16S rRNA甲基化酶在氨基糖苷类抗生素耐药革兰阴性菌中的分布

目的了解6种编码16SrRNA甲基化酶的基因在氨基糖苷类抗生素耐药革兰阴性菌中的流行情况。方法收集本院2007年10～12月分离的211株阿米卡星和庆大霉素耐药革兰阴性菌，采用PCR检测其中6种甲基化酶基因（armA、rmtA、rmtB、rmtC、rmtD和npmA）的分布。对16SrRNA甲基化酶基因阳性的菌株，用ERIC-PCR进行同源性分析。结果211株阿米卡星和庆大霉素耐药革兰阴性菌中，91．5％（193／211）被检出16SrRNA甲基化酶基因，其中133株含armA（133／211，63．0％），60株含rmtB（60／211，28．4%）。阿米卡星MIC≥512mg／L、庆大霉素MIC≥128mg／L的104株肠杆菌科细菌中，甲基化酶基因检出达100％，且armA和rmtB的检出相仿（分别为49与55株）。阿米卡星MIC≥512mg／L、庆大霉素MIC≥128mg／L的94株铜绿假单胞菌和鲍曼不动杆菌中，甲基化酶检出94．7％（89株），以armA（84株）为主。未检测到rmtA，rmtC，rmtD和npmA基因。ERIC-PCR结果显示该类基因并非单克隆传播。结论几乎所有临床分离的阿米卡星MIC〉512mg／L的革兰阴性菌中都能检出armA或rmtB基因。     

革兰阴性杆菌16S rRNA甲基化酶基因检测及作用研究

目的分析上海中医药大学附属普陀医院临床分离的革兰阴性杆菌中16S rRNA甲基化酶基因的流行情况及革兰阴性杆菌的氨基糖苷类耐药机制。方法收集临床分离的对阿米卡星和/或庆大霉素耐药的革兰阴性杆菌53株。采用聚合酶链反应（PCR）法检测16S rRNA甲基化酶基因：armA、rmtA、rmtB、rmtC、rmtD、npmA;PCR阳性产物测序分析。构建PET32-armA和PET32-rmtB的重组质粒并转化入宿主菌BL21中。纸片扩散法（K-B）检测临床分离16S rRNA甲基化酶基因阳性菌株和重组菌对5种氨基糖苷类药物的敏感性。结果 53株耐药菌中5株鲍曼不动杆菌、2株肺炎克雷伯和1株阴沟肠杆菌检出armA基因,2株大肠埃希菌检出rmtB基因。获得PET32-armA和PET32-rmtB的重组BL21菌株。PET32-armA和PET32-rmtB的重组菌均获得氨基糖苷类抗菌药物耐药性。结论本院临床样本检测到16S rRNA甲基化酶基因armA和rmtB阳性菌株,armA基因存在于鲍曼不动杆菌、肺炎克雷伯菌和阴沟肠杆菌中;rmtB基因位于大肠埃希菌中。将armA和rmtB基因转入非耐药的宿主菌中可以诱导其对氨基糖苷类抗菌药物的耐药。     

肠杆菌科细菌对氨基糖苷类的耐药性及16S rRNA甲基化酶基因的检测研究

目的了解氨基糖苷类耐药肠杆菌科细菌的分布、耐药情况,及16S rRNA甲基化酶基因型的分布,为临床用药提供参考依据。方法收集宁夏医科大学总医院2017年临床分离的非重复肠杆菌科细菌142株,细菌鉴定采用VITEK-2Compact系统,药敏试验采用肉汤微量稀释法,PCR扩增16S rRNA甲基化酶基因(armA、rmtA、rmtB、rmtC、rmtD、rmtE、rmtF、rmtG、rmtH、npmA)。结果 142株肠杆菌科细菌中72株对氨基糖苷类耐药。这72株菌对头孢菌素类、氟喹诺酮类、氨曲南的耐药率均≥77.1%,对酶抑制剂复合制剂头孢哌酮-舒巴坦、哌拉西林-他唑巴坦的耐药率≥51.4%,对头孢他啶-阿维巴坦、替加环素的耐药率10%,对碳青霉烯类耐药率≤40.0%。氨基糖苷类敏感株对多数抗菌药物的耐药率低于氨基糖苷类耐药株。氨基糖苷类耐药株中有71株检出16S rRNA甲基化酶基因,总阳性率为50.0%(71/142),在氨基糖苷类耐药株中的阳性率为98.6%(71/72)。71株中rmtB 54株,占76.1%;armA 14株,占19.7%;rmtA 2株,占2.8%;rmtB+armA 1株,占1.4%。未检出rmtC、rmtD、rmtE、rmtF、rmtG、rmtH和npmA基因。结论 rmtB和armA 16S rRNA甲基化酶是该院临床分离肠杆菌科细菌对氨基糖苷类耐药的主要机制。     

阴沟肠杆菌16SrRNA甲基化酶基因分布

目的：了解湖南邵阳地区耐氨基糖苷类抗菌药物的阴沟肠杆菌中16S rRNA甲基化酶基因分布特点及其与氨基糖苷类抗菌药物耐药性的关系。方法收集2012年8月至2014年5月邵阳地区新宁县人民医院、武岗市人民医院、邵阳县人民医院和邵阳医学高等专科学校附属医院临床样本中分离的241株阴沟肠杆菌,采用API20E进行菌种鉴定,同时用纸片扩散法进行体外药物敏感性试验。采用聚合酶链反应（ PCR）进行armA、npmA、rmtA、rmtB、rmtC和rmtD基因检测,分析耐药基因与耐药表型的关系。结果241株阴沟肠杆菌中200株对阿米卡星、庆大霉素、妥布霉素和奈替米星4种氨基糖苷类抗菌药物耐药,其耐药率分别为41．9％、68．5％、70．1％和63．5％。基因检测结果提示,241株阴沟肠杆菌检出2种16S rRNA甲基化酶基因,分别为armA（96株,39．8％）和rmtB（17株,7．1％）,未检出npmA、rmtA、rmtC和rmtD基因。结论16S rRNA甲基化酶与氨基糖苷类抗菌药物的耐药性有相关性。不同地区分离的对氨基糖苷类药物耐药的阴沟肠杆菌菌株携带16S rRNA甲基化酶的基因型有一定差异,湖南邵阳地区阴沟肠杆菌以携带armA基因为主。     

多重耐药鲍曼不动杆菌中16SrRNA甲基化酶基因的检测及耐药分析

目的了解医院分离的多重耐药鲍曼不动杆菌16SrRNA甲基化酶基因分布情况,为临床合理应用抗菌药物提供依据。方法采用Phoenix100微生物全自动鉴定系统进行菌株鉴定及药敏试验;采用PCR方法检测armA、rmtA、rmtB、rmtC、rmtD基因。结果 46株鲍曼不动杆菌中armA基因阳性36株,阳性率78.3%,未检出rmtA、rmtB、rmtC、rmtD基因。药敏试验结果显示医院分离的多重耐药鲍曼不动杆菌对多黏菌素全部敏感,对四环素、阿米卡星、庆大霉素、妥布霉素、甲氧苄啶-磺胺甲唑耐药率分别为13.0%、80.4%、91.3%、95.7%、95.7%,对其他测试药物耐药率100%。结论医院分离鲍曼不动杆菌对氨基糖苷类抗菌药物耐药性已非常严重,携带armA基因是导致氨基糖苷类耐药的原因之一,延缓鲍曼不动杆菌多重耐药性已刻不容缓。     

阿米卡星耐药鲍曼不动杆菌16S rRNA甲基化酶基因的研究

目的了解阿米卡星耐药鲍曼不动杆菌中16S rRNA甲基化酶基因的分布情况。方法收集2010年1月—2012年4月临床标本中分离的阿米卡星耐药鲍曼不动杆菌54株。5种16 S rRNA甲基化酶基因(armA、rmtA、rmtB、rmtC和rmtD)的检测采用聚合酶链反应(PCR)方法,PCR产物采用琼脂糖凝胶电泳分析并将阳性扩增产物进行测序。抗菌药物的药敏试验采用纸片扩散法进行,WHONET5.5软件进行统计分析。结果 54株阿米卡星耐药鲍曼不动杆菌中40株检出16S rRNA甲基化酶基因armA,检出率为74.1%,未检出rmtA、rmtB、rmtC及rmtD基因。54株阿米卡星耐药鲍曼不动杆菌对米诺环素、亚胺培南和美罗培南耐药率分别为38.9%、63.0%和64.8%,对其余14种抗菌药物耐药率均在85.0%以上。结论阿米卡星耐药鲍曼不动杆菌主要携带armA型16S rRNA甲基化酶耐药基因,除米诺环素对该菌有较好的抗菌活性外,该菌对其他16种抗菌药物耐药严重。     

广泛耐药铜绿假单胞菌甲基化酶基因的检测和基因周边结构分析

目的了解16S rRNA甲基化酶基因在广泛耐药(XDR)铜绿假单胞菌临床株中的分布及此类耐药基因周边结构。方法收集XDR铜绿假单胞菌59株,琼脂稀释法测定MIC,PCR方法检测16S rRNA甲基化酶基因(armA,rmt A,rmtB,rmtC,rmtD,rmtE,npmA),ERIC-PCR方法进行同源性分析,并对检出的16S rRNA甲基化酶基因armA和rmtB进行周边序列分析。结果 59株XDR铜绿假单胞菌临床分离株中,16S rRNA甲基化酶基因总检出率62.7%(37/59),rmtB的检出率略高于armA,未检出其他甲基化酶基因。根据ERIC-PCR结果受试临床株可分为19个型别。17株检出armA基因菌株分布在3个克隆,其中15株(88.2%)集中在一个克隆(克隆D);而rmtB基因散布于9个克隆。基因周边序列分析显示,armA基因位于一个含多种转座酶的移动元件上,其与大肠埃希菌和鲍曼不动杆菌携带的armA阳性质粒序列一致性达99%;rmtB基因也位于一个含转座酶的移动元件上,其与大肠埃希菌和肺炎克雷伯菌携带的rmtB质粒序列高度一致。结论 16S rRNA甲基化酶基因在XDR铜绿假单胞菌分离株中分布广泛,均在对庆大霉素高度耐药的菌株中检出。armA在铜绿假单胞菌中存在克隆传播。     

大肠埃希菌16S rRNA甲基化酶基因的接合传递及其与整合子的相关性

目的 对临床分离的多重耐药（MDR）大肠埃希菌株的16S rRNA甲基化酶基因特征与接合传递效率进行研究,探讨其与整合子的相关性。 方法 136株MDR大肠埃希菌经PCR筛检16S rRNA甲基化酶基因armA、rmtA、rmtB、rmtC、rmtD;对阳性菌株作整合酶基因intI1、intI2和intI3检测,并扩增Ⅰ类整合子可变区插入片段,对扩增产物进行测序与鉴定所含耐药基因盒;以阳性菌株为供体菌,耐叠氮化钠大肠埃希菌J53为受体菌进行接合试验,并结合质粒图谱对16S rRNA甲基化酶基因进行初步定位。 结果 在136株多重耐药大肠埃希菌中,共检出16S rRNA甲基化酶阳性菌12株（8.8%）,其中,armA阳性3株（2.2%）,rmtB阳性10株（7.4%）,未检出rmtA、rmtC、rmtD基因。阳性菌株均只含Ⅰ类整合子,对其可变区扩增片段（1 000～2 300 bp）的测序结果显示,该区域含有多种耐药基因盒,但不含16S rRNA甲基化酶基因。接合试验与质粒图谱结果初步表明armA和rmtB编码基因位于约23 000 bp的质粒上,接合试验的耐药质粒传递率高达83.3%(10/12)。 结论 在MDR大肠埃希菌中,armA和rmtB编码基因位于约23 000 bp质粒上,其中,rmtB为优势基因,接合试验和质粒图谱证明该类耐药质粒很容易在同种菌间传播。Ⅰ类整合子与16S rRNA甲基化酶基因虽然存在于同一菌体内和/或同处于一个质粒上,但整合子基因盒对该类基因的捕获率很低或根本不捕获。     

耐碳青霉烯类肺炎克雷伯菌临床分离株中喹诺酮类及16SrRNA甲基化酶基因的检测

目的了解临床分离株中耐碳青霉烯肺炎克雷伯菌(CRKP)的氟喹诺酮类耐药基因及16SrRNA甲基化酶基因存在情况和药敏特点。方法收集临床标本中分离的6株CRKP,采用VITEK 2compact全自动微生物鉴定和药敏系统鉴定细菌及药敏试验,采用聚合酶链反应(PCR)扩增氟喹诺酮类耐药基因和16SrRNA甲基化酶基因。结果 6株CRKP临床分离株呈现多药耐药特点,对环丙沙星和左氧氟沙星的耐药率分别是83.3%和83.3%,对庆大霉素、阿米卡星和妥布霉素的耐药率分别是66.7%,50%和66.7%。检出喹诺酮类耐药相关基因qnrB,qnrS和qnrD,基因阳性率分别为50%,50%和33.3%,未检出qnrA,qnrC和qepA基因。检出16SrRNA甲基化酶耐药相关基因armA,基因阳性率为50%,未检出rmtA,rmtB,rmtC和npmA基因。结论 6株CRKP对喹诺酮类和氨基糖类抗生素耐药严重,其耐药性与喹诺酮类耐药基因及16SrRNA甲基化酶基因高度相关,其耐药基因主要型别分别是qnrB,qnrS,qnrD和armA。     

氨基糖苷类耐药的肠杆菌科细菌16S rRNA甲基化酶基因研究

目的探讨临床分离的对氨基糖苷类耐药的肠杆菌科细菌产16S rRNA甲基化酶状况,分析其分子流行趋势及其耐药性形成和传播的机制。方法采用纸片扩散法筛选庆大霉素和/或阿米卡星耐药的肠杆菌科细菌;采用聚合酶链反应(PCR)扩增16S rRNA甲基化酶基因、氨基糖苷修饰酶基因、β-内酰胺酶基因;采用质粒接合试验验证16S rRNA甲基化酶的转移性;应用脉冲场凝胶电泳(PFGE)对16S rRNA甲基化酶基因阳性菌株进行分型。结果 201株对庆大霉素和/或阿米卡星耐药的肠杆菌科细菌中共检出38株16S rRNA甲基化酶阳性株(armA基因16株,rmtB基因22株)。其中30株可通过接合试验将耐药质粒转移至受体菌。blaCTX-M-14、blaTEM-1和blaSHV-12可连同armA或rmtB分别转移到11、20和7个接合子中。肺炎克雷伯菌、大肠埃希菌和阴沟肠杆菌分别被PFGE分为4、21和1个型别。结论本研究分离的肠杆菌科细菌16S rRNA甲基化酶以armA和rmtB为主要流行型别,且后者分离率较高。该甲基化酶可导致氨基糖苷类高水平耐药,而且酶编码基因位于质粒上,具有转移性,β-内酰胺酶基因和氟喹诺酮耐药决定因子可随之一同转移。     

Emergence of ArmA and RmtB aminoglycoside resistance 16S rRNA methylases in Belgium

OBJECTIVES: 16S rRNA methylase-mediated high-level resistance to aminoglycosides has been reported recently in clinical isolates of Gram-negative bacilli only from a limited number of countries. This study was conducted to investigate the occurrence of this type of resistance in clinical isolates of Enterobacteriaceae from two Belgian hospitals and the characteristics of the strains. METHODS: We screened for high-level gentamicin, tobramycin and amikacin resistance in clinical isolates of Enterobacteriaceae consecutively collected between 2000 and 2005 at two laboratories by PCR for the armA, rmtA and rmtB 16S rRNA methylase genes. The beta-lactamase presence in the strains was also determined by phenotypic and genotypic methods. RESULTS: Overall armA genes were detected in 18 Klebsiella pneumoniae, Escherichia coli, Enterobacter aerogenes, Enterobacter cloacae and Citrobacter amalonaticus whereas rmtB was detected in a single E. coli isolate. The rmtA gene was not found. All 16S rRNA methylase-bearing strains produced extended-spectrum beta-lactamases (ESBLs), predominantly type CTX-M-3, as well as various types of beta-lactamases. In the majority of the strains, the armA gene was carried by conjugative plasmids of the IncL/M incompatibility group whereas rmtB was borne by an IncFI plasmid. CONCLUSIONS: This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Belgium. The rapid spread of multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases raises clinical concern and may become a major therapeutic threat in the future.     

Detection of methyltransferases conferring high-level resistance to aminoglycosides in enterobacteriaceae from Europe, North America, and Latin America

The alteration of ribosomal targets by recently described 16S rRNA methyltransferases confers resistance to most aminoglycosides, including arbekacin. Enterobacteriaceae and nonfermentative bacilli acquired through global surveillance programs were screened for the presence of these enzymes on the basis of phenotypes that were resistant to nine tested aminoglycosides. Subsequent molecular studies determined that 20 of 21 (95.2%) methyltransferase-positive isolates consisted of novel species records or geographic occurrences (North America [armA and rmtB], Latin America [rmtD], and Europe [armA]; rmtA, rmtC, and npmA were not detected). The global emergence of high-level aminoglycoside resistance has become a rapidly changing event requiring careful monitoring.     

Emergence of RmtB methylase-producing Escherichia coli and Enterobacter cloacae isolates from pigs in China

OBJECTIVES: To investigate the occurrence of 16S rRNA methylases conferring high-level resistance to aminoglycosides in Enterobacteriaceae isolated from two pig farms in China. METHODS: Enterobacteriaceae isolated from 151 pig rectal swab samples and 9 environmental samples were screened for the presence of the rmtA, rmtB, armA and rmtC genes by PCR and sequencing. Conjugation experiments were carried out to study the transferability of the 16S rRNA methylase genes. All isolates and their transconjugants were tested for susceptibility to antimicrobial agents. The clonal relatedness of RmtB-producing Escherichia coli was assessed by PFGE with XbaI. RESULTS: Of 152 Enterobacteriaceae isolates recovered from pigs, 49 (32%) were positive for the rmtB gene, including 48 E. coli and a single isolate of Enterobacter cloacae. Of the nine Enterobacteriaceae isolates from environmental samples, no 16S rRNA methylase gene was identified. The 49 rmtB-positive isolates showed resistance to ampicillin, tetracycline and trimethoprim and also carried a bla(TEM) gene. Transfer of the rmtB and bla(TEM) genes by conjugation experiments of all 49 isolates was successful, suggesting that the rmtB-containing plasmids in the E. coli and E. cloacae isolates were self-transmissible. Conjugative transfer frequencies varied from 2.2 x 10(-10) to 1.3 x 10(-6) transconjugants per recipient. The transfer of non-aminoglycoside antimicrobial resistance traits was also observed in most cases. Forty-four rmtB-positive E. coli showed 30 different PFGE types. CONCLUSIONS: The rmtB gene was detected on conjugative plasmids of porcine E. coli and E. cloacae isolates. Both horizontal gene transfer and clonal spread were responsible for the dissemination of the rmtB gene. The emergence of 16S rRNA methylases in Enterobacteriaceae isolates is described for the first time in China. This is also the first report of rmtB-positive Enterobacteriaceae among healthy food-producing animals.     

质粒介导16S rRNA甲基化酶肺炎克雷伯菌临床分离株的检测及分子流行病学研究

目的 调查165 rRNA甲基化酶在肺炎克雷伯菌临床分离株中的流行情况.方法 收集我院2006年1月至2007年9月从临床标本中分离的肺炎克雷伯菌337株,所有菌株均为非重复株.菌种鉴定采用全自动微生物分析仪,庆大霉素、阿米卡星和妥布霉素的药敏试验采用琼脂稀释法.超广谱B内酰胺酶(ESBLs)检测采用美国临床和实验窒标准协会(CLSI)规定的纸片确证法.使用PCR检测16S rRNA甲基化酶基因、整合酶基因和ESBL基因.接合试验检测质粒的可转移性;脉冲场电泳分析菌株的同源性.结果 337株肺炎克雷伯菌对庆大霉素、妥布霉素和阿米卡星的耐药率分别为19.0%(64/337)、8.3%(28/337)和16.3%(55/337).21株16S rRNA甲基化酶基因阳性,阳性率为6.2%(21/337),其中13株rmtB阳性、3株armA阳性、5株rmtB和atmA同时阳性.所有16S rRNA甲基化酶基因阳性株对庆大霉素、妥布霉素和阿米卡星同时耐药且都为高度耐药(MICs≥256μL),21株甲基化酶基因阳性株有19株产ESBLs,ESBL基因主要为CTX-M-14-like、CTX-M-15-like和SHV-12-like.21株均为Ⅰ类整合酶基因阳性.13株通过接合试验把质粒传递给受体菌E. coliJ53.所有接合子Ⅰ类整合酶基因阳性、blaTEM-1基因阳性、产ESBLs及对庆大霉素、妥布霉素、阿米卡星和复方磺胺甲噁唑耐药,对其他抗菌药物敏感.接合子ESBL基因型与供菌一致.21株16S rRNA甲基化酶基因阳性株经脉冲场凝胶电泳(PFGE)分成14个基因型,主要为A型和Ⅰ型.结论 armA和rmtB型16S rRNA甲基化酶基因已经在肺炎克雷伯菌中播散,既可通过克隆株播散也可通过接合性质粒在不同菌株间播散.     

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.     

Plasmid-mediated 16S rRNA methylases conferring high-level aminoglycoside resistance in Escherichia coli and Klebsiella pneumoniae isolates from two Taiwanese hospitals

OBJECTIVES: This study was conducted to investigate the occurrence of 16S rRNA methylases that confer high-level aminoglycoside resistance in Klebsiella pneumoniae and Escherichia coli isolates from two Taiwanese hospitals and the characteristics of these isolates. METHODS: A total of 1624 K. pneumoniae and 2559 E. coli isolates consecutively collected over an 18 month period from a university hospital and seven E. coli and eight K. pneumoniae isolates that were resistant to amikacin from a district hospital were analysed. Two 16S rRNA methylase genes, armA and rmtB, were detected by PCR-based assays. beta-Lactamase characteristics were determined by phenotypic and genotypic methods. RESULTS: Overall, 28 armA-positive and seven rmtB-positive isolates were identified, and extended-spectrum beta-lactamases (ESBLs) were detected in 33 (94.3%) isolates. The prevalence rates of armA and rmtB at the university hospital were 0.9% (n=15) and 0.3% (n=5) in K. pneumoniae and 0.4% (n=10) and 0.04% (n=1) in E. coli. CTX-M-3, CTX-M-14, SHV-5-like ESBLs, and CMY-2 were detected alone or in combination in 21, 6, 11, and 2, respectively, of the 28 armA-positive isolates. CTX-M-14 was detected in six of the seven rmtB-positive isolates. Fingerprinting of conjugative plasmids revealed the dissemination of closely related plasmids containing both armA and bla(CTX-M-3). PFGE suggests that armA and rmtB spread by both horizontal transfer and clonal spread. CONCLUSIONS: This is the first report of the emergence of 16S rRNA methylases in Enterobacteriaceae in Taiwan. The spread of the multidrug-resistant isolates producing both ESBLs and 16S rRNA methylases may become a clinical problem.     

Dissemination of 16S rRNA methylase-mediated highly amikacin-resistant isolates of Klebsiella pneumoniae and Acinetobacter baumannii in Korea

Novel 16S rRNA methylase-mediated high-level resistance to amikacin and arbekacin has been reported recently in clinical isolates of Gram-negative bacilli only from several countries. We tested amikacin- or arbekacin-nonsusceptible Gram-negative bacilli isolated in 2003 and 2005 at a tertiary-care hospital in Korea by polymerase chain reaction to detect 16S rRNA methylase genes. armA alleles were detected in 14 isolates of Klebsiella pneumoniae, 10 other species of Enterobacteriaceae, and 16 Acinetobacter baumannii, whereas the rmtB allele was detected in 1 K. pneumoniae isolate. The resistance 1st detected in 2003 persisted in 2005. 16S rRNA methylase-producing isolates were highly resistant to arbekacin and amikacin, and were mostly coresistant to levofloxacin. Most K. pneumoniae isolates also produced extended-spectrum beta-lactamases and plasmid-mediated AmpC beta-lactamases, and most A. baumannii isolates were nonsusceptible to carbapenems.     

鲍曼不动杆菌对氨基糖苷类药物耐药及其携带基因的探讨

目的探讨鲍曼不动杆菌对氨基糖苷类药物耐药情况和耐药表型及其携带基因的关系。方法收集48株鲍曼不动杆菌,用K-B法和琼脂稀释法检测其对阿米卡星的敏感性,PCR法扩增aac(6′)Ⅰ基因以及3种16SrRNA甲基化酶基因(armA、rmtB及rmtC基因)。结果 72.9%(35/48)菌株对阿米卡星表现为双圈耐药,其中100.0%菌株检出armA基因,未检出rmtB、rmtC基因,77.1%(27/35)菌株检出aac(6′)Ⅰ基因;10.4%(5/48)菌株对阿米卡星普通耐药,均未检出16SrRNA甲基化酶基因,其中80.0%(4/5)菌株检出aac(6′)Ⅰ基因;16.7%(8/48)菌株对阿米卡星敏感,未检出相关耐药基因。结论鲍曼不动杆菌对阿米卡星的耐药情况非常严重;双圈耐药现象与armA基因诱导型表达有关。