in QRDRs of gyrase and topoisomerase IV were examined in qnr-positive strains. A total of 232 E. coli strains isolated from pig and poultry were screened for the presence of the qnrA, qnrB and qnrS genes by PCR and sequencing. The aac (6')-Ib gene was detected in qnr-bearing strains by PCR and sequencing. For all strains carrying qnr, MICs for six quinolones were determined. Mutations within the gyrase and topoisomerase were analyzed by PCR and sequencing for all the QRDRs of gyrA, gyrB, parC and parE. Among 232 E. coli isolates, 14 (6%) isolates were positive for the qnr gene, including one for qnrB, 13 for qnrS, but no qnrA was identified in this population. Detection of the aac (6')-Ib gene showed that one qnrS-positive isolate from pig and one qnrB-positive isolate from duck carried aac (6')-Ib gene, and both were the cr variant allele of aac (6')-Ib. All of the 14 isolates had MICs of ciprofloxacin more than 0.25 mg/L. Mutations in the QRDR of gyrA mutations were observed in 5 (35.7%) of the 14 strains. Three fluoroquinolone-resisting strains showed one mutation S83L of gyrA, while one S83I. One high-level resistance strains harboured gyrA S83L and A87N of gyrA. A singe mutation in site 58 of parC was detected in 3 (21.4%) strains. None mutations were found in QRDRs of gyrB and parE. The emergence of qnr genes in veterinary clinical E. coli isolates is described for the first time. This is also the first report of aac (6')-Ib-cr gene in E. coli isolates from food-producing animals.  相似文献   

14.
Thirty-seven fluoroquinolone-resistant Escherichia coli strains from ruminants (according to Clinical and Laboratory Standards Institute guidelines) were screened by molecular methods for mutations in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes and for the presence of the qnrA gene. One of the strains studied was an enterohemorrhagic E. coli (EHEC) strain potentially pathogenic for humans. Three E. coli strains resistant to enrofloxacin (minimal inhibitory concentration [MIC] = 2 microg/ml) but not to ciprofloxacin (MIC = 1 microg/ml) presented single mutations in the gyrA and parC genes, while 34 strains resistant to both fluoroquinolones presented double and single mutations in gyrA and parC, respectively (31 strains), or double mutations in gyrA and parC (3 strains). The EHEC strain presented a double amino acid substitution in the GyrA protein (Ser-83-->Leu and Asp-87-->Gly) and a double amino acid substitution in the ParC protein (Gly-78-->Cys and Ser-80-->Arg), one of which has not been previously described. The present study shows that most of the mutations in the QRDR of the gyrA and parC genes of fluoroquinolone-resistant E. coli strains from ruminants are the same as those seen in E. coli strains from other animal species and humans and that there are no differences in mutation patterns in the QRDR of E. coli strains from healthy ruminants and those with diarrhea. No strains carried qnrA, which indicates that this gene does not play an important role in the selection of fluoroquinolone-resistant E. coli strains from ruminants.  相似文献   

15.
Quinolone-resistant (QR) mutants of Mycoplasma bovirhinis strain PG43 (type strain) were generated by stepwise selection in increasing concentrations of enrofloxacin (ENR). An alteration was found in the quinolone resistance-determining region (QRDR) of the parC gene coding for the ParC subunit of topoisomerase IV from these mutants, but not in the gyrA, gyrB, and parE gene coding for the GyrA and GyrB subunits of DNA gyrase and the ParE subunit of topoisomerase IV. Similarly, such an alteration in QRDR of parC was found in the field isolates of M. bovirhinis, which possessed various levels of QR. The substitution of leucine (Leu) by serine (Ser) at position 80 of QRDR of ParC was observed in both QR-mutants and QR-isolates. This is the first report of QR based on a point mutation of the parC gene in M. bovirhinis.  相似文献   

16.
Quinolone-resistance determining region (QRDR) of Gyrase A gene was sequenced in 54 Salmonella strains of pig origin that have different quinolone-resistance patterns. Those strains accounted for 12 different serotypes. Mutations at Ser83 or Asp87 were predominant in the studied isolates. However, for serotypes Anatum and Virchow, resistance to quinolones seemed to be linked to specific mutations, namely, Ser83-->Tyr and Ser83-->Phe, respectively. Other mutations found in different positions did not seem to have clinical significance except for changes at Asp82.  相似文献   

17.
OBJECTIVE: To investigate the development of enrofloxacin resistance among Escherichia coli isolates obtained from chickens by determining mutant-prevention concentrations (MPCs) and sequence the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes in selected isolates. SAMPLE POPULATION: 15 chicken-derived E coli isolates. PROCEDURES: For all isolates, MPC and minimal inhibition concentration (MIC) of enrofloxacin were determined. The MPCs and maximum serum drug concentrations attained with enrofloxacin doses recommended for treatment of E coli infections in chickens were compared. Mutation frequencies and QRDR sequence changes in gyrA and parC were also determined. RESULTS: In 2 of 15 E coli strains, MPCs were low (0.016 and 0.062 microg/mL), MPC:MIC ratios were 2 and 4, and the GyrA and ParC proteins had no mutations. In 9 susceptible isolates with a GyrA point mutation, MPCs ranged from 2 to 16 microg/mL. For isolates with double mutations in GyrA and a single mutation in ParC, MPCs were > 32 microg/mL (several fold greater than the maximal plasma concentration of enrofloxacin in chickens); mutation frequencies were also much lower, compared with frequencies for single-mutation isolates. CONCLUSIONS AND CLINICAL RELEVANCE: For E coli infections of chickens, MPC appears to be useful for determining enrofloxacin-dosing strategies. The high MPC:MIC ratio may result in enrofloxacin-treatment failure in chickens infected with some wild-type gyrA E coli isolates despite the isolates' enrofloxacin susceptibility (MICs 0.125 to 1 microg/mL). For infections involving isolates with high MPCs, especially those containing mutations in gyrA and parC genes, treatment with combinations of antimicrobials should be adopted.  相似文献   

18.
Niwa H  Hobo S  Anzai T 《Veterinary microbiology》2006,115(1-3):264-268
In this study, the quinolone resistance-determining region (QRDR) in gyrA and gyrB of in vitro fluoroquinolone-resistant Rhodococcus equi mutants was sequenced. These mutants were selected from four R. equi strains on blood agar plates containing ciprofloxacin or enrofloxacin. Each mutant became 8- to 64 or greater-fold resistant to fluoroquinolones compared with their parent strains. From the results of sequence analysis of QRDR in gyrA and gyrB, a nucleotide mutation of codon GAC for GGC in gyrA was detected in all mutants, but no mutation was observed in gyrB. This mutation leads to amino acid substitution of Asp for Gly in putative GyrA in R. equi. The position of this substitution corresponds to position 87 of GyrA in Escherichia coli. Our results suggest that the mutation of QRDR in gyrA, which was observed in in vitro fluoroquinolone-resistant R. equi mutants in this study, is closely associated with fluoroquinolone resistance.  相似文献   

19.
The aim of this study was to determine antimicrobial resistance of Aeromonas hydrophila isolated from farmed Nile Tilapia. A total of 50 A. hydrophila isolates from clinical cases were screened for the presence of class 1, 2 and 3 integrons and all the strains resistant to enrofloxacin and/or ciprofloxacin (n=19) examined for mutation in the quinolone resistance-determining regions (QRDRs) of gyrA and parC. The intI1 gene was detected in 23 A. hydrophila strains (46%) but no intl2 and intl3 were detected. Among these, 14 isolates (60.8%) carried gene cassettes inserted in variable regions i.e., partial aadA2, aadA2, dfrA1-orfC and dfrA12-aadA2, of which the most common gene cassette array was dfrA12-aadA2 (26.09%). Conjugal transfer of class 1 integrons with resistance gene array was detected. All the A. hydrophila strains resistant to enrofloxacin and/or ciprofloxacin possessed mutations in the QRDRs of gyrA and parC. Only a Ser-83-Ile substitution was identified in GyrA and only a Ser-80-Ile amino change was found in ParC. The data confirms that A. hydrophila from farm-raised Nile Telapia serve as a reservoir for antimicrobial resistance determinants.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号