212～216年广东省中山社区鼠伤寒沙门菌同源性分析及对喹诺酮类药物耐药机制研究

目的 研究广东省中山社区鼠伤寒沙门菌(STM)的同源性及对喹诺酮类药物的耐药机制。方法 收集中山大学附属中山医院2012年3月～2016年12月临床分离鼠伤寒沙门菌78株(排除同一病人重复送检菌株)。通过琼脂稀释法检测鼠伤寒沙门菌对喹诺酮类药物的敏感度; 脉冲电场凝胶电泳(PFGE)方法分析耐药菌株的同源性; 使用PCR和DNA测序法分析gyrA,gyrB,parC和parE基因喹诺酮耐药决定区(QRDRs)的突变; PCR检测质粒介导喹诺酮类药物耐药基因qnr(qnrA,qnrB,qnrS,qnrD)和aac(6')-Ib-cr。结果 33株鼠伤寒沙门菌对环丙沙星产生耐药。33株鼠伤寒沙门菌共产生33种不同的PFGE图谱,相似度小于90%。29株耐药株gyrA位点发生单突变导致在第83或87位存在唯一氨基酸替代,其中第83位突变率占93.1%(27/29)。4株喹诺酮高耐药菌株的gyrA同时存在83和87号位双突变导致两个氨基酸发生替代,其中2株菌额外出现parC基因单碱基突变导致第80号位出现氨基酸替代。所有菌株中均未检测到qnr基因,但有15株鼠伤寒沙门菌检出aac-(6')-Ib-cr基因。结论 中山社区鼠伤寒沙门菌对喹诺酮类药物耐药性较高,主要机制是gyrA基因的单突变和携带aac-(6')-Ib-cr耐药基因。     

2008－2018年北京市人源鼠伤寒沙门菌的耐药与分子分型研究

  目的  分析2008—2018年北京市人源鼠伤寒沙门菌的耐药特征及分子分型特征。  方法  基于肠道病原监测平台收集的分离于2008—2018年的109株人源鼠伤寒沙门菌,采用生化检测试剂条和血清凝集试验进行菌株复核,采用微量肉汤法进行药敏试验,通过聚合酶链式反应方法检测β-内酰胺类、喹诺酮类和大环内酯类药物相关耐药基因,并通过脉冲场凝胶电泳（PFGE）进行分子分型分析。  结果  北京市鼠伤寒沙门菌对传统抗生素普遍耐药,多重耐药率达52.29%,对临床一线推荐药物环丙沙星、头孢类药物和阿奇霉素的耐药率分别为21.10%,17.43%和1.83%。 还发现了对头孢类药物和环丙沙星共同耐药以及对头孢类药物和阿奇霉素共同耐药的菌株。 耐药基因检测结果显示,耐头孢类药物菌株中,最常见的超广谱β-内酰胺酶基因是bla_TEM-1,其次是bla_CTX-M-14,同时也首次于鼠伤寒沙门菌中发现了bla_OXA-29基因的携带。 环丙沙星耐药主要与gyrA、parC和parE基因的点突变有关。 耐阿奇霉素菌株中未检测出相关耐药基因。PFGE分子分型结果显示,109株菌可分为67个带型,存在包含13株菌的优势带型。  结论  北京市人源鼠伤寒沙门菌耐药形势严峻,PFGE图谱呈多态性分布,相同PFGE带型菌株间具有更相似的耐药谱,需进一步加强肠道病原菌的耐药监测以有效控制耐药性的传播扩散。     

北京市21株鼠伤寒沙门菌多重耐药和分子分型研究

目的对北京市2009～2010年鼠伤寒沙门菌进行多重耐药及脉冲场凝胶电泳(PFGE)分型研究。方法对2009～2010年通过北京市肠道门诊监测系统分离到的21株鼠伤寒沙门菌进行生化鉴定、血清分型并应用WHO推荐的Kirby-Bauer法进行药敏试验,脉冲场凝胶电泳法进行PFGE分型。结果 21株鼠伤寒沙门菌中有13株多重耐药菌株(61.9%),其中2～3种抗生素耐药4株(30.77%),4～5种抗生素耐药2株(15.38%),6～7种抗生素耐药2株(15.38%),8～9种抗生素耐药5株(38.46%)。21株鼠伤寒沙门菌可分为17个PFGE带型,其中3个PFGE型的菌株数超过1株。结论北京市鼠伤寒沙门菌分离株多重耐药较为严重,此次PFGE型别较多,且存在差异明显的多个克隆系,但同一PFGE型菌株的耐药谱较为接近。     

急性感染性腹泻沙门菌分离株的耐药谱及其相关基因分析

目的分析上海地区急性感染性腹泻患者沙门菌的耐药谱及其耐药基因携带情况,为临床治疗提供参考。方法对400例急性腹泻患者粪便样本进行细菌培养,疑似菌株采用Vitek MS质谱仪进行细菌鉴定及血清分型,采用最小抑菌浓度(MIC)法测定沙门菌对15种常用抗菌药物的敏感性,并采用聚合酶链反应(PCR)检测菌株相关耐药基因的携带情况。结果 22株沙门菌分离株主要的血清型为鼠伤寒沙门菌(36.4%,8/22)、肠炎沙门菌(27.3%,6/22)和伦敦沙门菌(18.2%,4/22)。22株沙门菌分离株对氨苄西林-舒巴坦的耐药率最高(95.5%),以下依次为氨苄西林、左氧氟沙星、复方磺胺甲噁唑、环丙沙星-头孢噻肟-庆大霉素、头孢唑林-头孢呋辛-头孢他啶、阿米卡星;但对于哌拉西林-他唑巴坦和亚胺培南则全部敏感。β-内酰胺类药物耐药株中blaTEM-1和blaDHA基因的携带率为23.8%(5/21);氨基糖苷类药物耐药株中aadA1基因检测携带率为25%(1/4);喹诺酮耐药菌株中qyrA4基因、qnrA基因、qnrB基因、qnrS基因、parC基因携带率分别为47.1%(8/17)、5.9%(1/17)、11.7%(2/17)、17.6%(3/17)、58.8%(10/17);磺胺类耐药株中sul I基因的携带率为66.7%(4/6)。结论分离自急性感染性腹泻患者粪便样本的沙门菌总体耐药率较高,对不同药物的耐药率有差异,耐药菌株携带的耐药基因与国内其他地区有所不同,提示沙门菌耐药表型和耐药机制复杂,临床需要进行相关检测并采取个体化精准治疗。     

2014－2018年山东省青岛市腹泻病例中沙门菌分子分型及耐药分析

目的分析山东省青岛市2014 — 2018年腹泻病例中沙门菌的分子分型及耐药状况,为沙门菌引起的腹泻性疾病的预警、防控、溯源及抗生素的合理应用提供科学依据。方法对青岛市 2014 — 2018 年腹泻病例中分离的52株沙门菌采用微量肉汤稀释法进行耐药检测;应用脉冲场凝胶电泳（PFGE）进行分子分型,运用BioNumeries 7.6软件分析菌株之间的相似度。结果52株沙门菌以鼠伤寒沙门菌和肠炎沙门菌为主,PFGE分为31种带型,存在多次聚集现象。 分离菌株对氨苄西林耐药率最高（73.08%）,其次为萘啶酸（57.69%）,多重耐药率达44.23%。结论青岛市沙门菌呈散发、多重耐药趋势,总体耐药率较高,耐药谱广泛,应加强溯源及耐药监测。     

江苏省无锡市门诊腹泻患者鼠伤寒沙门菌分子分型和耐药特征研究

目的 了解无锡市腹泻病例分离的鼠伤寒沙门菌分子分型和耐药特征。方法 对无锡市2016—2017年哨点医院分离的26株鼠伤寒沙门菌采用微量肉汤稀释法测定菌株对9类14种抗菌药物的敏感性;选择两株多重耐药的菌株（SM699：耐7类;SM912：耐4类）进行全基因组二代测序,用生物信息学方法研究其耐药的遗传学基础和多位点序列分型;采用脉冲场凝胶电泳（PFGE）分析菌株同源性。结果 26株鼠伤寒沙门菌对亚胺培南均敏感,对其他13种抗菌药物呈现不同程度的耐药（3.8%～65.4%）。耐药率排在前3位的为四环素（65.4%,17/26）、氨苄西林（61.5%,16/26）、萘啶酸（42.3%,11/26）。20株菌至少对1类及以上抗菌药物耐药（76.9%,20/26）,共产生15种耐药表型,有14株菌为多重耐药菌株（53.8%,14/26）。全基因组二代测序结果表明,SM699和SM912分别携带23种和9种耐药基因,可介导对相应抗菌药物的耐药,耐药基因与耐药表型基本一致。菌株SM699的gyrA基因突变可介导喹诺酮类耐药。两株菌均为ST34型,属于近缘克隆株。26株菌产生23种PFGE带型,相似...     

鼠伤寒沙门菌对喹诺酮类耐药机制的研究

目的检测鼠伤寒沙门菌（STM）对喹诺酮类药物的耐药性及耐药机制的分析。方法收集2004年7月1日-10月31日武汉地区4所大型医院的门诊腹泻病人的粪便进行分离培养出鼠伤寒沙门菌33株。琼脂稀释法测其对喹诺酮类药物的MIC，并抽提此菌的基因组DNA，用PCR方法检测喹诺酮类抗菌药作用于鼠伤寒沙门菌的靶位点：Ⅱ型拓扑异构酶，即DNA促旋酶和拓扑异构酶Ⅳ上的基因片段（gyrA，gyrB，parC，parE）突变情况。结果33株鼠伤寒沙门菌中有24株对环丙沙星产生了很强的耐药性（MIC值4～16mg／L），耐药率达72．7％。24株耐药株中gyrA和parC的突变比较常见，其中gyrA位点都存在突变点，且双重突变占92％，并协同parC的点突变造成高水平的耐药；gyrB和parE的突变很少见，本研究中有少数高水平耐药株的parE和gyrB位点发现可疑的碱基插入。结论研究结果表明武汉地区社区内鼠伤寒沙门菌感染对喹诺酮类药物的耐药性严重，其主要机制是喹诺酮类耐药决定区（QRDR）的基因突变，特别是多个位点同时突变导致高水平耐药。     

2015年北京一起鼠伤寒沙门菌暴发流行的病原学检测分析

2015年5月北京一家大型企业发生聚集性腹泻疫情,流行病学调查后收集现场样本,经过实验室检测确认该次疫情为鼠伤寒沙门菌暴发流行。分离到的18株鼠伤寒沙门菌脉冲场凝胶电泳(PFGE)图谱带型一致,在北京市沙门菌PFGE数据库中未发现相同带型。药物敏感试验结果显示有一株菌株对12种抗生素耐药。这种耐药模式的出现提示需加强耐药监测。     

腹泻患者沙门菌血清型分布及耐药特征分析

目的了解肠道门诊腹泻患者中沙门菌的血清型分布及耐药特征。方法收集2015年4月至2016年4月北京友谊医院肠道门诊分离的沙门菌及沙门菌感染相关资料,进行沙门菌的血清分型并检测菌株对临床常用10种抗生素的耐药性。结果 3 068例腹泻患者粪便中共分离出33株沙门菌,分为10种血清型,主要为肠炎沙门菌和鼠伤寒沙门菌。菌株对氨苄西林和氨苄西林/舒巴坦的耐药率最高,达33.33%,其次为甲氧胺嘧啶/磺胺甲噁唑18.18%,对环丙沙星(12.12%)和头孢曲松(3.03%)、头孢吡肟(3.03%)的耐药率较低。33株菌中发现两重耐药及以上的菌共7株。结论肠炎沙门菌和鼠伤寒沙门菌同为本研究分离菌株中的优势血清型,沙门菌的耐药情况比较严重,尤其是对环丙沙星和三、四代头孢菌素的耐药需引起重视。加强北京地区沙门菌的血清型及耐药监测,能够为肠道传染病的防控提供科学依据,并能指导临床合理使用抗生素,减少耐药菌株特别是多重耐药菌株的出现。     

152株沙门菌临床分离株的耐药性及同源性分析

目的研究本地区沙门菌临床分离株的的耐药状况、分子流行病学特征及对头孢菌素类药物的耐药机制。方法采用琼脂稀释法测定临床常用抗菌药物对沙门菌的最低抑菌浓度（MIC）值,使用 PCR 法和DNA测序法检测头孢菌素耐药基因,脉冲场凝胶电泳（PFGE）法对沙门菌进行同源性分析。结果本地区肠炎沙门菌为主要血清型,占59.9%（91/152）。所有被测菌株均对亚胺培南敏感,对萘啶酸的耐药率最高（86.2%）,其次是氨苄西林（59.9%）、氯霉素（36.2%）和四环素（34.9%）。46.1%（70/152）的沙门菌对3种及以上抗菌药物耐药,其中鼠伤寒沙门菌的多重耐药率比肠炎沙门菌高（85.2% ＞31.9%）。对头孢菌素耐药的14株沙门菌进行PCR扩增并测序均为blaCTX-M型,其中7株为blaCTX-M-55,4株为blaCTX-M-14,2株blaCTX-M-3和1株 blaCTX-M-15。91株肠炎沙门菌分成23个PFGE型,27株鼠伤寒沙门菌分成15个 PFGE 型。PFGE 型别存在多个克隆系。结论本地区沙门菌多重耐药现象严重,产 blaCTX-M型超广谱β-内酰胺酶（ESBLs）是沙门菌对头孢菌素耐药的重要机制。本研究中沙门菌的 ESBLs 基因以 blaCTX-M-55型为主。沙门菌 PFGE 型别多样,存在明显的遗传多样性。     

深圳社区感染沙门菌耐药基因调查与同源性分析

目的 调查深圳社区感染沙门菌耐药特点和分子机制,并进行同源性分析.方法 收集深圳市人民医院2002——2007年临床分离沙门菌共93株,PCR和DNA测序分析沙门菌gyrA、gyrB、parC和parE基因QRDR的突变,PCR检测质粒介导喹诺酮耐药基因qnr和aac(6')-Ib-cr,β内酰胺酶基因blaTEM、blaSHV、blaOXA和blaCTX-M基因,以及Ⅰ类整合子,PFGE对沙门菌进行分子分型.结果 伤寒沙门菌和甲型副伤寒沙门菌对氨苄西林、氯霉素、复方磺胺甲噁唑、头孢曲松和环丙沙尾敏感率为96%～100%;52%(13/25)伤寒沙门菌和95%(61/64)甲型副伤寒沙门菌对萘啶酸耐药.24%(6/25)萘啶酸耐药伤寒沙门菌和94%(60/64)萘啶酸耐药甲型副伤寒沙门菌对环丙沙星敏感性降低(MIC 0.125～μg/ml).75株萘啶酸耐药环丙沙星敏感沙门菌仅GyrA的QRDR均存在第83位或87位单个氨基酸替代,其中Ser83Phe突变占91%(68/75).2株环丙沙星耐药沙门菌在QRDR中均携带GyrA上2个点突变和parC上1个点突变.93株沙门菌均未发现质粒介导的qnr和aac(6')-Ib-cr 基因.1株头孢曲松耐药甲型副伤寒沙门菌检测到blaCTX-M-14基因,且该基因上游存在插入序列ISEcpl.3株多重耐药沙门菌均存在一个1 900 bp的Ⅰ类整合子,其基因盒均为dhfrⅫ-orfF-aadA2,同时携带blaTEM-1或blaOXA-30基因.25株伤寒沙门菌共有22种不同的PFGE带型,64株甲型副伤寒沙门菌的PFGE带型平均相似性为91%.90例患者均系社区感染,6例甲型副伤寒患者发病前30天内曾前往外地旅行.结论 深圳社区感染伤寒和甲型副伤寒沙门菌对萘啶酸耐药率较高,沙门菌GyrA的QRDR点突变是萘啶酸耐药的重要机制,甲型副伤寒沙门菌菌株间遗传同源性极高,来自同一克隆.

Abstract：

Objective To investigate the antimicrobial resistance mechanisms and genetic homogeny of Salmonella from community acquired infections in Shenzhen,China.Methods Ninety-three of Salmonella were isolated from 2002 to 2007 at Shenzhen People's Hospital,China.PCR and DNA sequencing were used to investigate the mutation in QRDR of the gyrA,gyrB,parC and parE.Plasmid mediated quinolone resistance genes including qnr and aac(6')-Ib-cr,β-lactamase genes including blaTEM,blaSHV,blaOXA, blaCTX-M, and class 1 integron were detected. All isolates were typed by PFGE. Results S. enterica typhi and S. enterica paratyphi A were susceptible to ampicillin, chloramphenicol, trimethoprim/sulfamethoxazole, ceftriaxone and ciprofloxacin, with the susceptible rate of 96%-100%. Fifty-two percent (13/25) of S. enterica typhi and 95% (61/64) of S. enterica paratyphi A were resistant to nalidixic acid. Twenty-four percent (6/25) of nalidixic acid-resistant S. enterica typhi and 94% (60/64) of nalidixic acid-resistant S. enterica paratyphi A showed decreased susceptibility to ciprofloxacin (MIC of 0. 125-1 μg/ml).All nalidixic acid-resistant (susceptible to ciprofloxacin ) Salmonella (NARS) isolates had a single substitution in the QRDR of GyrA, and 91% (68/75) of these isolates carried the substitution Ser83Phe in GyrA. Two mutations in the QRDR of GyrA were detected in both of two ciprnfloxacin-resistant Salmonella,with the additional one mutation in the QRDR of parC. Plasmid mediated quinolone resistance genes including qnr and aac(6')-lb-cr were not detected in any isolate. The blaCTX-M-14 gene was detected in a ceftriaxoneresistant isolate of S. enterica paratyphi A, with ISEcpl located on the upstream of it. Three muhidrugresistant strains of Salmonella all carried one 1 900 bp classⅠ integron gene cassette dhfrⅫ-orfF-aadA2,with the additional one β-lactamase gene of blaTEM-1, or blaOXA-30. Twenty-two distinct PFGE patterns were observed among twenty-five S. enterica typhi. The PFGE patterns of sixty-four S. enterica paratyphi A showed limited genetic diversity (average similarity of 91% ). Ninety investigated inpatients were infected in the community. Six patients infected by S. enterica paratyphi A had a travel history before infection. Conclusions Nalidixic acid-resistant S. enterica typhi and S. enterica paratyphi A are highly prevalent in Shenzhen,China. The mutation in the QRDR of GyrA is the prevalent mechanism responsible for the resistance to nalidixic acid in Slmonella. The great genetic similarity among S. enterica paratyphi A isolates indicates endemic disease from the presence of a single clone over 6-year period.     

江阴地区三类整合子在多重耐药铜绿假单胞菌中的流行率及Ⅰ类整合子结构研究

目的了解2005—2006年度我院铜绿假单胞菌对几种常用抗生素的耐药率,分析我院三类整合子的流行情况;明确我院Ⅰ类整合子的基因结构。方法采用药敏纸片法检测100株铜绿假单胞菌对环丙沙星、头孢噻肟、庆大霉素和亚胺培南等的耐药率;用煮沸法提取100株铜绿假单胞菌的DNA模板;应用PCR技术检测三类整合子的流行率及其Ⅰ类整合子结构分析。结果100株铜绿假单胞菌对几种常用药物的耐药率分别为环丙沙星32％、头孢噻肟45％、庆大霉素82％、头孢西丁37％、妥布霉素39％和亚胺培南43％。三类整合子的流行率分别为Ⅰ类53％、Ⅱ类21％、Ⅲ类5％。序列分析表明,在Ⅰ类整合子可变区存在dfrA17、aadA2基因盒。结论4种药物的耐药率都有增高,以庆大霉素最显著,铜绿假单胞菌的多重耐药可能与Ⅰ类整合子的流行有重要的关系。     

High prevalence of the plasmid-mediated quinolone resistance determinant qnrA in multidrug-resistant Enterobacteriaceae from blood cultures in Liverpool, UK

OBJECTIVES: To determine the prevalence of the plasmid-mediated quinolone resistance qnrA gene in a selected collection of blood culture isolates of Enterobacteriaceae resistant to both ciprofloxacin and cefotaxime. METHODS: Over a 29 month period, a total of 47 non-repetitive isolates of Enterobacteriaceae resistant to both ciprofloxacin and cefotaxime were identified. Isolates were screened for the presence of the qnrA gene, class I integrons and bla(ESBL) by PCR. Transferability was examined by conjugation with the sodium azide-resistant Escherichia coli J53. All qnrA-positive isolates were examined for DNA-relatedness by PFGE. RESULTS: A total of 15 of the 47 test isolates (32%) were positive for the qnrA gene, and included single isolates of E. coli and Citrobacter freundii, 4 Klebsiella pneumoniae and 9 Enterobacter cloacae. All 15 qnrA-positive isolates carried class 1 integrons, and 11 the extended-spectrum beta-lactamase gene bla(SHV-12). By PFGE two K. pneumoniae and three E. cloacae, respectively, were considered clonally but not temporally related. Plasmid transfer of quinolone resistance was only achieved with single isolates of K. pneumoniae and E. cloacae. Both plasmids carried class 1 integrons with a pSAL-1-like gene cassette arrangement intl1-aadA2-qacEDelta-sul1. CONCLUSIONS: In this selected group of ciprofloxacin- and cefotaxime-resistant bacteria, carriage of the qnrA gene was high (32%). This compares with <2.0% as demonstrated in worldwide studies of laboratory collections of ciprofloxacin-resistant bacteria. The majority of qnrA-positive isolates in our study originated from high-dependency care units within our hospital, but were shown not to be clonal by PFGE. This is the first report of qnrA-positive Enterobacteriaceae in the United Kingdom.     

Antimicrobial susceptibility and genetic relatedness of Salmonella serovars isolated from animal-derived dog treats in the USA

OBJECTIVES: The objectives of this study were to determine the potential risk of dog treats in transmitting Salmonella to humans in the USA, and to characterize genetic relatedness and antimicrobial resistance among the isolates. METHODS: A total of 158 dog treats derived from pig ears and other animal parts were randomly collected nationwide and assayed for the presence of Salmonella. The Salmonella isolates were characterized using serotyping, pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing. RESULTS: Forty-one percent (65/158) of samples were positive for Salmonella. Eighty-four Salmonella isolates, comprising 24 serotypes, were recovered from the 65 positive samples. Fourteen samples were contaminated with more than one Salmonella serotype. PFGE analysis of 78 Salmonella isolates yielded 64 patterns. S. Infantis with PFGE patterns indistinguishable from those of strains identified in Canadian outbreaks in 1999 were recovered in several dog treat products. The majority of Salmonella isolates were susceptible to the antimicrobials tested; however, resistance was observed to tetracycline (26%), streptomycin (23%), sulfamethoxazole (19%), chloramphenicol (8%) and ampicillin (8%). Twenty-eight (36%) Salmonella isolates were resistant to at least one antimicrobial and 10 (13%) isolates displayed resistance to four or more antimicrobials. Two isolates were identified as S. Typhimurium DT104 with the characteristic penta-resistance phenotype (ampicillin, chloramphenicol, streptomycin, sulfamethoxazole and tetracycline). One S. Brandenburg isolate was resistant to eight antimicrobials. Seven Salmonella isolates also contained class I integrons encoding resistance genes to aminoglycosides, beta-lactam and streptothricin antimicrobials. CONCLUSIONS: The study indicates that animal-derived dog treats in the USA could be a potential source of animal and human infections with Salmonella, including multidrug-resistant Salmonella strains.     

多重耐药不动杆菌16S rRNA甲基化酶和同源性研究

目的 调查2007年7月-2008年5月山西医科大学第二附属医院临床分离的61株多重耐药不动杆菌中介导氨基糖苷类抗生素高水平耐药的16S rRNA甲基化酶基因和Ⅰ类整合子携带耐药基因的分布.方法 利用blaOXA-51基因及16S rRNA-23S rRNA序列进行菌株鉴定,琼脂稀释法测定12种抗菌药物对61株不动杆菌的MIC,PCR筛选6种16S rRNA甲基化酶基因以及整合子基因盒,脉冲场凝胶电泳(PFGE)分析菌株同源性.结果 61株临床分离不动杆菌中55株为鲍曼不动杆菌、3株为3TU不动杆菌、l株13TU不动杆菌、1株醋酸钙不动杆菌、l株溶血不动杆菌.48株不动杆菌对阿米卡星、庆大霉素、妥布霉素均耐药,其中有47株检出armA基因;未检出rmtA、rmtB、rmtC、mad和npmA基因.armA基因阳性的菌株中Ⅰ类整合子阳性27株,分别携带arr-3、accA4、aacCl、catB8、aadA1和dfrA12基因.PFGE条带分析发现47株armA阳性菌株分为5个克隆,其中A、B为主要克隆,分布在我院多个科室中.结论 16S rRNA甲基化酶基因armA在多重耐药不动杆菌中广泛存在,armA基因不位于Ⅰ类整合子中,不动杆菌Ⅰ类整合子携带耐药基因主要介导对氨基糖苷类及氯霉素的耐药性.PFGE结果显示armA基因阳性菌株在我院呈克隆播散,必须采取有效的措施来控制耐药菌的传播.     

Emergence of multidrug-resistant clones of Salmonella Infantis in broiler chickens and humans in Hungary

OBJECTIVES: The characterization of a Salmonella Infantis strain collection that was set up from isolates of animal and human origin obtained in Hungary in recent years. METHODS: All isolates were phage typed. Antimicrobial resistance was tested by the disc diffusion method, while the presence of the antimicrobial resistance genes and class 1 integrons was investigated by PCR. Genetic relatedness of the isolates was tested by PFGE and plasmid profiling. RESULTS: The majority of the isolates representing different parts of Hungary are characterized by phage types 213 and 217 and the nalidixic acid-streptomycin-sulphonamide-tetracycline resistance type. They harbour a class 1 integron with an aadA1 gene in the 855 bp variable region, a tet(A) gene, a >168 kb plasmid and 66% of them represent one genetic clone as determined by XbaI PFGE fingerprinting. CONCLUSIONS: It seems that broiler chickens constitute a reservoir for one large and a few smaller multidrug-resistant Salmonella Infantis clones in Hungary, which might have spread to humans through chicken meat.     

Molecular characterization of ciprofloxacin-resistant Salmonella enterica serovar Typhi and Paratyphi A causing enteric fever in India

OBJECTIVES: To define the genetic characteristics and resistance mechanisms of clinical isolates of Salmonella enterica serovar Typhi (S. Typhi) and S. enterica serovar Paratyphi A (S. Paratyphi A) exhibiting high-level fluoroquinolones resistance. METHODS: Three S. Typhi and two S. Paratyphi A ciprofloxacin-resistant isolates (MICs > 4 mg/L) were compared with isolates with reduced susceptibility to ciprofloxacin (MICs 0.125-1 mg/L) by PFGE, plasmid analysis, presence of integrons and nucleotide changes in topoisomerase genes. RESULTS: In S. Typhi and Paratyphi A, a single gyrA mutation (Ser-83-->Phe or Ser-83-->Tyr) was associated with reduced susceptibility to ciprofloxacin (MICs 0.125-1 mg/L); an additional mutation in parC (Ser-80-->Ile, Ser-80-->Arg, Asp-69-->Glu or Gly-78-->Asp) was accompanied by an increase in ciprofloxacin MIC (> or = 0.5 mg/L). Three mutations conferred ciprofloxacin resistance: two in gyrA (Ser-83-->Phe and Asp-87-->Asn or Asp-87-->Gly) and one in parC. This is the first report of parC mutations in S. Typhi. Ciprofloxacin-resistant S. Typhi and S. Paratyphi A differed in their MICs and mutations in gyrA and parC. Moreover S. Typhi harboured a 50 kb transferable plasmid carrying a class 1 integron (dfrA15/aadA1) that confers resistance to co-trimoxazole and tetracycline but not to ciprofloxacin. PFGE revealed undistinguishable XbaI fragment patterns in ciprofloxacin-resistant S. Typhi as well as in S. Paratyphi A isolates and showed that ciprofloxacin-resistant S. Typhi have emerged from a clonally related isolate with reduced susceptibility to ciprofloxacin after sequential acquisition of a second mutation in gyrA. CONCLUSIONS: To our knowledge this is the first report of molecular characterization of S. Typhi with full resistance to ciprofloxacin. Notably, the presence of a plasmid-borne integron in ciprofloxacin-resistant S. Typhi may lead to a situation of untreatable enteric fever.     

浙江省宁波市多重耐药肯塔基沙门菌的检出及病原学分析

目的 研究浙江省宁波市市售鸡肉与腹泻患者粪便中分离到的多重耐药肯塔基沙门菌的分子分型及耐药谱特征。方法 采用经典血清学方法鉴定肯塔基沙门菌的血清学分型。微量肉汤稀释法检测肯塔基沙门菌对12种抗生素的敏感性。脉冲场凝胶电泳（PFGE）分析不同来源的2株肯塔基沙门菌的分子分型特征。聚合酶链式反应（PCR）检测菌株的耐药基因gyrA、bla_CTX-M14-like、bla_CTX-M15-like、bla_TEM与bla_OXA。结果 2株不同来源的肯塔基沙门菌耐药谱完全相同,均对9种抗生素耐药,为多重耐药沙门菌,且均为ESBLs表型阳性。2株肯塔基沙门菌双酶切（XbaⅠ与BlnⅠ） PFGE分型指纹图完全相同,具有相同PFGE分型。喹诺酮耐药基因gyrA发生83、87位氨基酸密码子点突变;ESBLs决定基因bla_CTX-M14-like、bla_CTX-M15-like、bla_TEM均阳性,bla_OXA阴性。结论 在宁波市售鸡肉样品和临床腹泻患者粪便样品中检出含环丙沙星高水平耐药在内的多重耐药肯塔基沙门菌,PFGE分子型别一致,说明该型多重耐药肯塔基沙门菌已造成散发病例感染。应该加强多重耐药肯塔基沙门菌在禽类养殖业与健康人群中传播的监测。必须规范禽类养殖业对于禽用抗生素的合理使用,防止出现更多的多重耐药沙门菌。     

Characterization of antimicrobial resistance and class 1 and 2 integrons in Salmonella enterica isolates from different sources in Portugal

OBJECTIVES: The antimicrobial resistance profiles of 1183 Salmonella isolates collected during 2002-2003 from several sources (human, food products and environment) were evaluated. The occurrence, distribution and cassette content of class 1 and 2 integrons among the sulphonamide-resistant population, as well as the role of particular clones to the spread of these genetic elements, were investigated. METHODS: The isolates were examined for susceptibility to antimicrobial agents. The characterization of class 1 and 2 integrons was investigated using PCR, PCR-RFLP (restriction fragment length polymorphism) and sequencing in the sulphonamide-resistant isolates. Conjugation assays and clonality analysis by PFGE were performed. RESULTS: The most common resistance phenotypes were to nalidixic acid, tetracycline, streptomycin, sulfamethoxazole and ampicillin (ranging from 31% to 17%). Resistance to sulphonamides (n=200) was associated with resistance to other antimicrobial agents, with 75% of the isolates carrying one or two class 1 integrons while only 3% simultaneously carried class 1 and 2 integrons. Integrons were observed among at least 11 serotypes (mainly Typhimurium) and in a reduced number of PFGE clones (20). Eight class 1 integron types were found, with the aadA genes (aadA1, aadA2 and aadA5) alone or downstream of a trimethoprim (dfrA1, dfrA12 and dfrA17) or a beta-lactamase resistance gene (blaoxa-30) and the blaPSE-1 gene alone. Most of the class 1 integron types were shared by several clones from the same or different serotypes obtained either from humans or food products of animal origin, especially pork products. However, some Typhimurium-specific integrons were found: aadA2 plus blaPSE-1 and blaoxa-30-aadA1. CONCLUSIONS: Apart from the hypothetical contribution of the conjugative transfer of integrons, the incidence of Salmonella carrying these genetic units seems to rely on the ability of certain clones to spread or persist in particular animal niches. Our data suggest that food-producing animals might be simultaneously considered as a reservoir of clones and integrons carrying antibiotic resistance genes, thus making the food chain, especially pork products, a possible source of multidrug-resistant isolates in humans.