Zeqing Wei

ST11, the dominant clone of KPC-producing Klebsiella pneumoniae in China

OBJECTIVES Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae has spread rapidly in China. In this study, we aimed to investigate the molecular epidemiology of KPC-producing K. pneumoniae isolates in China. METHODS Ninety-five carbapenem-resistant K. pneumoniae isolates from 13 hospitals in nine cities covering five provinces in China were analysed. Antibiotic susceptibility was determined by the Etest. Multilocus sequence typing (MLST) and PFGE were used for epidemiological analysis. The genetic structure around bla(KPC) and the encoding genes of extended-spectrum β-lactamases and plasmid-mediated AmpC enzymes were detected by PCR and sequencing. Plasmids were analysed by transformation, restriction and Southern blot. RESULTS All isolates harboured the bla(KPC-2) gene. Seven sequence types (STs) were obtained. The dominant clone was ST11 (61/95), which was identified in isolates from Zhejiang province (four hospitals in Hangzhou and one hospital in Ningbo), Jiangsu province (one hospital in Nanjing) and Anhui province (one hospital in Hefei). Isolates with ST11 showed >80% similarity in PFGE patterns. Plasmids from 14 selected transformants, their original isolates representing different STs and/or regions, had a diversity of HindIII restriction maps. CONCLUSIONS The dominant clone of KPC-producing K. pneumoniae in China is ST11, which is closely related to ST258, which has been reported worldwide.

Plasmid-mediated KPC-2 in a Klebsiella pneumoniae isolate from China.

ABSTRACT A carbapenem-resistant isolate of Klebsiella pneumoniae producing class A carbapenemase KPC-2 was identified in Zhejiang, China. The KPC-2 gene was located on an approximately 60-kb plasmid in a genetic environment partially different from that of blaKPC-2 in the isolates from the United States and Colombia.

Novel Genetic Environment of the Carbapenem-Hydrolyzing β-Lactamase KPC-2 among Enterobacteriaceae in China

ABSTRACT Thirty-nine blaKPC-producing isolates of the family Enterobacteriaceae with carbapenem resistance or reduced carbapenem susceptibility were obtained from inpatients from eight hospitals in six cities of three provinces in eastern China. The pulsed-field gel electrophoresis analysis of all 36 Klebsiella pneumoniae isolates revealed six major patterns. The resistant plasmids of most isolates were successfully transferred by conjugation and evaluated experimentally to be 40 to 180 kb in size. A 20.2-kb blaKPC-surrounding nucleotide sequence from plasmid pKP048 has been obtained and contains an integration structure of a Tn3-based transposon and partial Tn4401 segment, with the gene order Tn3-transposase, Tn3-resolvase, ISKpn8, the blaKPC-2 gene, and the ISKpn6-like element. The chimera of several transposon-associated elements indicated a novel genetic environment of the K. pneumoniae carbapenemase β-lactamase gene in isolates from China.

Wide dissemination of OXA-23-producing carbapenem-resistant Acinetobacter baumannii clonal complex 22 in multiple cities of China

OBJECTIVES In this study, multilocus sequence typing (MLST) was used to describe the genetic backgrounds of carbapenem-resistant Acinetobacter baumannii (CRAB) and carbapenem-susceptible A. baumannii (CSAB) from multiple cities of China. METHODS One hundred and fifty-two CRAB and 74 CSAB isolates obtained from 16 cities of China were selected for molecular characterization by MLST. eBURST was used to cluster sequence types (STs) into clonal complex (CCs) and infer evolutionary descent. PCR was used to detect carbapenemase-encoding genes and bla(AmpC) with the upstream element ISAba1. RESULTS CSAB showed more diverse genetic backgrounds than CRAB since 36 distinct STs were identified in CSAB while only 8 STs were identified in CRAB. ST22 and its three single-locus variants, all clustered into CC22, were the most prominent STs, accounting for 86.8% of CRAB and 45.9% of CSAB, distributed in all 16 cities and possessing more noticeable antibiotic resistance than other STs. PCR amplification was positive for bla(OXA-23) in most CRAB isolates but negative in CSAB isolates. The presence of ISAba1 upstream of bla(AmpC) was variable in distinct STs of CRAB. eBURST reveals that CC22 is the largest group in the Pubmlst database, which also contains ST6 previously identified in a European clone II isolate as a member of a subgroup of CC22. CONCLUSIONS We describe the wide dissemination of CRAB CC22 in China. The close relatedness between CC22 and European clone II implies the probable global spread of CC22. It is inferred that ST22-CSAB evolves to ST22-CRAB through acquiring bla(OXA-23) as a determinative factor.

Epidemiology and characteristics of antimicrobial resistance in China

A comprehensive surveillance system for bacterial resistance in tertiary hospitals has been established in China that involves tertiary hospitals in distinct regions nationwide, enabling the collection of a large amount of antimicrobial surveillance data. Antimicrobial resistance in China has become a serious healthcare problem, with high resistance rates of most common bacteria to clinically important antimicrobial agents. Methicillin-resistant S. aureus, ESBL-producing Enterobacteriaceae and carbapenem-resistant Acinetobacter baumannii represent more than 50% of microbial isolates. Additionally, bacterial resistance to fluoroquinolones, macrolides and third-generation cephalosporins is of serious concern. The molecular epidemiology and resistance mechanisms of the antimicrobial strains in China exhibited regional specificity, as well as the influence of dissemination of international clonal complexes. The molecular characteristics of MRSA, ESBL- and carbapenemase-producing Enterobacteriaceae, and macrolide-resistant gram-positive Streptococci in China were significantly different from those in other countries and regions, while S. pneumoniae serotypes appear to have been affected by the global spread of prevalent clones in other parts of the world. Moreover, important antimicrobial resistant bacteria such as community-acquired-MRSA, multidrug-resistant P. aeruginosa and extensive-resistant A. baumannii, and the antimicrobial resistance in primary healthcare and outpatient setting should be intensely monitored and investigated in the future.

Complete nucleotide sequence of Klebsiella pneumoniae multidrug resistance plasmid pKP048, carrying blaKPC-2, blaDHA-1, qnrB4, and armA.

ABSTRACT The Klebsiella pneumoniae multidrug resistance plasmid pKP048 was completely sequenced. This plasmid carries several important resistance determinants, such as blaKPC-2, blaDHA-1, qnrB4, and armA, which confer resistance to carbapenems, cephalosporins, fluoroquinolones, and aminoglycosides, respectively. Analysis of the finished 151,188-bp sequence data revealed 163 putative genes, 108 of which were assigned functions such as replication, stable inheritance, antibiotic resistance, a mobile element, conjugal transfer, and a restriction-modification system, showing the strong phylogenetic mosaicism and plasticity of the plasmid.

Nationwide high prevalence of CTX-M and an increase of CTX-M-55 in Escherichia coli isolated from patients with community-onset infections in Chinese county hospitals

BackgroundIn order to investigate the epidemiology, molecular characteristics, and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from community-onset infections in Chinese county hospitals.MethodsE. coli isolates were collected from patients with community-onset infections in 30 county hospitals. ESBL activity was confirmed by double-disc diffusion. Genetic confirmation and molecular typing of ESBL- and AmpC-producing isolates was determined by PCR and DNA sequencing. ESBL-positive isolates were further characterised by multi-locus sequence typing.ResultsOf 550 E. coli isolates, 256 (46.5%) carried ESBL genes and all were of the CTX-M type. The prevalence of ESBL-producing strains varied from 30.2% to 57.0% across different regions of China. Overall, 12 blaCTX-M subtypes were detected; the most abundant were blaCTX-M-14 (163/256 isolates, 64.5%), blaCTX-M-55(47/256, 18.4%), and blaCTX-M-15 (31/256, 12.1%). CMY-2-like AmpC β-lactamases were detected in 11 strains, three of which co-existed with blaCTX-M. A total of 64 sequence types (STs) were detected in 256 ESBL-producing strains, including nine that were new. ST131 was the most abundant type (27 isolates, 12.7%), followed by ST69 (14 isolates, 6.6%), ST405 (14 isolates, 6.6%), and ST38 (12 isolates, 5.6%).ConclusionsThis study revealed that the widespread prevalence of ESBLs among outpatient infections has reached a high level in county hospitals. The CTX-M genotype was most dominant, comprising a variety of subtypes. This is the first time the incidence of CTX-M-55 has exceeded that of CTX-M-15 in China. No predominant ST was detected, suggesting that ESBL-producing E. coli strains originate in different clones.

Molecular epidemiology and mechanisms of carbapenem resistance in Pseudomonas aeruginosa isolates from Chinese hospitals

We investigated the molecular epidemiology and carbapenem resistance mechanisms of 258 non-duplicate carbapenem-resistant clinical isolates of Pseudomonas aeruginosa collected from 2006 to 2007 at 28 hospitals in China. Up to 88% of the carbapenem-resistant isolates were multidrug-resistant. Pulsed-field gel electrophoresis (PFGE) revealed that levels of intrahospital and interhospital dissemination of clones were low. To assess the mechanisms leading to resistance, all 258 carbapenem-resistant isolates were analysed for expression of the chromosomal beta-lactamase (AmpC), the porin important for entry of carbapenems (OprD) and an efflux system (MexAB-OprM) known to extrude some beta-lactams. Carbapenem resistance was driven mainly by mutational inactivation of OprD, accompanied or not by hyperexpression of AmpC or MexAB-OprM. Metallo-beta-lactamase genes were detected in 22 carbapenem-resistant isolates in China, belonging to eight pulsotypes. The bla(OXA-50) gene was detected among all of the carbapenem-resistant isolates, whereas the bla(GES-5) gene was detected in only one carbapenem-resistant isolate.

Clonal Spread of Imipenem-Resistant Acinetobacter baumannii among Different Cities of China

ABSTRACT A total of 342 imipenem-resistant Acinetobacter baumannii isolates (IRABs) were collected from 16 Chinese cities. Six predominant clones had spread widely, and four clones were detected in distant hospitals. The majority of the IRABs contain blaOXA-23, with ISAba1 upstream of the gene. These results suggested that clonal spread played an important role in the outbreak of IRABs in China.

Dissemination of a clone carrying a fosA3-harbouring plasmid mediates high fosfomycin resistance rate of KPC-producing Klebsiella pneumoniae in China

Fosfomycin has been proposed as an adjunct to other active agents for treating KPC-producing Klebsiella pneumoniae infections. This study aimed to investigate the prevalence of fosfomycin resistance and plasmid-mediated resistance determinants among KPC-producing K. pneumoniae isolates from clinical samples in China. In total, 278 KPC-producing and 80 extended-spectrum β-lactamase (ESBL)-producing (non-KPC-producing) clinical K. pneumoniae isolates were collected in 12 hospitals from 2010 to 2013. Fosfomycin susceptibility testing was carried out using the agar dilution method. Phylogenetic clonal patterns were revealed by pulsed-field gel electrophoresis (PFGE). Isolates were screened for plasmid-mediated fosfomycin resistance genes (fosA, fosA3 and fosC2) by PCR amplification. A plasmid was completely sequenced by next-generation sequencing. The fosfomycin resistance rate in KPC-producers (60.8%; 169/278) was significantly higher than in ESBL-producers (12.5%; 10/80). In addition, 94 KPC-producing isolates were positive for fosA3 and most of them were clonally related. A 23939-bp plasmid (pFOS18) co-harbouring fosA3 and bla(KPC-2) was completely sequenced, revealing that the fosA3 gene was flanked by two copies of IS26; however, bla(KPC-2) was located on a Tn3-Tn4401 integration structure. Although the fosA3 and blaKPC-2 genes are located on different transposon systems, they are able to spread together worldwide through plasmid transfer. Dissemination of the clone carrying the fosA3-harbouring plasmid mediates the high fosfomycin resistance rate of KPC-producing K. pneumoniae in China. Fosfomycin as an alternative option for treating infections caused by KPC-producing K. pneumoniae should not be recommended in hospitals in which fosfomycin-resistant clonal dissemination is emerging.