Plasmid-mediated quinolone resistance in Australia

The aim of this study was to search for plasmid-encoded quinolone resistance determinants QnrA and QnrS in fluoroquinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing enterobacterial isolates recovered in Sydney, Australia, in 2002. Twenty-three fluoroquinolone-resistant, of which 16 were also ESBL-positive, enterobacterial and nonrelated isolates were studied. PCR with primers specific for qnrA and qnrS genes and primers specific for a series of ESBL genes were used. A qnrA gene was identified in two ESBL-positive isolates, whereas no qnrS-positive strain was found. The QnrA1 determinant was identified in an Enterobacter cloacae isolate and in a carbapenem-resistant Klebsiella pneumoniae isolate, both of which expressed the same ESBL SHV- 12. Whereas no plasmid was identified in the E. cloacae isolate, K. pneumoniae K149 possessed two conjugative plasmids, one that harbored the qnrA and bla (SHV)-12 genes whereas the other expressed the carbapenemase gene bla (IMP-4). The qnrA gene, was located in both cases downstream of the orf513 recombinase gene and upstream of the qnrA1 gene, a structure identical to that found in sul1-type integron In36 and qnrA-positive strains from Shanghai, China. However, the gene cassettes of the sul1-type integrons were different. This study identified the first plasmid-mediated quinolone resistance determinant in Enterobacteriaceae in Australia.     

水环境分离细菌及临床分离弗劳地柠檬酸杆菌中喹诺酮耐药基因qnr及aac(6')-Ⅰ b-cr的检测

目的 调查水环境分离细菌及临床分离弗劳地柠檬酸杆菌中喹诺酮耐药基因qnr和aac(6')-Ⅰ b-cr的流行情况及qnr基因型分布.方法 从杭州10个不同的水域中分离细菌,从4个城市的多家医院收集弗劳地柠檬酸杆菌临床菌株.琼脂稀释法测定环丙沙星、左氧氟沙星和萘啶酸对细菌的最低抑菌浓度(MIC).PCR方法检测细菌中qnrA、qnrB、qnrS及aac(6')-Ⅰ b-cr基因.对PCR产物进行测序及序列分析,确定各基因型别.结果 从水环境分离到78株革兰阴性杆菌(包括33株肠杆菌科细菌、21株气单胞菌属、10株不动杆菌属、10株假单胞菌属、2株产碱杆菌属和2株邻单胞菌属细菌).10株弗劳地柠檬酸杆菌中有8株qnrB基因阳性;9株大肠埃希菌中qnrS1和aac(6')-Ⅰb-cr基因阳性各1株;1株斑点气单胞菌(Aeromonas punctata)qnrS2阳性.临床分离的103株弗劳地柠檬酸杆菌中,qnr基因检出75株(72.8%),其中qnrA1有3株(2.9%),qnrB有65株(63.1%),qnrS2有1株(1.0%),qnrA1合并qnrB阳性5株(4.8%),qnrS1合并qnrB阳性1株;aa47(6')一Ⅰ b检出33株(32.0%),其中12株(11.6%)存在-cr变异体.qnrB的基因型以qnrB9、qnrB8和qnrB6为主.结论 首次在欧洲以外地区分离到携带qnrS2基因的气单胞菌属细菌.水环境及临床分离的弗劳地柠檬酸杆菌中qnrB基因的携带率非常高,后者同时有较高的aac(6')-Ⅰ b-cr携带率.弗劳地柠檬酸杆菌中qnrB基因的亚型以qnrB9、qnrB8和qnrB6最为常见.     

High rates of plasmid-mediated quinolone resistance QnrB variants among ciprofloxacin-resistant Escherichia coli and Klebsiella pneumoniae from urinary tract infections in Korea

The aims of this study were to investigate the prevalence of qnrA, qnrB, and qnrS determinants and their molecular characteristics in ciprofloxacin-resistant isolates of Escherichia coli and Klebsiella pneumoniae from urinary tract infections (UTI) in Korea. A total of 202 nonduplicated clinical isolates of ciprofloxacin-resistant E. coli (n = 143) and K. pneumoniae (n = 59) were collected between July 2005 and August 2006. The qnr determinant screening was carried out by PCR amplification of qnrA, qnrB, and qnrS, and all positive results were confirmed by direct sequencing of the PCR products. For qnr-positive strains and their conjugants, antimicrobial susceptibility tests and pulsed-field gel electrophoresis (PFGE) were performed. The qnrB gene was detected in 41 of the 202 isolates. Among 33 of 59 (55.9%) K. pneumoniae isolates showing qnrB, 29 isolates contained the qnrB4 gene, 3 isolates had the qnrB2 gene, and 1 isolate had the qnrB6 gene. All 8 (5.6%) of the qnrB-positive isolates among the 143 E. coli strains possessed the qnrB4 gene. The minimum inhibitory concentrations (MICs) of ciprofloxacin for the transconjugants were 0.03-2 mug/ml, representing an increase of 4- to 256-fold relative to the recipient, E. coli J53Az(r). Resistances to various other antimicrobial agents also were transferred with the plasmid. The PFGE analysis revealed indistinguishable or closely related patterns in several strains and highly diverse patterns in general. QnrB variants, especially the qnrB4 subtype, are highly prevalent in ciprofloxacin-resistant E. coli and K. pneumoniae from UTI in Korea. The emergence of plasmid-mediated quinolone resistance may contribute by several means to the rapid increase in bacterial resistance to these drugs.     

Occurrence of qnrA-positive clinical isolates in French teaching hospitals during 2002–2005

Bacteria harbouring the novel qnrA plasmid-mediated mechanism of quinolone resistance have been described in different countries, but the frequency of their occurrence has not been investigated. In total, 1,468 clinical isolates of Enterobacteriaceae with quinolone resistance or extended-spectrum beta-lactamase (ESBL) phenotypes were collected from eight teaching hospitals in France during 2002-2005 and screened for qnrA. Overall, 28 isolates (22 Enterobacter cloacae, three Klebsiella pneumoniae, one Citrobacter freundii, one Klebsiella oxytoca and one Proteus mirabilis) were positive for qnrA, representing 1.9% of all isolates, 3.3% of ESBL-producing isolates (22% of the E. cloacae isolates) and 0% of non-ESBL-producing isolates. The prevalence of qnrA among consecutive ESBL-producing isolates in 2004 from the eight hospitals was 2.8% (18/639). Of the qnrA-positive isolates, 100% were intermediately-resistant or resistant to nalidixic acid, and 75% to ciprofloxacin. Twenty-one of the 22 qnrA-positive E. cloacae isolates were obtained from two hospitals in the Paris area, and molecular typing and plasmid content analysis showed clonal relationships for five, three and two isolates, respectively. The qnrA genetic environment was similar to that of the In36 integron. The remaining two isolates had qnrA variants (30 and 29 nucleotide differences, respectively, compared with the original sequence) and an unknown genetic environment. The ESBL gene associated with qnrA was bla(SHV-12) in most of the isolates, but bla(PER-1) and bla(SHV-2a) were found in two isolates. In France, it appears that qnrA-positive isolates are predominantly E. cloacae isolates producing SHV-12, and may be associated with the dissemination of an In36-like integron.     

海藻希瓦菌中发现一种新的qnrA7基因亚型

目的 研究海藻希瓦菌中质粒介导的喹诺酮类耐药基因的分布和特性.方法 PCR检测qnr、qepA、aac(6')Ib-cr基因,阳性产物进行DNA测序以确定其基因型,接合转移试验探讨质粒介导的喹诺酮类耐药基因的体外转移性,E-test法测定菌株MIC,提取质粒对qnrA基因进行初步定位.结果 海藻希瓦菌中检出qnrA基因,为新发现的亚型,命名为qnrA7,GenBank登录号为GQ463707,未检出qnrB、qnrS、qnrC、qnrD、qepA、aac(6')-Ib-cr基因;qnrA7位于约33 kb的质粒上,但体外接合转移试验未成功;该菌对喹诺酮类药物敏感.结论 海藻希瓦菌质粒上检出新的qnrA基因亚型,其作为qnr基因的环境宿主值得关注.     

革兰阴性菌qnrA基因介导的喹诺酮耐药分子机制研究

目的了解革兰阴性菌质粒介导qmA耐药基因的发生率、分子遗传学背景及其阳性株的耐药谱。方法收集2004年4月-2006年4月对萘啶酸耐药的临床分离无重复株共629株，采用特异引物PCR结合测序进行qnrA阳性株的识别，表型确认试验结合PCR检测识别产ESBL或AmpC酶的qnrA阳性株，Kirby-Bauer法和Etest法进行qnrA阳性株的药敏检测，质粒接合转移及Southem杂交检测进行qmA基因的质粒定位，PCR策略克隆携带qnrA基因整合子基因结构并进行引物步移测序。结果qnrA阳性株的总检出率为1.9％（12／629）。菌种分布为肺炎克雷伯菌2．2％（3／138），阴沟肠杆菌17．1％（6／35），产气肠杆菌9．1％（1／11），枸橼酸杆菌属12．5％（1／8），沙门菌属14．3％（1／7）。qnrA基因定位在80～180kb大小质粒上的su／1型Ⅰ类整合子基因结构中。其中4株菌qnrA基因定位在整合子In37上，另外8株菌qnrA基因定位在一种新型的整合子InX上。所有qnrA阳性株均产ESBL，并具有可转移多重耐药的特征。结论广东地区喹诺酮抗菌药耐药株中存在着质粒介导的耐药机制，但发生率较低；其耐药基因qnrA的水平传播能力有可能导致细菌耐药性的播散。     

Fecal colonization of Enterobacteriaceae carrying plasmid-mediated quinolone resistance determinants in Korea

The aims of the current study were to investigate the prevalence and molecular characteristics of plasmid-mediated quinolone resistance (PMQR) genes from colonizing fecal organisms and to compare the incidence and subtype of these genes according to bacterial species and hospital at five tertiary-care hospitals in Korea. A total of 500 nonduplicated clinical isolates of Enterobacteriaceae were obtained from fecal specimens at five tertiary-care hospitals between March and May 2008. The PMQR genes (qnrA, qnrB, qnrS, aac(6')-Ib-cr, and qepA) were amplified by PCR and confirmed by direct sequencing of the PCR products. A total of 83 (16.6%) qnr-positive isolates were detected. The prevalence rates of qnrA, qnrB, and qnrS were 1.4%, 13.6%, and 1.6%, respectively. The species distributions of qnrB-positive isolates were Klebsiella pneumoniae (37/109; 33.9%), Citrobacter freundii (10/34; 29.4%), Citrobacter braakii (8/13; 61.5%), and Escherichia coli (8/275; 2.9%). Sixteen subtypes of qnrB were detected, including seven novel variants. The prevalences of aac(6')-Ib-cr and qepA were 15.6% (n=78) and 0.6% (n=3), respectively. The aac(6')-Ib-cr gene was detected in 39 (47.0%) of 83 qnr-positive isolates and 39 (9.4%) of 417 qnr-negative isolates There was one qepA variant containing a novel mutation (Ala231Val). The prevalence of PMQR genes was high in Enterobacteriaceae from stool specimens in Korea, and there was a close relation between qnr and aac(6')-Ib-cr.     

Prevalence and characterization of plasmid-mediated quinolone resistance genes in extended-spectrum β-lactamase-producing Enterobacteriaceae isolates in Mexico

The objectives of this study were to investigate the prevalence of plasmid-mediated quinolone resistance genes in a collection of 226 extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae isolates and characterize the qnr-positive isolates. The rate of qnr-positive isolates was 21.6% (49/226), 49.5% for aac(6')-Ib-cr (112/226), and 1.7% for qepA1 (4/226). Those isolates carried qnr genes corresponding to types qnrB (71.4%), qnrS1 (24.4%), and qnrA1 (18.3%). The distribution among bacterial species was as follows: 55.8% (19/34) to Enterobacter cloacae, 50% (28/56) to Klebsiella pneumoniae, and 1.4% (2/136) to Escherichia coli. The characterization of qnr-positive isolates indicated the ESBL SHV-types as the most prevalent (81.6%), including the ESBLs SHV-12, SHV-5, and SHV-2a, followed by CTX-M-15 (44.9%) and TLA-1 (8.1%). In addition, for qnr-positive isolates, the prevalence of aac(6')-Ib-cr was 55.1%, but qepA was not identified. Alterations at codons Ser-83 and Asp-87 in GyrA and at codons Ser-80 in ParC were observed in 69% and 80% of the qnr-positive isolates, respectively. The analysis of the transconjugants revealed a cotransmission of bla(CTX-M-15) with qepA1 or aac(6')-Ib-cr and/or qnrA1 and bla(SHV-type) with qnrB5 and qnrB6 genes. To conclude, these findings indicate a high prevalence of qnr and aac(6')-Ib-cr among ESBL-producing isolates from Mexican hospitals and point to the wide spread of qnr-like determinants associated to ESBLs SHV- and CTX-M-type in Mexican clinical isolates.     

Emergence of multidrug-resistant NDM-1-producing Gram-negative bacteria in Bangladesh

The main objective of this study was to investigate the prevalence of bla (NDM-1) in Gram-negative bacteria in Bangladesh. In October 2010 at the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) laboratories, 1,816 consecutive clinical samples were tested for imipenem-resistant Gram-negative organisms. Imipenem-resistant isolates were tested for the bla (NDM-1) gene. Among 403 isolates, 14 (3.5?%) were positive for bla (NDM-1), and the predominant species were Klebsiella pneumoniae, Acinetobacter baumannii, and Escherichia coli. All bla (NDM-1)-positive isolates were resistant to multiple antibiotics. Among β-lactamase genes, bla (CTX-M-1-group) was detected in ten isolates (eight bla (CTX-M-15)), bla (OXA-1-group) in six, bla (TEM) in nine, bla (SHV) in seven, and bla (VIM) and bla (CMY) in two isolates each. The 16S rRNA methylase gene, armA, was detected in five?K. pneumoniae isolates and in one E. coli isolate. rmtB and rmtC were detected in a Citrobacter freundii and two?K. pneumoniae isolates, respectively. qnr genes were detected in two?K. pneumoniae isolates (one qnrB and one qnrS) and in an E. coli isolate (qnrA). Transferable plasmids (60-100?MDa) carrying bla (NDM-1) were detected in 7 of the 11 plasmid-containing isolates. Pulsed-field gel electrophoresis (PFGE) analysis grouped K. pneumoniae isolates into three clusters, while E. coli isolates differed significantly from each other. This study reports that approximately 3.5?% of Gram-negative clinical isolates in Bangladesh are NDM-1-producing.     

Molecular epidemiology of ciprofloxacin-resistant extended-spectrum β-lactamase-producing Klebsiella pneumoniae in Taiwan

Fluoroquinolone resistance in extended-spectrum β-lactamases (ESBL)-producing isolates results in very few antimicrobial treatment options. In Taiwan's Surveillance of Antimicrobial Resistance (TSAR) III program, 124 (52.8%) cases of ESBL-producing Klebsiella pneumoniae (ESBL-KP) were resistant to ciprofloxacin. The prevalence of plasmid-mediated quinolone resistance (PMQR) determinants and chromosomal quinolone resistance-determining regions (QRDR) of gyrA and parC genes among ESBL-KP isolates was assessed via PCR sequencing. Chromosomal QRDR mutations were present in most of the 123 (96.8%) cases of ciprofloxacin-resistant ESBL-KP isolates. Sixty-six (53.2%) isolates had at least one PMQR gene. qnrB2, qnrB4, and qnrS1 were detected in 26, 19, and 13 isolates, respectively, whereas qnrA, qnrC, and qnrD were not detected. ESBL genes were transferable via conjugation with either aac(6')Ib-cr or qnrB in 63.6% of the isolates carrying PMQR genes. QnrB was associated with either CTX-M-15 or SHV-12, and aac(6')Ib-cr was linked to CTX-M-3 or CTX-M-14 in plasmids. qnrS did not co-transfer with ESBL genes. Clonal spread of PMQR genes harboring ESBL-KP isolates was observed in three hospitals. QnrA, which is common in Asia, was unexpectedly absent in ESBL-KP in Taiwan. Aside from transmission via clonal spread for ciprofloxacin-resistant ESBL-KP, concomitant transference of PMQR genes with either bla(CTX-M) or bla(SHV) via plasmid was common.     

大肠埃希菌尿液分离株中检出gyrA基因新变异株

目的 调查大肠埃希菌尿液分离株中喹诺酮类耐药相关基因的存在与变化状况.方法 收集宁波市第一医院2008年10月到2009年3月患者尿液标本中分离的大肠埃希菌共28株,采用聚合酶链反应(PCR)及序列分析的方法分析1种染色体介导的喹诺酮类耐药相关基因(gyrA基因)和5种质粒介导的喹诺酮类耐药相关基因[qnrA、qnrB、qnrS、aac(6＇)-Ⅰb、qepA].结果 28株大肠埃希菌检测到1株aac(6＇)-Ⅰb-Cr基因阳性株(经测序比对证实),qnrA、qnrB、qnrS、qepA基因均未检出.gyrA基因83位密码子28株菌都有突变(100.0%),其突变方式为TCG-83→HTG,导致氨基酸从丝氨酸(S)-83→亮氨酸(L);87位密码子22株菌(78.6%)有突变,可分为两种突变方式:21株(75.0%)突变方式为GAC-87→AAC,导致氨基酸从天冬氨酸(D)-87→天冬酰胺(N);5号株gyrA基因(3.6%)为新亚型,其突变方式为GAC-87→TAC,导致氨基酸从天冬氨酸(D)-87→脯氨酸(Y),另6株菌87位密码子无突变.结论 本组大肠埃希菌gyrA基因突变率为100.0%,是喹诺酮类耐药的主要原因.其他耐药相关基因阳性率很低.     

Characterisation and molecular epidemiology of extended-spectrum β-lactamase-producing Enterobacter cloacae isolated from a district teaching hospital in Taiwan

Enterobacter cloacae (n = 110) isolates from a district hospital in Taiwan were screened for extended-spectrum beta-lactamases (ESBLs). In total, 17 ESBL-producers were identified, based on the combination-disk synergy test using cefotaxime and ceftazidime +/- clavulanic acid. Investigation of ESBL genes in 33 ceftazidime-resistant isolates revealed the SHV-12 gene in the same 17 ESBL-producers. In addition, one isolate also carried the CTX-M-3 gene, and two isolates also carried the CTX-M-9 gene. No major epidemic clone of ESBL-producers was identified by pulsed-field gel electrophoresis. Routine screening for the ESBL phenotype, focusing on ceftazidime-resistant E. cloacae, should be undertaken in this area.     

Epidemiology of extended-spectrum beta-lactamase-producing Enterobacter isolates in a Spanish hospital during a 12-year period

Fifteen Enterobacter clinical isolates (11 Enterobacter cloacae isolates, 3 Enterobacter aerogenes isolates, and 1 Enterobacter gergoviae isolate), representing 0.4% of all Enterobacter isolates recovered in our hospital from 1989 to 2000, were suspected of harboring an extended-spectrum beta-lactamase (ESBL). These isolates were recovered from 14 different patients. ESBLs were transferred by conjugation into an Escherichia coli recipient strain. Pulsed-field gel electrophoresis (PFGE) revealed a single clone of E. aerogenes and six different clones of E. cloacae. Four of these E. cloacae clonal types were represented by only one isolate each, but the other two were represented by three and four isolates, respectively. Isoelectric focusing, susceptibility phenotyping, PCR analysis, and sequencing demonstrated the presence of three different ESBLs. The most frequent was the recently characterized CTX-M-10 ESBL, which was found in the E. gergoviae isolate and in all but one of the E. cloacae isolates. The remaining E. cloacae isolate harbored a TEM-27 ESBL, and the three E. aerogenes isolates harbored a TEM-24 ESBL. PFGE revealed that our E. aerogenes strain was indistinguishable from the French TEM-24-producing E. aerogenes endemic clone. Although a low prevalence of ESBL-producing Enterobacter isolates was found in our institution over a 12-year period, a diversity of nonepidemic E. cloacae clones was detected, as was the persistence of the CTX-M-10 beta-lactamase. The presence of the TEM-24-producing E. aerogenes French clone in our institution also demonstrates the intercountry dissemination of ESBL-producing isolates.     

大肠埃希氏菌的qnrB基因检测与耐药机制研究

目的探索本地区医院大肠埃希氏菌喹诺酮耐药基因的分布及耐药机制。方法采用PCR扩增与测序、基因初步定位、质粒接合转移实验等方法确定喹诺酮耐药的大肠埃希氏菌qnr的基因类型,以分析研究有关的耐药特点与机制。结果各大肠埃希氏菌株中仅qnrB基因阳性,qnrA、qnrS、qnrC、qnrD、qepA、aac（6’）-Ib-cr基因均阴性;并且qnrB基因包括qnrB2、qnrB5、qnrB9、qnrB16、qnrB18、qnrB19和qnrB31等位基因;在这些qnrB等位基因中,qnrB31与qnrB16、qnrB2与qnrB9同源性较高;各qnrB等位基因分别位于约21.0 kb至28.0 kb长的质粒上。结论在本地区医院存在不同的qnrB等位基因流行;实验菌株的喹诺酮耐药与qnrB等位基因结构中LexA-蛋白结合位点共有序列缺失有关。     

Molecular characterization of antimicrobial multi-drug resistance in non-typhoidal Salmonellae from chicken and clam in Mangalore,India

Salmonella enterica has been documented as one of the leading causes of salmonellosis throughout the world and is most commonly associated with the consumption of contaminated food products. Thus, this research was aimed at studying the antimicrobial susceptibility pattern and detection of quinolone resistance in Salmonella spp isolated from food of animal origin. Thirty-six Salmonella isolates comprising 8 from poultry and 28 from seafood (clams) were identified, serotyped and characterized for their antimicrobial susceptibility against 10 different antibiotics. Plasmid DNA was isolated from all the isolates by alkaline lysis, quinolone resistant non-typhoidal S. Weltevreden were examined for mutation in the DNA gyrase coding gene. Among the 36 Salmonella isolates, 20 were S. weltevreden (8 from poultry and 12 from seafood) and 16 were S. Typhimurium (from seafood). All the isolates showed multiple resistance to nalidixic acid, tetracycline, co-trimoxazole and nitrofurantoin, but, interestingly, the isolates were 100% susceptible to ampicillin, chloramphenicol and gentamicin. Resistant isolates from the study carried the genes responsible for resistance to respective antibiotics. The strain S130 isolated in the study showed single point mutation, Asp87Gly, at position 87 in quinolone resistance determining region. It revealed mutation in quinolone resistance determining region as a cause for quinolone resistance in non-typhoidal Salmonellae. The occurrence of genes accountable for plasmid mediated resistance to quinolones (viz., qnrA, qnrB and qnrS) in plasmid of non-typhoidal Salmonellae isolates provides evidence for plasmid mediated quinolone resistance.     

Characterization of extended-spectrum beta-lactamases and qnr plasmid-mediated quinolone resistance in German isolates of Enterobacter species

The objective of this study was to characterize the antimicrobial resistance patterns of 100 clinical isolates of Enterobacter spp. with special regard to the occurrence of extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated quinolone resistance by qnr-determinants. The rate of ESBL- and qnr-positive isolates was 7% and 14%, respectively. Thirteen isolates harbored a qnrA1, and a further isolate harbored a qnrB4 gene. Moreover, qnr-determinants were significantly associated with ESBL-expression. No carbapeneme or tigecycline resistance was detected in the collective tested. To conclude, these data confirm the increase of multiple antimicrobial resistance mechanisms in Enterobacter spp.     

Type 3 fimbriae among enterobacteria and the ability of spermidine to inhibit MR/K hemagglutination.

The distribution of the gene cluster encoding type 3 fimbriae among various isolates of the family Enterobacteriaceae was investigated by using 112 clinical and nonclinical isolates. Closely related DNA sequences were detected in all Klebsiella strains, in most Enterobacter isolates, in a smaller number of Escherichia coli and Salmonella spp., and in a single isolate each of Yersinia enterocolitica and Serratia liquefaciens but not in isolates of Morganella or Providencia species or Serratia marcescens. Except for E. coli and Salmonella strains, the presence of gene sequences was correlated with the phenotypic expression of either the MR/K hemagglutinin or fimbriae that reacted with specific antibodies. In one isolate of Y. enterocolitica the expression of type 3 fimbriae was plasmid determined. The polyamine spermidine was identified as an inhibitor of MR/K hemagglutinating activity, exhibiting an MIC of 1.2 mM. Spermidine inhibited the hemagglutination of 37 MR/K-positive clinical isolates from various genera. However, one clinical isolate of Enterobacter cloacae and most (four of five) nonclinical Klebsiella isolates were not completely inhibited.     

环丙沙星耐药肠杆菌科细菌临床株qnr和aac(6')-Ⅰ b-cr基因的检测

目的 了解温州地区环丙沙星耐药肠杆菌科细菌临床株的qnr、aac(6')-Ⅰ b-cr基因的分布情况.方法 收集2005年8月-2008年4月间温州医学院附属第一医院环丙沙星耐药的肠杆菌科细菌共461株,其中大肠埃希菌370株,阴沟肠杆菌39株,克雷伯菌属细菌52株.应用PCR方法 检测qnr和aac(6')-Ⅰ b幕因,DNA测序检测qnrA、qnrB、qnrS和aac(6')-Ⅰ b-cr基因;接合传递试验方法 探讨细菌质粒介导的耐药性传递情况.结果 461株环丙沙星耐药的肠杆菌科细菌临床株中检出含qnr基因阳性菌株15株(3.25%),包括qnrA基因阳性株5株(4株阴沟肠杆菌和1株解鸟氨酸克雷伯菌)、qnrB基因阳性株4株(2株肺炎克雷伯菌和2株大肠埃希菌)、qnrS基因阳性株6株(2株肺炎克雷伯菌和4株大肠埃希菌);检出52株细菌(包括42株大肠埃希菌、4株阴沟肠杆菌和6株克雷伯菌属细菌)携带aac(6')-Ⅰ b-cr.15株qnr基因阳性的菌株同时携带aac(6')-Ⅰ b-cr,药敏结果 显示对业胺培南敏感但对多种抗生素耐药.15株qnr基因阳性的菌株中7株质粒接合传递试验成功,临床株对喹诺酮类和氨基糖苷类的耐药性部分传递给了受体株.结论 qnr基因在温州地区环丙沙星耐药的肠杆菌科细菌临床株中较少见,而aac(6')-Ⅰ b-cr基因存在较普遍.