耐亚胺培南鲍曼不动杆菌医院内感染流行的分子机制研究

目的研究耐亚胺培南鲍曼不动杆菌的耐药谱特征及其医院内感染流行和耐药性产生的分子机制,为临床防治提供依据.方法4株耐亚胺培南鲍曼不动杆菌分离自2002年10月至2003年1月外科重症监护病房的感染患者,采用纸片扩散法及E-test进行药物敏感性检测及MIC值测定,肠杆菌科基因组内重复一致序列聚集合酶链反应(ERIC-PCR)进行克隆株的DNA分型,耐药质粒转移及消除试验、等电聚焦电泳、PCR扩增β-内酰胺酶基因及其克隆测序以识别其耐药基因和进行质粒定位.结果4株菌除对头孢哌酮/舒巴坦复合制剂的MIC值较低外,对头孢菌素类、氨基糖甙类和氟喹喏酮类等抗生素均显示出了较高水平的多重耐药性;DNA分型证实为同一克隆株;产OXA-23型碳青霉烯酶和PER-1型超广谱β-内酰胺酶(ESBLs);OXA-23定位在质粒上,PER-1定位在染色体上.结论本组耐亚胺培南鲍曼不动杆菌为多重耐药株,同一克隆株在不同感染个体间的相互传播导致了本次医院内感染的流行,产OXA-23和PER-1型β-内酰胺酶是其耐药性产生的重要原因.     

鲍曼不动杆菌对碳青霉烯类抗生素的耐药性分析

目的了解鲍曼不动杆菌的耐药情况,并检测耐碳青霉烯类鲍曼不动杆菌的耐药基因,为指导临床合理用药、控制院内感染提供依据。方法利用K-B法检测45株鲍曼不动杆菌临床分离株的耐药情况,通过改良Hodge试验、Carba NP试验和EDTA协同试验对多重耐药鲍曼不动杆菌的碳青霉烯酶进行表型检测,并采用PCR技术检测鲍曼不动杆菌携带OXA-23和NDM-1型耐药基因的情况。结果 45株鲍曼不动杆菌临床分离株中共筛出42株多重耐药菌株;利用改良Hodge试验和Carba NP试验检出36株碳青霉烯酶阳性菌株;采用PCR扩增出OXA-23,未扩增出NDM-1。结论鲍曼不动杆菌耐药情况严重,且耐药基因OXA-23携带率高,治疗时应根据药敏试验结果合理用药。     

The role of bla(OXA-like carbapenemase) and their insertion sequences (ISS) in the induction of resistance against carbapenem antibiotics among Acinetobacter baumannii isolates in Tehran hospitals

This study aimed to evaluate the occurrence and dissemination of bla(OXA-like) carbapenemase genes and their insertion sequences among Acinetobacter baumannii isolates, taken from different hospitals in Tehran city and also their roles in the induction of resistance to carbapenem drugs. A total number of 100 non duplicate Acinetobacter baumannii with different origins, were isolated from patients with proved nosocomial infections at eight university hospital in Tehran city. Antimicrobial susceptibility of these strains was done by E-test against 7 antimicrobial agents according to CLSI guideline. PCR of bla(OXA-51-like), bla(OXA-23-like), bla(OXA-24-like), bla(OXA-58-like), IS(ABA-1), IS(1133) was carried out by specialized primers and then these strains were typed by REP-fingerprinting. Colistin, imipenem and meropenem were the most sensitive antibiotics against Acinetobacter baumannii isolates with 96%, 51% and 51% sensitivity respectively. All the isolates had a bla(OXA-51-like) intrinsic to these species. The rates of bla(OXA-23), 23 and 58-like were 38%, 32% and 1% respectively. Coexistence of bla(OXA-51/23/24-like) was observed among 16% of these isolates. All bla(OXA-23-like) carbapenemase genes had only one IS(ABA1). REP fingerprinting showed 5 genotypes among carbapenem resistant isolates, 16 of them being genotype A. This study emphasized on the major role of bla(OXA-like) carbapenemase, particularly bla(OXA-23-like) carbapenemase and their IS(ABA1), in the dissemination of carbapenem resistant Acinetobacter baumannii. This study confirmed a presumptive role of IS element neighboring the carbapenemase gene in the elevation of resistance to carbapenem drug among Acinetobacter baumannii isolates for the first time in Iran.     

Emergence and spread of carbapenem-resistant Acinetobacter baumannii in a tertiary care hospital in Turkey

An intensive care unit (ICU)-based OXA-23-producing multiple-drug resistant Acinetobacter baumannii (MDRAB) outbreak was detected between October 2005 and October 2006. A total of 47 patients were infected/colonized with the outbreak strain. Clinical data were available from 37 patients. The all-cause mortality rate among the patients exposed to the epidemic strain was 35% (13/37). The outbreak strain and the resistance determinants were characterized both by microbiological methods and by molecular techniques. Cloning and sequencing experiments identified ISAbaI-associated bla(oxa-23) on the chromosome. Screening of imipenem-resistant Acinetobacter isolated from the ICU during the outbreak period with PCR identified 97 isolates as positive for the ISAbaI-bla(oxa-23) structure. Pulsed-field gel electrophoresis and plasmid analyses with selected nonrepetitive isolates revealed the clonality. Disk diffusion on cloxacillin-supplemented agar media and the real-time PCR experiments showed that outbreak isolates are overexpressing the ampC enzyme. This study highlights the occurrence of OXA-23-producing and ampC-overexpressing MDRAB in ICUs.     

福州地区碳青霉烯类耐药鲍曼不动杆菌碳青霉烯酶基因型研究

目的探讨福州地区碳青霉烯类耐药鲍曼不动杆菌(CRAB)碳青霉烯酶基因型的流行情况。方法收集多家医院临床标本中分离得到的107株CRAB。应用K-B纸片扩散法进行药物敏感试验。采用PCR法检测7种碳青霉烯酶基因,包括OXA-23、OXA-24、OXA-51、OXA-58、IMP-1、IMP-4和VIM-2。结果 107株CRAB对除多粘菌素B、米诺环素外的其他所有常见的抗生素均为耐药。碳青霉烯酶基因OXA-51、OXA-23的检出率分别为100.0%(107/107)和87.9%(94/107)。其他OXA-24、OXA-58、IMP-1、IMP-4和VIM-2基因均未检出。结论福州地区临床分离的CRAB耐药现象严重;表达OXA-23基因是CRAB对碳青霉烯类药物耐药的重要机制之一。     

危重病房耐碳青霉烯酶鲍曼不动杆菌同源性研究

目的探讨杭州市第一医院危重病房耐碳青霉烯酶鲍曼不动杆菌之间的同源性,进行分子流行病学调查,旨在为制定预防和控制其院内感染的措施提供依据。方法收集该院危重病房2005年1月至12月分离到的34株亚胺培南耐药鲍曼不动杆菌。采用全自动微生物分析系统VITEK-AMS60对34株耐碳青霉烯酶鲍曼不动杆菌进行鉴定及药敏;用琼脂稀释法和E-test法测定14种抗菌药物的最低抑菌浓度(MIC),脉冲场凝胶电泳(PF-GE)分析其耐药株的同源性,对碳青霉烯类基因OXA-23型、OXA-24型、IMP型、VIM型基因进行PCR扩增及序列分析。结果PFGE发现34株鲍曼不动杆菌菌株为同一耐药克隆株,在危重病房呈爆发流行。所有对亚胺培南耐药鲍曼不动杆菌明确产OXA-23型碳青霉烯酶,未检出OXA-24、IMP、VIM基因型。34株菌株质粒提取未成功。结论该院同一个耐药克隆株在危重病房不同患者身上流行,可能与行气管插管、呼吸机、氧气湿化瓶、护士手操作有关。     

Distribution of blaOXA genes among carbapenem-resistant Acinetobacter baumannii nosocomial strains in Poland

Acinetobacter baumannii is an important nosocomial pathogen occurring particularly in intensive care (ICU) as well as burn therapy units (BTU). A. baumannii strains have emerged as resistant to almost all antimicrobial agents, including carbapenems. b-lactamase-mediated resistance is the most common mechanism for carbapenem resistance in this species. Carbapenem-hydrolysing class D b-lactamases - OXA are widespread among A. baumannii strains. It is suggested that ISAba1 plays an important role in drug resistance. The aims of the study were detection of OXA encoding genes and presence of ISAba1. The study included the total of 104 isolates of carbapenem-resistant A. baumannii, obtained from patients hospitalized in ICU and BTU of Specialized Hospital in Krakow. Multiplex PCR was applied for detection of selected OXA carbapenemases encoding genes. PCR analysis showed the presence of bla OXA-51-like gene and ISAba1 in all isolates. 46 strains carried bla OXA-51-like and bla OXA-23-like genes while 48 bla OXA-51-like and bla OXA-40-like genes. 3 isolates carried: bla OXA-51-like , bla OXA-23-like and bla OXA-40-like genes. 7 strains encoded an OXA-51-like carbapenemase but were negative for enzymes belonging to the other families tested. Comparative analysis of ICU and BTU isolates revealed the dominance of: bla OXA-51-like and bla OXA-40-like among ICU while bla OXA-51-like and bla OXA-23-like in BTU.     

鲍曼不动杆菌对碳青霉烯类抗生素的耐药性及其基因的分析

目的研究23株鲍曼不动杆菌对碳青霉烯类抗生素的耐药情况及对耐药基因分析,为临床用药提供依据。方法用珠海迪尔DL-96鉴定系统进行细菌鉴定及K-B法进行药敏试验,用碳青霉烯酶4种基因的特异性引物对其进行聚合酶链反应(PCR)扩增和基因型分析,并通过网上GenBank进行比对以确定编码酶基因的类型。结果 23株鲍曼不动杆菌对哌拉西林/他唑巴坦、左旋氧氟沙星、丁胺卡那霉素、多黏菌素B的耐药率分别为80%、45%、30%、10%,对其他抗生素的耐药率均在90%以上。携带D类碳青霉烯酶OXA-23基因有18株(78%),携带OXA-51基因有15株(65%),OXA-24、OXA-58基因引物PCR扩增为阴性,随机各抽取3株OXA-23基因阳性株进行测序后通过在网上GenBank比对与OXA-23标准株99%同源,OXA-51基因阳性株与OXA-51标准株98%同源。结论耐碳青霉烯类抗生素的鲍曼不动杆菌对多黏菌素的耐药率最低,其次是丁胺卡那霉素,其中以携带OXA-23型碳青霉烯酶基因为主,应引起临床高度关注,防止在院内广泛传播。     

鲍曼不动杆菌耐药性监测与碳青霉烯酶基因型研究

目的：对鲍曼不动杆菌耐药性及碳青霉烯酶基因型进行研究,以指导临床合理应用抗生素。方法：收集青岛市海慈医疗集团2009年6月至2010年6月从临床分离的鲍曼不动杆菌60株,用琼脂稀释法测定最低抑菌浓度（M IC）,改良Hodge试验检测碳青霉烯酶,用PCR法检测OXA-23,OXA-24,OXA-58基因,并对PCR产物进行测序。结果：①鲍曼不动杆菌检出率前两位是ICU病房和呼吸科病房,分别占32.3%和27.4%,多重耐药鲍曼不杆菌阳性率最高的是ICU,为70.6%（12/17）,其次为呼吸科病房,为35.0%（7/20）,哌拉西林、哌拉西林/他唑巴坦、头孢曲松、头孢他啶、头孢吡肟、亚胺培南、美罗培南、庆大霉索、阿米卡星、环丙沙星、左氧氟沙星、加替沙星、头孢哌酮/舒巴坦、氨曲南耐药率分别为92.3%、55.4%、88.6%、86.3%、80.3%、30.0%、35.0%、76.6%、79.6%、75.1%、87.1%、48.3%、42.0%和79.6%.②在21株耐碳青霉烯类鲍曼不动杆菌,有14株碳青霉烯酶表型阳性,检出率为66.7%,有18株PCR扩增出OXA-23基因,检出率85.7%,全部菌株blaOXA-24及blaOXA-58PCR扩增均为阴性,PCR产物测序表明与鲍曼不动杆菌（AY795964.1）blaOXA-23基因序列100%同源。结论：鲍曼不动杆菌多重耐药性严重;表型和基因型检测证实本院临床分离鲍曼不动杆菌对碳青霉烯类耐药机制主要是产OXA-23型酶。     

Prevalence of OXA-type carbapenemase genes and genetic heterogeneity in clinical isolates of Acinetobacter spp. from Mangalore, India

The prevalence of OXA-type carbapenemase genes, ISAba1 insertion sequence, carbapenem resistance, biofilm forming ability and genetic heterogeneity in clinical isolates of Acinetobacter spp. from hospitals in Mangalore, South India was studied. Based on the presence of the bla(OXA-51) -like gene, the 62 isolates of Acinetobacter spp. were identified as 48 A. baumannii and 14 other Acinetobacter spp. The prevalence of bla(OXA-23) -like, bla(OXA-24) -like and bla(OXA-58) -like genes in A. baumannii was 47.9%, 22.9% and 4.2%, while in other Acinetobacter spp. it was 28.5%, 64.3% and 35.7% respectively. Several A. baumannii isolates (16/48) harbored the insertion sequence ISAba1 in the upstream region of the bla(OXA-23) -like gene. Resistance to meropenem was seen in 39.6% and 14.2% of A. baumannii and other Acinetobacter spp. isolates, respectively. The ability to form biofilm was observed to be higher among A. baumannii in comparison to other Acinetobacter spp. The present study shows that bla(OXA-23) -like genes are more common in A. baumannii,whereas bla(OXA-24) -like genes are common to other Acinetobacter spp. The study revealed genetic heterogeneity among the isolates, indicating multiple sources in the hospitals.     

29株耐亚胺培南和/或美罗培南鲍曼不动杆菌产碳青霉烯酶基因型检测

目的 了解临床分离耐亚胺培南和/或耐美罗培南鲍曼不动杆菌中产碳青霉烯酶的基因型别.方法 采用聚合酶链反应扩增IMP、VIM、OXA型碳青霉烯酶基因并测序.结果 29株对碳青霉烯类耐药的鲍曼不动杆菌中,以产OXA-24型和IMP型酶菌株最多,二者均占51.7％ (15/29).产OXA-24+ IMP型5株、OXA-24+ OXA-51+IMP型4株、VIM型4株、OXA-24+ OXA-58+ IMP型、OXA-23+ OXA-24+ IMP型各2株,OXA-23+IMP型、OXA-51+OXA-24型、OXA-24型、IMP型各1株,8株细菌PCR检测结果为阴性.结论 耐亚胺培南和/或美罗培南鲍曼不动杆菌主要产OXA-24型和IMP型碳青霉烯酶,部分菌株可同时产2种或以上碳青霉烯酶.     

皖北地区耐碳青霉烯鲍曼不动杆菌产金属β-内酰胺酶检测

目的了解皖北地区ICU病房内耐碳青霉烯鲍曼不动杆菌产金属β-内酰胺酶（metallo-β-lactamase,MBL）情况。方法收集皖北地区3家教学医院ICU病房中不动杆菌,K-B纸片扩散法检测其对碳青霉烯类抗生素耐药情况;PCR法检测blaIMP、blaVIM等MBL基因。结果共收集35株耐亚胺培南、美罗培南非重复分离鲍曼不动杆菌菌株,其中9株（25.7%）金属酶初筛阳性;PCR检测5株（5/35,14.3%）产IMP型MBL,1株（1/35,2.9%）VIM型MBL。结论在本地区耐碳青霉烯鲍曼不动杆菌中首次发现IMP和VIM型金属酶,提示产金属酶机制参与本地区鲍曼不动杆菌对碳青霉烯耐药,值得进一步关注。     

Preparation, crystallization and preliminary X-ray crystallographic analysis of OXA-23, a carbapenemase conferring widespread antibiotic resistance

OXA-23, a class D carbapenemase that confers widespread antibiotic resistance hydrolyzes the beta-lactam rings of beta-lactam antibiotics, presenting an enormous challenge to infection control, particularly in the eradication of pathogenic bacteria such as Acinetobacter baumannii, one of six top-priority dangerous pathogens. Thus, the enzyme is a potential target for developing antimicrobial agents against pathogens producing carbapenemases. In this study, OXA-23 was purified and crystallized at 298 K and X-ray diffraction data from OXA-23 crystal were collected at 2.03 A resolution using synchrotron radiation. The crystal of OXA-23 belonged to space group P4(1) with unit cell parameters a = 82.47, b = 82.47 and c = 172.01 A. Analysis of the packing density showed that the asymmetric unit probably contained two molecules with a solvent content of 73.64%.     

Gram-negative bacteriae with resistance to carbapenems

Clinically-significant Gram-negative species remain mostly Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. Carbapenem molecules are often the last resort for treating infections due to multidrug resistant isolates. In Enterobacteriaceae, resistance to carbapenems may result from combined mechanisms of resistance associating b-lactamases with weak (if any) intrinsic carbapenemase activity and decreased outer membrane permeability, or from true carbapenemases. KPC-type enzymes (partially inhibited by clavulanic acid) have been identified mostly in Klebsiella pneumoniae, first in bacteria identified in the USA and then worldwide, and in many enterobacterial species. Carbapenem-hydrolyzing b-lactamases (CHBL) could be also metallo-b-lactamases (VIM, IMP, NDM-1, etc.) mostly in hospital-acquired K. pneumoniae. One of the latest reported CHBL in Enterobacteriaceae is OXA-48, identified mostly in Mediterranean countries. All these carbapenemase producers are difficult to detect in a clinical laboratory and may be the source of multidrug resistance leading to a therapeutic dead end. Whereas the main mechanism of resistance to imipenem in P. aeruginosa remains due to a modification of the outer membrane protein OprD, the landscape of CHBL in P. aeruginosa expanding worldwide is made of KPC, GES-related enzymes and metallo-b-lactamases (IMP, VIM, etc.). These enzymes are involved in multidrug resistance strains as a source of nosocomial outbreaks. In Acinetobacter baumannii, KPC and metallo-b-lactamases have been identified. However, the most frequent CHBL are oxacillinases (OXA-23, OXA-40, OXA-58, OXA-143) which are specific to that species. Novel carbapenemases are continuously being identified worldwide with exchange of the resistance genes between Enterobacteriaceae, P. aeruginosa and A. baumannii.     

First detection of OXA-24 carbapenemase-producing Acinetobacter baumannii isolates in Bulgaria

This report describes the first identification of OXA-24 carbapenemase-producing Acinetobacter baumannii isolates from Bulgaria. According to national surveillance data A. baumannii along with Pseudomonas aeruginosa are the most troublesome microorganisms in hospital environment with high rates of acquired carbapenem resistance. In the present study real-time multiplex PCR was performed to identify the most common carbapenemase genes in 15 non-duplicate carbapenem-resistant A. baumannii isolates collected in 2012. The results showed lack of KPC, GES, VIM, IMP-type enzymes. Four A. baumannii isolates tested positive by PCR for the acquired OXA-24 together with the intrinsic OXA-51 carbapenemase. OXA-24 and OXA-23 were determined as co-existent in one isolate. Two isolates were identified with OXA-23 in addition to the OXA-51 carbapenemase.     

First report of the bla(OXA-58) gene in a clinical isolate of Acinetobacter baumannii in Rio de Janeiro, Brazil

Carbapenemase production is an important mechanism of carbapenem resistance among nonfermentative Gram-negative isolates. This study aimed to report the detection of bla(OXA-58) gene in multiresistant clinical isolates of Acinetobacter baumannii recovered from inpatients in a public hospital. Polymerase chain reaction tests were performed to detect the bla(OXA-23-like), bla(OXA-24-like), bla(OXA-58-like) and bla(OXA-51-like) genes. The bla(OXA-58) and bla(OXA-23) genes were detected in one and three isolates, respectively. Sequencing of the bla(OXA-58-like) amplicon revealed 100% identity with the A. baumannii bla(OXA-58) gene listed in the GenBank database. This is the first report of an OXA-58-producing A. baumannii isolate in Rio de Janeiro, Brazil.     

Rapid Molecular Characterization of Acinetobacter baumannii Clones with rep-PCR and Evaluation of Carbapenemase Genes by New Multiplex PCR in Hospital District of Helsinki and Uusimaa

Multidrug-resistant Acinetobacter baumannii (MDRAB) is an increasing problem worldwide. Prevalence of carbapenem resistance in Acinetobacter spp. due to acquired carbapenemase genes is not known in Finland. The purpose of this study was to examine prevalence and clonal spread of multiresistant A. baumannii group species, and their carbapenemase genes. A total of 55 Acinetobacter isolates were evaluated with repetitive PCR (DiversiLab) to analyse clonality of isolates, in conjunction with antimicrobial susceptibility profile for ampicillin/sulbactam, colistin, imipenem, meropenem, rifampicin and tigecycline. In addition, a new real-time PCR assay, detecting most clinically important carbapenemase genes just in two multiplex reactions, was developed. The assay detects genes for KPC, VIM, IMP, GES-1/-10, OXA-48, NDM, GIM-1, SPM-1, IMI/NMC-A, SME, CMY-10, SFC-1, SIM-1, OXA-23-like, OXA-24/40-like, OXA-58 and ISAbaI-OXA-51-like junction, and allows confident detection of isolates harbouring acquired carbapenemase genes. There was a time-dependent, clonal spread of multiresistant A. baumannii strongly correlating with carbapenamase gene profile, at least in this geographically restricted study material. The new carbapenemase screening assay was able to detect all the genes correctly suggesting it might be suitable for epidemiologic screening purposes in clinical laboratories.     

Dissemination of transferable CTX-M-type extended-spectrum beta-lactamase-producing Escherichia coli in Korea

AIMS: Among 365 Escherichia coli isolated in 2003, 31 cefotaxime-resistant isolates were obtained from clinical specimens taken from adults hospitalized in Busan, Korea. Six extended-spectrum beta-lactamase (ESBL)-producing isolates were investigated further to determine the mechanism of resistance. METHODS AND RESULTS: These isolates were analysed by antibiotic susceptibility testing, pI determination, plasmid profiles, transconjugation test, PCR-restriction fragment length polymorphism (RFLP), enterobacterial repetitive consensus (ERIC)-PCR and DNA sequencing. All six of these isolates were found to contain the CTX-M-type ESBL genes. Five clinical isolates and their transconjugants produced CTX-M-3. One clinical isolate (K17391) and its transconjugant (trcK17391) produced CTX-M-15. Five clinical isolates also produced another TEM-1. One clinical isolate (K12776) also contained another TEM-52. CTX-M-3 ESBL gene was responsible for the resistance to piperacillin, cephalothin, cefotaxime, cefepime and aztreonam. CTX-M-15 or TEM-52 was especially responsible for the resistance to ceftazidime. CONCLUSIONS: These results appear to represent the in vivo evolution of CTX-M-type beta-lactamase genes (bla(CTX-M-3) --> bla(CTX-M-15)) under the selective pressure of antimicrobial therapy (especially ceftazidime). PCR-RFLP is a reliable method to discriminate CTX-M-15 gene from CTX-M-3 gene. ERIC-PCR analysis revealed that dissemination of CTX-M-3 was not due to a clonal outbreak of a resistant strain but to the intra-species spread of resistance to piperacillin, cephalothin, cefotaxime, cefepime and aztreonam in Korea. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of the occurrence of CTX-M-1 cluster ESBLs in Korea. A more comprehensive survey of these ESBL types from Korea is urgently needed because of the in vivo evolution of CTX-M-15 from CTX-M-3. The emergence of these CTX-M-type ESBLs suggests that diagnostic laboratories should screen for ESBLs with ceftazidime as well as cefotaxime; they should still perform clavulanate synergy tests on resistant isolates.     

Molecular characterization of imipenem-resistant Pseudomonas aeruginosa in Hiroshima, Japan

Pseudomonas aeruginosa showing resistance to imipenem were found in 100 of 1,058 strains (9.5%) from six hospitals (a-f) in Hiroshima City, Japan. Of the 100 strains, 14 (14%) were double disk synergy test positive using sodium mercaptoacetic acid disks, and 18 (18%) were bla(IMP-1) or bla(VIM-2) allele positive by polymerase chain reaction (PCR). Among 100 imipenem-resistant strains, 32 were categorized into multi-drug resistant strains, in which 13 were positive for the metallo-beta-lactamase gene. Fifty-one strains (51%) among the 100 imipenem-resistant strains had elevated RND efflux pump activity against levofloxacin. But only 6 of 51 strains were classified as multi-drug resistant strains. The pulsed field gel electrophoresis analysis of the Spe I-digested DNA from the 100 isolates suggested not only clonal spread but spread of heterogeneous clones started to contribute to the prevalence of metallo-beta-lactamase producing P. aeruginosa strains in Japanese hospitals.     

Prevalence of metallo-beta-lactamase among Pseudomonas aeruginosa and Acinetobacter baumannii in a Korean university hospital and comparison of screening methods for detecting metallo-beta-lactamase

To identify the metallo-beta-lactamases (MBLs) prevalent in Korea, a total of 130 clinical isolates of Pseudomonas aeruginosa and Acinetobacter baumannii (99 P. aeruginosa and 31 A. baumannii) with a reduced susceptibility to imipenem (IPM) and/or ceftazidime (CAZ) was subjected to PCR analyses with primers specific to bla(IMP-1), bla(VIM-1), and bla(VIM-2). In addition, inhibitor-potentiated disk diffusion methods (IPD) using two kinds of substrate-inhibitor combinations (ceftazidime-2-mercaptopropionic acid (2MPA) and imipenem-EDTA) were investigated. Thirty-three isolates (29 P. aeruginosa and 4 A. baumannii) carried bla(VIM-2) and two P. aeruginosa isolates harbored bla(IMP-1). The enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) pattern revealed that many of the VIM-2-producing P. aeruginosa isolates were clonally related, whereas the A. baumannii isolates were diverse. The inhibitor-potentiated disk diffusion test using imipenem-EDTA was highly sensitive and specific for detecting the VIM-2 producer. These results suggest that VIM-2 is an important MBL in P. aeruginosa and A. baumannii in the Korean hospital of this study and that the IMP-1-producing P. aeruginosa has also emerged. Screening for MBLs and strict infection control for these isolates will contribute to prevent further spread of resistance.