High prevalence of acquired quinolone-resistance genes among Enterobacteriaceae from Saudi Arabia with CTX-M-15 β-lactamase

We examined the prevalence of acquired quinolone resistance determinants among Enterobacteriaceae with extended-spectrum β-lactamases (ESBLs) in Riyadh, Saudi Arabia. qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA genes were sought by polymerase chain reaction (PCR) in 160 nonduplicate, clinical Enterobacteriaceae with ESBLs from Prince Salman Hospital in Riyadh during 2009. MICs were determined for qnr- and aac(6')-Ib-cr-positive isolates. Mutations in gyrA and parC were determined for isolates with qnr. ESBL genes were characterized by PCR and sequencing. Among 99 ESBL-producing Escherichia coli, 73% were ciprofloxacin resistant, as were 74% of 61 ESBL-positive Klebsiella pneumoniae. The aac(6')-1b-cr gene was present in 76 ESBL producers, comprising 34 K. pneumoniae and 42 E. coli, whereas qnrA or qnrB genes were found in 21 isolates, all of them also harbouring aac(6')-1b-cr and bla(CTX-M-15), with the latter encoding what was considerably the dominant ESBL in the collection. The qnr-positive isolates harboured a variety of mutation in gyrA and parC but, even with aac(6')-1b-cr also present, high-level ciprofloxacin resistance (MIC >32 μg/mL) was invariably associated with double mutations in gyrA, affecting both Ser83 and Asp87 along with >1 substitution in parC, affecting Ser80 or Glu84.     

从患者胆汁分离的大肠埃希菌中质粒介导的氟喹诺酮类耐药基因的检测

目的 分析浙江省衢州市开化县第二人民医院消化内科胆汁分离的大肠埃希菌的耐药特点并调查质粒介导的喹诺酮类耐药基因的分布情况和流行特点。方法 收集该院消化内科患者2011年1月至2013年6月分离的大肠埃希菌724株,均为非重复性菌株,采用全自动微生物分析仪器VITEK 2 COMPACT进行细菌鉴定及药物敏感性分析,采用聚合酶链反应 (polymerase chain reaction,PCR)分析质粒介导的氟喹诺酮类耐药基因(plasmid-mediated quinolone resistance genes, PMQR) 如qnrA、qnrB、qnrS、aac(6')-Ib-cr和qepA 基因的流行特点。结果 胆源性大肠埃希菌的构成比达18.65%(135/724),其对环丙沙星和左氧氟沙星的耐药率高达61.5%(83/135)和55.6%(75/135),未检出碳青霉烯类抗生素耐药菌株;PCR检测PMQR基因结果显示:135株胆源性大肠埃希菌中,121株 (89.63%) qnrA1 基因阳性,45株(33.33%) qnrB4 基因阳性,32株 (23.70%) qnrB6 基因阳性,43株(31.85%) qnrS1 基因阳性,34株(25.19%) aac(6')-Ib-cr 基因阳性菌株,未检出qepA基因;其中45株(33.33%)同时携带 qnrA1、qnrB4 基因,32株(23.70%)同时携带 qnrA1、qnrB6, 25株(18.52%)同时携带 qnrA1、qnrB4、qnrS1, 21株(15.56%)同时携带 qnrA1、qnrB4、qnrS1、acc(6')-Ib-cr, 12株(100%)同时携带 qnrA1、qnrB6、qnrS1、acc(6')-Ib-cr, 且环丙沙星和左氧氟沙星的耐药率随着PMQR基因组合种类的增多而增多。结论 消化内科胆汁分离的大肠埃希菌氟喹诺酮类抗生素耐药严重,耐药基因主要以 qnrA1为主,qnrB4和qnrB6 次之,且存在多种PMQR基因组合形式,这些潜在播散的氟喹诺酮耐药基因对于临床胆道感染的治疗有很大的挑战。     

Presence of plasmid-mediated quinolone resistance in Klebsiella pneumoniae isolates possessing blaKPC in the United States

The presence of plasmid-mediated quinolone resistance genes [i.e., qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA] was evaluated among 42 bla(KPC)-containing Klebsiella pneumoniae isolates collected in the eastern United States. One isolate carried the bla(KPC-3) and qnrB19 genes on the same conjugative plasmid, whereas another carried the bla(KPC-3) and qnrA1 genes on separate plasmids.     

革兰阴性杆菌临床分离株质粒介导喹诺酮类耐药研究

目的了解质粒介导耐药机制在革兰阴性杆菌临床株对喹诺酮类抗菌药耐药性形成中的作用。方法以PCR方法筛选541株连续分离的所有环丙沙星耐药或中介革兰阴性杆菌中的耐药基因qnrA;以接合试验了解喹诺酮耐药的可转移性;对qnrA阳性株测定氨基糖苷乙酰化酶aac(6′)-Ib-cr基因,分析了gyrA和parC基因的喹诺酮耐药决定区的变异。结果541株革兰阴性杆菌中,7株肠杆菌科细菌qnrA检测阳性,其中4株为阴沟肠杆菌,在不发酵糖菌中未检出qnrA基因。在7株qnrA阳性菌中,4株喹诺酮耐药性可通过质粒转移,接合子对环丙沙星的MIC较受体菌上升12～125倍。4个接合子中环丙沙星MIC较高的2个结合子携带aac(6′)-Ib-cr,7株qnrA阳性临床分离菌中5株耐药决定区gyrA、parC有变异。结论qnrA在肠杆菌属临床分离株中的检出率较高,aac(6′)-Ib-cr基因及靶位改变与qnrA同时存在可能使细菌对喹诺酮类的耐药性进一步上升。     

非发酵菌和环丙沙星敏感肠杆菌科细菌中质粒介导喹诺酮类耐药基因的检测

目的了解3类质粒介导的喹诺酮类耐药基因在浙江省温州地区分离的非发酵菌和环丙沙星敏感肠杆菌科细菌中的分布情况。方法收集2008年1月至2013年6月温州地区分离的非发酵菌和环丙沙星敏感肠杆菌科细菌,共600株,其中非发酵菌419株,环丙沙星敏感肠杆菌科细菌181株。采用聚合酶链反应(PCR)检测qnrA、qnrB、qnrS、aac(6)-Ib以及qepA基因,并通过DNA测序确定qnr基因型和aac(6')-Ib-cr基因变异体;通过接合转移实验研究细菌质粒介导的耐药性传递情况。结果 419株非发酵菌临床株中未检测到qnrA、qnrB、qnrS、aac(6')-Ib和qepA等耐药基因。181株环丙沙星敏感的肠杆菌科细菌临床株中未检到qepA,检到2株qnrA1阳性株,分别为1株肺炎克雷伯菌和1株大肠埃希菌;2株qnrB4阳性株,均为阴沟肠杆菌复合菌;12株检测到aac(6')-Ib,分别为6株大肠埃希菌、3株阴沟肠杆菌复合菌和3株克雷伯菌属细菌。接合转移试验中,2株qnrA1阳性株和1株qnrB4阳性株接合转移成功,12株携带aac(6')-Ib-cr基因的阳性株中4株接合转移成功。结论温州地区,质粒介导的喹诺酮类耐药基因不仅存在于环丙沙星耐药株中,而且还存在于环丙沙星敏感的肠杆菌科细菌中,可能不存在于非发酵菌中。     

Molecular mechanisms of decreased susceptibility to fluoroquinolones in avian Salmonella serovars and their mutants selected during the determination of mutant prevention concentrations

OBJECTIVES: Salmonella enterica isolates of six serovars and mutants obtained during determination of mutant prevention concentrations (MPCs) were investigated for mechanisms of decreased susceptibility to fluoroquinolones. METHODS: The quinolone resistance determining regions (QRDRs) of gyrA, gyrB, parC and parE genes were sequenced. MIC values were determined in the presence/absence of the efflux pump inhibitors carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) or Phe-Arg-beta-naphthylamide (PA beta N). PCR assays for the quinolone resistance genes qnrA, qnrB, qnrS or aac(6')-Ib-cr were applied. The MPC values of ciprofloxacin (MPC(CIP)) were determined for all isolates and selected mutants were investigated for their quinolone resistance mechanisms. RESULTS: In contrast to 11 nalidixic acid-susceptible isolates, 24 nalidixic acid-resistant isolates exhibited single mutations in gyrA (Asp-87 --> Tyr, Gly, Asn or Ser-83 --> Phe, Tyr) or parC (Thr-57 --> Ser). While CCCP had no influence on the MICs, PA beta N decreased the MIC(CIP) values by 1-3 dilution steps and MIC(NAL) values by up to 6 dilution steps. Of the resistance genes investigated, only qnrS was present, in a single Salmonella Infantis isolate. The MPC(CIP) values were 4-64-fold higher than the MICs and ranged between 1-16 and 0.12-1 mg/L, respectively, for isolates resistant or susceptible to nalidixic acid. Only mutants obtained from formerly nalidixic acid-susceptible isolates developed single mutations in gyrA or gyrB. CONCLUSIONS: In field isolates and mutants, target site mutations and efflux seem to be important mechanisms for decreased fluoroquinolone susceptibility. Mutants derived during MPC determination from field isolates already harbouring single-step mutations in gyrA did not exhibit further mutations in any target genes.     

中国九家教学医院肠杆菌科细菌质粒介导的喹诺酮耐药机制研究

目的 研究质粒介导的喹喏酮类的耐药基因qnr和aac(6')-Ib-cr在我国肠杆菌科临床株中的分布状况.方法 从全国9家教学医院收集的421株非重复的4种肠杆菌科细菌[大肠埃希菌(eco)、肺炎克雷伯菌(kpm)、阴沟肠杆菌(ecl)、弗劳地柠檬酸杆菌(cfr)]中,按环丙沙星(CW)≥0.25μg/ml、头孢噻肟(CTX)≥2.0μg/ml、头孢曲松(cno)≥2.0μg/ml的条件筛选出197株,其中cfr30株,ecl 35株,eco 77株,kpm 55株.采用PCR检测筛选菌株的qnrA、qnrB、qnrS和aac(6')-IB质粒介导耐药基因;并以内切酶BtsCI酶切消化aac(6')-Ib PCR阳性产物以确定aac(6')-Ib-cr.接合试验确定喹诺酮耐药的可转移性;用琼脂稀释法测定接合子及其供体菌和受体菌对环丙沙星及其他抗菌药的MIC值.结果 在197株筛选出的肠杆菌科细菌中,qnr共检出83株,总阳性率为42%(83/197),其中qnrA有17株(9%),qnrB有46株(23%),qnrS有24株(12%);qnrA和qnrB同时阳性有2株,qnrB和qnrs同时阳性有2株.aac(6')-Ib共检出90株(46%),aac(6')-Ib-cr共检出36株(18%).qnr和aac(6')-Ib-cr同时阳性的有18株.在ecl、kpn、cfr、eco中,qnr的阳性率分别为66%、66%、63%、6%,aac(6')-Ib-cr阳性检出率分别为9%、22%、27%、17%.qnr和aac(6')-Ib-cr在所有的4种肠杆菌科细菌中的阳性率分别为20%(83/421)和9%(36/421).质粒接合试验获得了13株接合子,环丙沙星对接合子的MIC范围为0.125～1μg/ml,相差8倍;接合子与受体菌相比,CIP的耐药性提高了16～125倍,左氧氟沙星的耐药性提高了16～31倍.结论 在中国,qnr和aac(6')-Ib-cr相关的质粒介导喹诺酮类耐药性在肠杆菌科临床分离株中分布广泛;qnr和aac(6')-Ib-cr能介导喹诺酮低水平耐药,这可能是我国细菌对喹诺酮类耐药性上升迅速的重要原因.     

Quinolone-resistant Shigella flexneri Isolated in a Patient Who Travelled to India

We report a recent case in which ciprofloxacin-resistant Shigella flexneri was isolated from a 23-yr-old female patient with a history of travel to India. Prior to her admission to our internal medicine department, she experienced symptoms of high fever and generalized weakness from continuous watery diarrhea that developed midway during the trip. S. flexneri was isolated from the stool culture. Despite initial treatment with ciprofloxacin, the stool cultures continued to show S. flexneri growth. In the susceptibility test for antibiotics of the quinolone family, the isolate showed resistance to ciprofloxacin (minimum inhibitory concentration [MIC], 8 μg/mL), norfloxacin (MIC, 32 μg/mL), ofloxacin (MIC, 8 μg/mL), nalidixic acid (MIC, 256 μg/mL), and intermediate resistance to levofloxacin (MIC, 4 μg/mL). In molecular studies for quinolone resistance related genes, plasmid borne-quinolone resistance genes such as qnrA, qnrB, qnrS, aac(6')-Ib-cr, qepA, and oqxAB were not detected. Two mutations were observed in gyrA (248C→T, 259G→A) and 1 mutation in parC (239G→T). The molecular characteristics of the isolated S. flexneri showed that the isolate was more similar to the strains isolated from the dysentery outbreak in India than those isolated from Korea.     

肠杆菌科细菌质粒介导喹诺酮耐药基因qnr的研究

目的 调查武汉大学人民医院分离的肠杆菌科细菌中质粒介导喹诺酮类耐药基因qnrA、qnrB、qnrS基因的现状、基因型以及qnr基因阳性菌株所携带的广谱B内酰胺酶基因型.方法 PCR法对179株肠杆菌科细菌(129株大肠埃希菌、37株肺炎克雷伯菌和13株阴沟肠杆菌)进行qnrA、qnrB、qneS基因检测.KB纸片法检测对15种抗菌药的体外抗菌活性.琼脂平皿二倍稀释法检测阳性菌株对环丙沙星的MIC值.质粒接合试验分析qnrA、qnrB、qnrS基因的水平转移能力.对qnr阳性株,检测Ⅰ类整合酶基因及SHV-1、TEM-1、CTX-M、OXA-Ⅰ、OXA-Ⅱ、OXA-Ⅲ、DHA、EBC型β内酰胺酶基因.结果 179株肠杆菌科细菌中,共检测出含qnr基因阳性菌株25株(13.97%),包括6株(3.35%)含有qnrA基因,9株(5.02%)含有qnrB基因,10株(5.59%)含有qnrS基因.阳性株菌均对亚胺培南敏感且对多种抗生素耐药,其中2株qnrA阳性菌株和4株qnrB阳性菌株对喹诺酮类药物敏感.2株qnrA阳性菌株和4株qnrB及qnrS阳性菌株质粒接合成功.23株qnr阳性株Ⅰ类整合酶基因阳性,1株qnrB及qnrS阳性菌株Ⅰ类整合酶基因阴性,14株菌携带TEM-1型广谱β内酰胺酶基因、6株菌携带OXA-Ⅲ型广谱β内酰胺酶基因、7株菌携带EBC型AmpC酶.结论 湖北地区肠杆菌科细菌中存在qnrA、qnrB、qnrS基因的流行,qnr阳性菌株呈多重耐药,且喹诺酮类敏感菌株中有qnr基因的存在.qnr阳性菌株可携带多种广谱p内酰胺酶基因.     

一株产超广谱β-内酰胺酶同时携带qnrB4和aac（6’）-Ib-suzhou型基因大肠埃希菌的鉴定

目的了解1株产超广谱β-内酰胺酶（ESBLs）同时携带qnrB4和aac（6’）-Ib-suzhou型基因大肠埃希菌的耐药机制。方法采用纸片扩散法检测1株分离于血液标本的大肠埃希菌对19种抗菌药物的敏感性,采用聚合酶链反应（PCR）检测6种耐药基因[qnrA、qnrB、qnrC、qnrS、qepA、aac（6’）-Ib],并对qnrB、aac（6’）-Ib基因测序后进行Blast比对分析。结果该菌株除对碳青霉烯类、酶抑制剂复合抗菌药物类敏感外,其余药物全部耐药;PCR发现该菌株同时携带qnrB和aac（6’）-Ib基因,经测序并分别与已在美国国立信息中心[NCBI]登录的DQ303921（qnrB4）和EF375621[aac（6’）-Ib-suzhou]型比对,同源性均〉99％。结论该菌株多重耐药的机制与产ESBLs及携带qnrB4和aac（6’）-Ib基因有关。     

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。     

Rapid detection of qnr and qepA plasmid-mediated quinolone resistance genes using real-time PCR

Plasmid-mediated quinolone resistance genes in clinical strains cannot be detected by phenotypic traits but require gene detection. We developed a multiplex real-time polymerase chain reaction (PCR) assay using high-resolution melting master mix with ResoLight dye to detect qnr genes and a simplex real-time PCR assay using SYBR Green I to detect qepA genes. Using qnr-positive and qepA1-positive control strains, the ResoLight method was able to rapidly identify qnrA, qnrB, qnrS, qnrC, and qnrD genes; the SYBR Green I method identified qepA genes. Among 118 extended spectrum beta-lactamase-producing Enterobacteriaceae isolates, the 2 new assays efficiently detected and identified qnr in 9 strains, but no qepA gene. To our knowledge, this is the first study describing the detection of all 5 qnr and qepA genes using real-time PCR. The 2 tests constitute a significant step forward for screening for plasmid quinolone resistance genes in clinical strains.     

Decreased susceptibility to ciprofloxacin among Shigella isolates in the United States, 2006 to 2009

We characterized 20 Shigella isolates with decreased susceptibility to fluoroquinolones. Most patients (80%) from whom a travel history was obtained reported travel to South or Southeast Asia. Mutations within the quinolone resistance determining regions of gyrA and parC and plasmid-mediated resistance determinants (qnrB, qnrS, and aac(6')-Ib-cr) were identified. The rise in antimicrobial resistance among Shigella isolates may necessitate the increased use of extended-spectrum cephalosporins or macrolides in some patients.     

志贺菌gyrA、parC基因突变与喹诺酮类耐药

目的探讨DNA旋转酶A亚单位（gyrA）和拓扑异构酶Ⅳ C亚单位（parC）基因突变与志贺菌耐喹诺酮类药物的相关性。方法用聚合酶链反应（PCR）检测志贺菌喹诺酮耐药决定区（QRDR）相关gyrA、parC基因并挑选11株菌扩增片段进行DNA测序,分析突变位点与药敏结果的关系。结果11株扩增片段测序结果显示,9株耐萘啶酸菌均在gyrA83位发生有意义突变TCG（Ser）→TTG（Leu）,宋内志贺菌未发生parC基因突变,5株耐萘啶酸、诺氟沙星和／或环丙沙星中介敏感福氏志贺菌在parC80位发生有意义突变AGC（Ser）→ATc（Ile）。结论志贺菌对喹诺酮类药物耐药严重,福氏志贺菌比宋内志贺菌更耐此类药物,靶酶基因突变是其耐喹诺酮类药物的主要机制之一,gyrA Ser83→Leu突变是导致志贺菌临床株对萘啶酸耐药的关键突变。parC基因突变在gyrA基因突变的基础上才会发生,parC突变可能引起诺氟沙星和／或环丙沙星不敏感。     

肺炎克雷伯菌中qnr基因检测

目的了解质粒介导的喹诺酮类耐药基因qnr在肺炎克雷伯菌中流行及与ESBLs及对环丙沙星耐药的相关性.方法 纸片扩散法检测药物敏感性,双纸片协同试验检测ESBLs.PCR方法检测qnr基因.结果 62株非重复的肺炎克雷伯菌中,ESBLs阳性率为75.8%(47/62),环丙沙星敏感率为45.2%(28/62),qnr总阳性率为53.2%(42/62).单纯qnrA阳性5株(8%),qnrB9株(14.5%),qnrS10株(16.1%).同时2种qnr基因阳性9株(14.5%),qnrA和qnrB基因阳性1株(1.6%),qnrA和qnrS基因3株(4.8%),qnrB和qnrS基因5株(8%).在环丙沙星耐药株和敏感株中,qnr基因的阳性率分别为58.8%(20/34)和46.7%(13/28).在ESBLs阳性菌株和阴性菌中,qnr的阳性率分别为68%(32/47)和6.6%(1/15).结论 qnr基因主要分布在产ESBLs的肺炎克雷伯菌,与环丙沙星耐药与否无相关.     

Prevalence of qnr genes in Salmonella in France

OBJECTIVES: To detect the qnrA, qnrB and qnrS genes among Salmonella isolates received at the French National Reference Centre for Salmonella in Paris, France. METHODS: Antibiotic susceptibility was determined by disc diffusion for 499 Salmonella isolates including 320 Salmonella Typhimurium, 100 Salmonella Enteritidis and 79 Salmonella Hadar collected in 2002. Amplification with specific primers of qnrA, qnrB and qnrS genes was performed for all Salmonella Typhimurium, Salmonella Enteritidis and Salmonella Hadar isolates resistant to quinolones and for 17 additional isolates that produced expanded-spectrum beta-lactamases (ESBLs). RESULTS: Prevalence of quinolone resistance was 3.75%, 11% and 79.7% for Salmonella Typhimurium, Salmonella Enteritidis and Salmonella Hadar serovars, respectively. A single isolate (0.2%) was qnrA-positive (QnrA1 determinant) being a Salmonella serovar Concord carrying also the ESBL gene bla(CTX-M-15). This strain was probably from East Africa. No qnrB or qnrS genes were identified. CONCLUSIONS: Whereas plasmid-mediated quinolone resistance of the Qnr type is emerging in Enterobacteriaceae worldwide, it remains rare in Salmonella in France.     

Investigation of qnr and aac(6')-Ib-cr in Enterobacter cloacae isolates from Anhui Province, China

Eighty-one Enterobacter cloacae isolates collected from 20 hospitals in Anhui Province, China, from January to August 2005 were screened for plasmid-mediated quinolone resistance determinants by polymerase chain reaction and sequencing. qnrA1, qnrB4, qnrS1, and aac(6')-Ib-cr were present in 6.2% (5/81), 6.2% (5/81), 8.6% (7/81), and 3.7% (3/81) of those isolates, respectively.     

Analysis of the mechanisms of quinolone resistance in clinical isolates of Citrobacter freundii

The presence of gyrA, gyrB and/or parC mutations, quinolone uptake, outer membrane protein profiles and epidemiological relationship were studied in 12 clinical isolates of Citrobacter freundii. No alterations were observed in the gyrB gene of any of the strains, or gyrA or parC of the four quinolone-susceptible strains (nalidixic acid MIC of 2-4 mg/L, and a ciprofloxacin MIC of 0.006-0.06 mg/L). The quinolone-resistant strains were classified into two groups: one group (group A) composed of strains resistant to nalidixic acid but not to ciprofloxacin and another (group B) including those resistant to both antibiotics with a mutation at codon 83 of the gyrA gene (Thr-->Ile), but no alteration in either parC or gyrB genes. In group B, three of the four resistant isolates, with a nalidixic acid MIC > 1024 mg/L and ciprofloxacin MIC of 8-32 mg/L, showed concomitant mutations at codons 83 and 87 of the gyrA gene (Thr-->Ile and Asp-->Tyr, respectively) as well as a single mutation in codon 80 of the parC gene (Ser-->Ile). The fourth isolate did not possess the mutation at codon 87 of gyrA. Two strains belong to the same clone and, although they had the same type of mutations in the gyrA and parC genes, showed different MICs of ciprofloxacin. This difference was related to an efflux pump mechanism. Mutations in the gyrA and parC genes play the main role in quinolone resistance development in Citrobacter freundii, although other factors such as overexpression of efflux pumps can play a complementary role and thus modulate the final quinolone MIC.     

Emergence of Proteus mirabilis harboring blaKPC-2 and qnrD in a Chinese Hospital

Nineteen carbapenem-nonsusceptible Proteus mirabilis isolates were recovered from intensive care units in the Second Affiliated Hospital of Zhejiang University during a 3-month period. The isolates showed a high level of resistance against ciprofloxacin, in addition to their resistance against the carbapenems. Pulsed-field gel electrophoresis (PFGE) analysis showed that these isolates belonged to three clonal strains. PCRs and DNA sequence analysis of the carbapenemase and other β-lactamase genes indicated that all the isolates harbored the bla(KPC-2) gene. Twelve of 19 isolates harbored the plasmid-mediated quinolone resistance (PMQR) genes, both the qnrD and aac(6')-Ib-cr genes. Eight representative isolates with high levels of quinolone resistance carried the similar mutation profiles of S83I in gyrA, E466D in gyrB, and S80I in parC. Reduced carbapenem susceptibility was transferred to Escherichia coli (EC600) in a conjugation experiment, while the quinolone resistance was not. DNA hybridization showed that qnrD was located on a plasmid of approximately 4.5 kb. In summary, large clonally related isolates of KPC-2-producing P. mirabilis emerged in a Chinese hospital, and qnrD was detected in KPC-producing P. mirabilis for the first time.