Emergence and spread of carbapenem-resistant Acinetobacter baumannii sequence type 191 in a Korean hospital

Emergence and spread of specific carbapenem-resistant Acinetobacter baumannii (CRAB) clones cause a serious therapeutic problem. This study was aimed to investigate the clonal diversity and genetic basis of antimicrobial resistance among the 69 CRAB isolates from 2009 to 2010 in a Korean hospital. All CRAB isolates were found to be sequence type (ST) 2 using the Institute Pasteur’s multilocus sequence typing (MLST) scheme, but classified into two sequence groups and nine pulsotypes. Fifty-six CRAB isolates belonging to two main pulsotypes were found to be ST191 using the Bartual’s MLST scheme. All CRAB isolates showed an extensively drug-resistant phenotype. The bla_OXA-51/bla_OXA-23, bla_AmpC/bla_PER-1 and armA genes were largely responsible for resistance to carbapenems, extended-spectrum β-lactams and aminoglycosides, respectively. The first CRAB strains identified in 2005 in this hospital were found to be ST2 using the Institute Pasteur’s MLST scheme, but showed ST353 using the Bartual’s MLST scheme and different pulsotypes from the CRAB isolates from 2009 to 2010. In conclusion, this is the first report of emergence and spread of A. baumannii ST191 in Korea, as well of the genetic basis of its antimicrobial resistance.     

Nosocomial spread of carbapenem-resistant Acinetobacter baumannii (types ST75 and ST137) carrying blaOXA-23-like gene with an upstream ISAba1 in a Chinese hospital

The most widespread type of carbapenemases among carbapenem-resistant Acinetobacter baumannii (CRAB) belongs to the oxacillinase (OXA) group. A total of 57 CRAB isolates and 20 non-CRAB isolates (i.e., A. baumannii susceptible to carbapenems) were studied to investigate the molecular epidemiology of CRAB isolates and to identify the OXAs responsible for resistance to imipenem. The ISAba1-bla_OXA-23-like gene was detected in all 57 CRAB isolates but was detected in none of the non-CRAB isolates. Pulsed-field gel electrophoresis (PFGE) revealed that clones A and B were the dominant genotypes, and all bla_OXA-23-like gene positive strains were classified as either clone A or B strains. ST75 and ST137 were the most prominent sequence types (STs). Finally, the A. baumannii isolates of clone A, C and F were all demonstrated to be genetically similar to the previously identified European clone II. In conclusion, ST75- and ST137-type CRAB isolates that produced the bla_OXA-23-like gene with an upstream ISAba1 contributed to the nosocomial outbreaks studied in this work.     

Worldwide Dissemination of the blaOXA-23 Carbapenemase Gene of Acinetobacter baumannii1

To assess dissemination of OXA-23–producing strains of Acinetobacter baumannii, we obtained 20 carbapenem-resistant, OXA-23–producing isolates from different regions. Their clonal relationship was assessed by pulsed-field gel electrophoresis and multilocus sequence typing. We identified 8 sequence types, including 4 novel types. All except 2 strains belonged to 2 main European clonal lineages. The bla_OXA-23 gene was either located on the chromosome or on plasmids and associated with 4 genetic structures.     

Acinetobacter calcoaceticus-Acinetobacter baumannii complex species in clinical specimens in Singapore

This study was performed to determine the prevalence, distribution of specimen sources, and antimicrobial susceptibility of the Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) species complex in Singapore. One hundred and ninety-three non-replicate Acb species complex clinical isolates were collected from six hospitals over a 1-month period in 2006. Of these, 152 (78·7%) were identified as A. baumannii, 18 (9·3%) as 'Acinetobacter pittii' [genomic species (gen. sp.) 3], and 23 (11·9%) as 'Acinetobacter nosocomialis' (gen. sp. 13TU). Carbapenem resistance was highest in A. baumannii (72·4%), followed by A. pittii (38·9%), and A. nosocomialis (34·8%). Most carbapenem-resistant A. baumannii and A. nosocomialis possessed the bla(OXA-23-like) gene whereas carbapenem-resistant A. pittii possessed the bla(OXA-58-like) gene. Two imipenem-resistant strains (A. baumannii and A. pittii) had the bla(IMP-like) gene. Representatives of carbapenem-resistant A. baumannii were related to European clones I and II.     

Multicentre investigation of carbapenemase-producing Klebsiella pneumoniae and Escherichia coli in Bulgarian hospitals – Interregional spread of ST11 NDM-1-producing K. pneumoniae

AimThe aim of this study was to investigate the mechanisms of beta-lactam-resistance and the clonal relatedness of carbapenem-nonsusceptible Klebsiella pneumoniae and Escherichia coli isolates, collected consecutively in eight centers in five Bulgarian cities from November 2014 to March 2018. Carbapenemase-producing enterobacteria were detected in all but one centers. Overall, 104 K. pneumoniae and one E. coli were analysed.Materials and methodsAntimicrobial susceptibility and beta-lactamases were analysed. Conjugation experiments, plasmid fingerprinting and replicon typing, as well as MLST and ERIC-PCR were carried out.ResultsKPC-2 (51%) and NDM-1 (47%) were the main carbapenemases identified. KPC-2 producing K. pneumoniae were classified into 10 MLST-types. The four dominating MLST-types ST29, ST15, ST336 and ST902 comprised 79% of the KPC-2 producers. All but one of the NDM-1 producing isolates belonged to the MLST-type ST11 and were found in seven centers. Furthermore, single K. pneumoniae isolates producing VIM-1 (ST147) and OXA-48 (ST15) were identified. In addition to the carbapenemases, the ESBLs CTX-M-15, CTX-M-3, and SHV-12 as well as AmpC enzyme CMY-4 were found. The FIIAs-replicon-type was found in all KPC-2 producers while the A/C-replicons dominated in NDM-1 producing isolates. The single NDM-1 producing E. coli was determined as MLST-Type ST10 (Warwick scheme).ConclusionThe interregional clonal expansion of NDM-1 producing ST11 K. pneumoniae and the dissemination of bla_KPC-2 carrying plasmids were responsible for the spread of carbapenemase-producing K. pneumoniae in Bulgaria. Our findings highlight the urgency to prevent dissemination of these highly transmissible and dangerous lineages.     

A reliable combination method to identification and typing of epidemic and endemic clones among clinical isolates of Acinetobacter baumannii

The multi-drug resistant (MDR) Acinetobacter baumannii as an important nosocomial pathogen has emerged a global health concern in recent years. In this study, we applied three easier, faster, and cost-effective methods including PCR-based open reading frames (ORFs) typing, sequence typing of bla_OXA-51-like and RAPD-PCR method to rapid typing of A. baumannii strains. Taken together in the present study the results of ORFs typing, PCR-sequencing of bla_OXA-51-like genes and MLST sequence typing revealed there was a high prevalence (62%, 35/57) of ST2 as international and successful clone which detected among clinical isolates of multi-drug resistant A. baumannii with ORF pattern B and bla_OXA-66 gene. Only 7% (4/57) of MDR isolates belonged to ST1 with ORF pattern A and bla_OXA-69 gene. Interestingly, we detected singleton ST513 (32%, 18/57) that encoded bla_OXA-90 and showed the ORF pattern H as previously isolated in Middle East. Moreover, our data showed RAPD-PCR method can detect divergent strains of the STs. The Cl-1, Cl-2, Cl-3, Cl-4, Cl-10, Cl-11, Cl-12, Cl-13 and Cl-14 belonged to ST2. While the Cl-6, Cl-7, Cl-8 and Cl-9 belonged to ST513. Only Cl-5 belonged to ST1. It seems that the combination of these methods have more discriminatory than any method separately and could be effectively applied to rapid detection of the clonal complex (CC) of A. baumannii strains without performing of MLST or PFGE.     

125株耐碳青霉烯类抗菌药物鲍氏不动杆菌多位点序列分型

目的了解医院耐碳青霉烯类鲍氏不动杆菌的遗传特征。方法选取耐碳青霉烯类鲍氏不动杆菌分离株,进行多位点序列分型(MLST)。结果选取的125株耐碳青霉烯类鲍氏不动杆菌,7个看家基因中6个等位基因数为1,gpi的等位基因数为3,可变位点数为3;125株菌MLST分析,3个ST型,其中ST 75型有82株,ST92型有20株,ST138型有23株,ST75、ST92与ST138属于同一克隆群。结论医院耐碳青霉烯类鲍氏不动杆菌相对进化较慢,对多种抗菌药物耐药,应严格消毒措施及无菌操作,减少由耐碳青霉烯类鲍氏不动杆菌引起的医院感染;减少抗菌药物的使用,减缓泛耐药菌的产生。     

Evolutionary dynamics of carbapenem-resistant Acinetobacter baumannii circulating in Chilean hospitals

We analyze the evolutionary dynamics of ninety carbapenem-resistant Acinetobacter baumannii (CRAB) isolates collected between 1990 and 2015 in Chile. CRAB were identified at first in an isolate collected in 2005, which harbored the ISAba1-bla_OXA-69 arrangement. Later, OXA-58- and OXA-23-producing A. baumannii strains emerged in 2007 and 2009, respectively. This phenomenon was associated with variations in the epidemiology of OXA-type carbapenemases, linked to nosocomial lineages belonging to ST109, ST162, ST15 (CC15) and ST318 (CC15).     

Clonal complexes 104, 109 and 113 playing a major role in the dissemination of OXA-carbapenemase-producing Acinetobacter baumannii in Southeast Brazil

Carbapenem resistance among Acinetobacter baumannii strains isolated from clinical settings in Brazil has increased dramatically in the last 10 years due to the emergence and dissemination of OXA-type carbapenemase encoding genes. This study aimed to characterize the presence of carbapenem-hydrolyzing class D β-lactamases (CHDL)-encoding genes and clonal complexes playing a major role in the dissemination of OXA-carbapenemase-producing A. baumannii in Southeast Brazil.A total of 74 A. baumannii strains isolated from patients admitted to 4 hospitals in Southeast Brazil were analyzed. Molecular characterization of strains revealed that 67 strains carried bla_OXA-23 (72%), bla_OXA-143 (25%) or both genes (3%). PFGE analysis identified 12 PFGE clusters, grouping 26 pulsotypes. Two PFGE clusters were predominant, comprising more than 66% of OXA-producing A. baumannii isolates. Among 23 representative strains characterized by MLST-UO (Multilocus Sequence Typing Scheme – University of Oxford, http://pubmlst.org/abaumannii/), 14 different STs were identified, of which six were confirmed as novel sequence types (designated as STs 402–407). Most of these isolates belonged to clonal complexes CC104,CC109 or CC113, whereas three STs were singletons (ST339, 403 and 407).In conclusion, the presence of bla_OXA-23- and bla_OXA-143-like genes was not related to specific ST/CC, suggesting that the dissemination of OXA-carbapenemase-encoding genes may involve different STs, in which the spread of OXA-23-like is most likely due to mobile elements (i.e., plasmids). In this regard, CC104, CC109 and CC113 played a major role as predominant CDHL-carrying clones, instead of CC92, which was not identified.     

Molecular epidemiology of carbapenem-resistant Acinetobacter baumannii isolates reveals the emergence of blaOXA-23 and blaNDM-1 encoding international clones in India

Acinetobacter baumannii is a nosocomial pathogen increasingly affecting the critically ill patients and represents a major public health challenge. Carbapenem-resistant A. baumannii (CRAB) is found to be associated with International Clones (ICs) and different classes of carbapenemases. The objective of the present study was to investigate the prevalence of carbapenem resistance genes, clonal relationship and genetic structure of clinical isolates of A. baumannii. In the present study, multi-locus sequence typing (MLST^OX) and analysis were carried out using Oxford scheme for 86 clinical isolates of CRAB along with 11 carbapenem sensitive A. baumannii (CSAB) collected over a period of two years (2014–2016) from two tertiary care hospitals of North India. We observed a high prevalence of the bla_OXA-23-like (97.7%) among the CRAB followed by bla_NDM-1 (29.1%) and bla_OXA58-like (3.5%). Forty-seven Sequence Types (STs) were represented by all 97 isolates, out of which, 28 (59.6%) were novel STs that were assigned to 41 isolates. STs 451 (13%), 447 (7%), 195 (6%) and 848 (5%) were the most common STs. The majority of CRAB isolates (44.3%) belonged to the CC92, followed by the CC447 (15.1%), CC109 (9.3%) and CC110 (3.4%), which corresponds to the IC2, 8, 1 and 7 respectively. Phylogenetic and recombination analysis suggested two major and one minor lineage in the population. Further linkage disequilibrium analysis suggested clonal nature of the population as recombination was noticed at a low frequency, which was not enough to split the clonal relationship. The knowledge of genetic structure of CRAB from this study will be invaluable to illustrate epidemiology, surveillance and understanding its global diversity.     

Molecular characterization of class b carbapenemases in advanced stage of dissemination and emergence of class d carbapenemases in Enterobacteriaceae from Croatia

Carbapenemases involved in acquired carbapenem resistance in Enterobacteriaceae belong to Ambler class A serin β-lactamases, class B metallo-β-lactamases (MBL) or class D OXA-48-like β-lactamases. The aim of the present study was to analyse the molecular epidemiology and the mechanisms and routes of spread of class B and class D carbapenemases in Croatia.In total 68 isolates were analyzed. Antibiotic susceptibility was determined by broth microdilution method. PCR was used to detect antibiotic-resistance genes. Genotyping was performed by rep-PCR and MLST.Sixty-five isolates were found to harbour VIM-1 carbapenemase, seven of which were positive also for NDM-1, while two strains harboured only NDM-1. OXA-48 was detected in three isolates, two of which coproduced VIM-1. Thirty-six strains possessed additional CTX-M-15 β-lactamase whereas 64 were positive for TEM-1. CMY was found in 18 Citrobacter freundii isolates and DHA-1 in one Enterobacter cloacae isolate. Four different plasmid-incompatibility groups were found: A/C, L/M, N and FIIAs. Unlike C. freundii and E. cloacae, Klebsiella pneumoniae showed high diversity of rep-PCR patterns. E. cloacae and C. freundii predominantly belonged to one large clone which was allocated to ST105 and ST24, respectively.Three different types of carbapenemases were identified showing the complexity of CRE in Croatia.     

PmrB mutations including a novel 10-amino acid repeat sequence insertion associated with low-level colistin resistance in carbapenem-resistant Acinetobacter baumannii

The global emergence of colistin resistance in carbapenem-resistant Acinetobacter baumannii (CRAB) clinical isolates is a serious public health concern. We therefore aimed to investigate colistin resistance mechanisms in 5 colistin-resistant (COL-R) CRAB isolates collected from Thai patients in 2016 by whole genome sequencing (WGS) compared with those of 5 colistin-intermediate (COL-I) CRAB isolates from the same period. All isolates were subjected to antimicrobial susceptibility testing, efflux pump inhibitor-based test and WGS. Mutations in known genes associated with colistin resistance were analyzed and deleterious mutations were then predicted by PROVEAN tool. The 10 CRAB isolates carried bla_OXA-23 with the addition of bla_OXA-58 in 1 isolate. All COL-R isolates exhibited colistin MICs of 4 μg/mL except for 1 isolate with that of 16 μg/mL. They belonged to ST2, ST16, ST23, ST164 and ST215, whereas the COL-I isolates with colistin MICs of ≤0.25–1 μg/mL were ST2, ST164 and ST215. Neither increased efflux pump activity nor mcr gene was found in any COL-R isolate. Three COL-R isolates contained different PmrB variants: a novel 10-amino acid (aa) repeat sequence insertion, VILGCILIFS between positions 27 and 28 (S27_A28insVILGCILIFS) in transmembrane domain (TM); a 1-aa insertion, alanine between positions 162 and 163 (A162_I163insA) in TM; and a 1-aa substitution, A226T in histidine kinase domain. One COL-R isolate possessed PmrA variant with A80V substitution. These alterations were predicted as deleterious. Mechanisms of colistin resistance in the remaining COL-R isolate were still unknown. In conclusion, the alterations in both PmrB and PmrA were predicted and suggested as initial mutations responsible for low-level colistin resistance in our CRAB isolates. Under selective pressure, these isolates may exhibit higher level colistin resistance by the additional mutations, leading to more therapeutic difficulties.     

Emergence of carbapenem resistant Escherichia coli isolates producing blaNDM and blaOXA-48-like carried on IncA/C and IncL/M plasmids at two Iranian university hospitals

The emergence of carbapenem resistance among Escherichia coli is a serious threat to public health. The objective of this study was to investigate resistance genes and clonality of carbapenem resistant E. coli in Iran. Between February 2015 and July 2016, a total of 32 non-duplicate E. coli isolates that were ertapenem resistant or intermediate (R/I-ETP) were collected from patient clinical or surveillance cultures (rectal swabs) at two university hospitals. Resistance genes were identified by PCR and sequencing. Conjugation experiments, PCR-based replicon typing, PFGE and multilocus sequence typing (MLST) were performed. PCR assays showed, among the 32 isolates, twenty-nine strains produced carbapenemase genes. The predominant carbapenemase was bla_OXA-48 (82.8%), followed by bla_NDM-1 (31%), bla_NDM-7 (6.9%) and bla_OXA-181 (3.4%). Seven of the bla_NDM positive isolates co-harbored bla_OXA-48 carbapenemases. The bla_NDM and bla_OXA-48 were found in IncA/C and IncL/M conjugative plasmids, respectively. The bla_CTX-M-15, qnrA and intI1 genes were also present in most isolates. The PFGE revealed genetic diversity among the 28 E. coli isolates, which belonged to six minor PFGE clusters and 14 isolates were singletons. The 26 isolates were distributed into 18 STs, of which two were dominant (ST648 and ST167). We identified one bla_NDM-1-positive ST131 E. coli isolates that harbor the bla_CTX-M-15 and bla_TEM genes. Horizontal transfer of IncA/C and IncL/M plasmids has likely facilitated the spread of the bla_OXA-48 and bla_NDM genes among E. coli. Their clonal diversity and the presence of faecal carriers in isolates suggest an endemic spread of OXA-48 and NDM. Therefore, it emphasizes the critical importance of monitoring and controlling the spread of carbapenem resistant E. coli.     

Sequential outbreaks of multidrug-resistant Acinetobacter baumannii in intensive care units of a tertiary referral hospital in Italy: combined molecular approach for epidemiological investigation

A laboratory-based surveillance study was conducted from January 2007 to May 2010 in San Martino Tertiary Referral Hospital in Genoa, Italy in which the molecular epidemiology of multidrug-resistant Acinetobacter baumannii was investigated in the five intensive care units (ICUs). A total of 53 A.?baumannii strains were isolated from patients admitted to ICUs (69.8%) and to other epidemiologically linked hospital wards (30.2%) and were genotyped by repetitive extragenic palindromic polymerase chain reaction (REP-PCR), multilocus sequence typing (MLST) and adeB sequence typing. REP-PCR fingerprinting analysis, MLST and adeB typing results were well correlated and allowed us to classify strains causing epidemic events into three major epidemic clones: A (REP-I/ST4, adeB-STII genotype) isolated for the first time in May 2007, B (REP-IV/ST95, adeB-STI genotype) from November 2007 to May 2009 and C (REP-VII/ST118, adeB-STII genotype) from July 2008 to May 2010. MLST results demonstrated that epidemic clones A and C were related as they were members of the widespread clonal complex CC92. The genetic determinants of carbapenem resistance were investigated and resistance associated with the presence of the bla(OxA-58-like) gene with ISAba2 and ISAba3 elements flanking it in clone A, and with the bla(OxA-23-like) gene flanked by ISAba1 in clones B and C. A?molecular approach allowed the prompt introduction of infection control measures and the evaluation of data in a global epidemiological context.     

耐碳青酶烯类鲍氏不动杆菌blaOXA基因型检测及同源性分析

目的了解碳青酶烯类耐药鲍氏不动杆菌的耐药性、blaOXA基因型及同源性。方法琼脂稀释法测定鲍氏不动杆菌对14种抗菌药物的最低抑菌浓度(MIC),PCR扩增ISAba1、blaOXA23和bla OXA-66/OXA-51基因,脉冲场凝胶电泳(PFGE)分析基因同源性。结果20株鲍氏不动杆菌对亚胺培南和美罗培南均耐药,其中19株为多药耐药株,1株ISAba1和blaOXA-23阳性,2株blaOXA-66阳性,16株ISAba1、blaOXA-23和blaOXA-66均阳性,1株以上3种基因全部阴性;PFGE分析结果显示,A型(12株)、B型(2株)、C型(2株)、D型(3株)、E型(1株)。结论医院感染的鲍氏不动杆菌对碳青酶烯类耐药可能与产OXA-23酶有关,并存在院内的克隆传播。     

Molecular characterization of NDM-1-producing Klebsiella pneumoniae ST29, ST347, ST1224, and ST2558 causing sepsis in neonates in a tertiary care hospital of North-East India

Geographical differences can manifest in different spectra of microorganisms and patterns of antibiotic resistance. Considering this, Enterobacteriacae isolated from septicemic neonates from a tertiary care centre in Agartala, India were studied with focus on carbapenem resistance. Two hundred non-duplicate Enterobacteriaceae, of which 12 NDM-1-producing Klebsiella pneumoniae were recovered. Antibiotic susceptibility tests and detection of ESBLs and carbapenemases were performed for all Enterobacteriaceae. For NDM-1-producing isolates, plasmid-mediated quinolone resistance genes, addiction systems, genetic environment of bla_NDM-1 and virulence genes was investigated by PCR. Bacterial clonal relatedness was established using REP-PCR, PFGE, and multi-locus sequence typing (MLST). Transferability of bla_NDM-1 was tested by conjugation and transconjugants were characterized.K. pneumoniae was the primary organism causing sepsis in neonates. Resistance to different antimicrobials was high except for aminoglycosides and carbapenems. bla_CTX-M was present in all isolates. All carbapenem-resistant isolates harboured bla_NDM-1 as the only carbapenemase. bla_CTX-M-15 and qnrS1 were detected in all NDM-1-producing isolates. Plasmid analysis of transconjugants revealed that bla_NDM-1 along with bla_CTX-M-15, qnrS1, qnrB1, aac(6′)-Ib, aac(6′)-Ib-cr and ccdAB or vagCD addiction systems were carried on large IncFIIK conjugative plasmids of varied sizes. bla_NDM-1 was associated with ISAba125 or ISEc33 element at its 5′-end. In addition, isolates also harboured wabG, uge, fimH, mrkD, and entB virulence genes. The NDM-1-producing K. pneumoniae belonged to four distinct clones and were distributed in 4 STs (ST347, ST29, ST2558, and ST1224), of which ST347 was predominant. The association of bla_NDM-1 with diverse STs in K. pneumoniae from neonates indicates the promiscuity of the gene and its widespread dissemination.     

VIM-1 metallo-beta-lactamase in Acinetobacter baumannii

In 2004 and 2005, 5 metallo-beta-lactamase (MBL)-positive Acinetobacter baumannii isolates were found in 2 Greek hospitals. Isolates were unrelated and carried blaVIM-1 in a class 1 integron; bla(OXA-51-) and bla(OXA-58-like) carbapenemase genes were also detected. VIM-1 MBL in Acinetobacter spp. causes concern, given the increasing resistance of this species.     

Molecular epidemiology of carbapenem non-susceptible Acinetobacter nosocomialis in a medical center in Taiwan

The mechanism by which carbapenem non-susceptible Acinetobacter nosocomialis (CNSAN) is disseminated is rarely described in the literature. In this study, we delineated the molecular epidemiology of CNSAN isolated from patients in a medical center in Taiwan. Fifty-four non-duplicate bloodstream isolates of CNSAN were collected at the Taipei Veterans General Hospital between 2001 and 2007. Pulsed-field gel electrophoresis (PFGE) was performed to determine their clonal relationship. Carbapenem-resistance genes and associated genetic structures were detected by polymerase chain reaction (PCR) mapping. Southern hybridization was performed to determine the plasmid location of carbapenem-resistance genes. Transmissibility of these genes to Acinetobacter baumannii was demonstrated by conjugation tests. The overall carbapenem non-susceptibility rate among A. nosocomialis isolates during the study period was 21.6% (54/250). PFGE revealed three major pulsotypes: H (n = 23), I (n = 10), and K (n = 8). The most common carbapenem-resistance gene was bla_OXA-58 (43/54, 79.6%), containing an upstream insertion sequence IS1006 and a truncated ISAba3 (IS1006-ΔISAba3-like-bla_OXA-58). All isolates belonging to the pulsotypes H, I, and K carried plasmid located IS1006-ΔISAba3-like-bla_OXA-58. A common plasmid carrying ISAba1-bla_OXA-82 was found in six isolates, which belonged to five pulsotypes. A type 1 integron that carried bla_IMP-1 was detected in different plasmids of seven isolates, which belonged to five pulsotypes. Plasmids carrying these carbapenem-resistant determinants were transmissible from A. nosocomialis to A. baumannii via conjugation. In this medical center, CNSAN mainly emerged through clonal dissemination; propagation of plasmids and integrons carrying carbapenem-resistant determinants played a minor role. This study showed that plasmids carrying carbapenem-resistant determinants are transmissible from A. nosocomialis to A. baumannii.     

Endemic carbapenem-resistant Pseudomonas aeruginosa with acquired metallo-beta-lactamase determinants in European hospital

Acquired metallo-beta-lactamases (MBLs) can confer broad-spectrum beta-lactam resistance (including carbapenems) not reversible by conventional beta-lactamase inhibitors and are emerging resistance determinants of remarkable clinical importance. In 2001, multidrug-resistant Pseudomonas aeruginosa carrying bla(VIM) MBL genes were found to be widespread (approximately 20% of all P. aeruginosa isolates and 70% of the carbapenem-resistant isolates) at Trieste University Hospital. Clonal diversity and heterogeneity of resistance determinants (either bla(VIM-1)-like or bla(VIM-2)-like) were detected among MBL producers. This evidence is the first that acquired MBLs can rapidly emerge and establish a condition of endemicity in certain epidemiologic settings.     

2008 - 2014年北京市山夫登堡沙门菌耐药性及分子流行病学特征分析

目的 分析北京市2008 - 2014年山夫登堡沙门菌临床分离株的分子流行病学特征。方法 对从腹泻病例分离到的91株山夫登堡沙门菌进行药敏试验、脉冲场凝胶电泳（PFGE）分子分型及多位点序列分型（MLST）。结果 2011 -2012年山夫登堡沙门菌在北京地区高水平流行,占所有分离株的87.9%,2008 - 2010年,2013 - 2104年各年份高度散发,病例主要集中在20～59岁成人组,5 - 6月为发病高峰;所有菌株对萘啶酸有较高耐药性（76.9%）,对磺胺异噁唑（53.9%）和链霉素（49.5%）中度耐药,对其他抗菌药物均较敏感;PFGE分型将91株腹泻株分成23种型别,形成三大克隆群,引起2011 - 2012年暴发流行的64株菌形成绝对优势克隆株;42株菌的MLST分型结果显示包括暴发流行在内的绝大多数菌株属于常见型ST14,5株散发菌株为新型ST1923。结论 北京市山夫登堡沙门菌具有明显的克隆株优势带型,引起2011 - 2012年的本地流行,对抗生素敏感性较高。