title: Molecular characterization of clinical multidrug-resistant Klebsiella pneumoniae isolates.
abstract: BACKGROUND
  Klebsiella pneumoniae is a frequent nosocomial pathogen, with the multidrug-resistant (MDR) K. pneumoniae being a major public health concern, frequently causing difficult-to-treat infections worldwide. The aim of this study was to investigate the molecular characterization of clinical MDR Klebsiella pneumoniae isolates.
  
  
  METHODS
  A total of 27 non-duplicate MDR K. pneumoniae isolates with a CTX-CIP-AK resistance pattern were investigated for the prevalence of antimicrobial resistance genes including extended spectrum β-lactamase genes (ESBLs), plasmid-mediated quinolone resistance (PMQR) genes, 16S rRNA methylase (16S-RMTase) genes, and integrons by polymerase chain reaction (PCR) amplification and DNA sequencing. Plasmid replicons were typed by PCR-based replicon typing (PBRT). Multi-locus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) were carried out to characterize the strain relatedness.
  
  
  RESULTS
  All the isolates co-harbored 3 or more resistance determinants. OqxAB, CTX-M-type ESBLs and RmtB were the most frequent determinants, distributed among 19 (70.4%),18 (66.7%) and 8 (29.6%) strains. Fourteen isolates harbored class 1 integrons, with orfD-aacA4 being the most frequent gene cassette array. Class 3 integrons were less frequently identified and contained the gene cassette array of blaGES-1-blaOXA-10-aac(6')-Ib. IncFII replicon was most commonly found in this collection. One cluster was observed with ≥80% similarity among profiles obtained by PFGE, and one sequence type (ST) by MLST, namely ST11, was observed in the cluster.
  
  
  CONCLUSIONS
  K. pneumoniae carbapenemase (KPC)-producing ST11 was the main clone detected. Of particular concern was the high prevalence of multiple resistance determinants, classs I integrons and IncFII plasmid replicon among these MDR strains, which provide advantages for the rapid development of MDR strains.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Cao
authors.forename: Xuejing
authors.initials: X
authors.lastname: Xu
authors.forename: Zhifeng
authors.initials: Z
authors.lastname: Zhang
authors.forename: Han
authors.initials: H
authors.lastname: Shen
authors.forename: Junhao
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Laboratory Medicine, Nanjing Drum Tower Hospital, the affiliated Hospital of Nanjing University Medical School, Zhongshan Road, 321#, Gulou District, Nanjing, Jiangsu Province 210008, PR China. zhangkui6103@163.com.
authors.forename: Kui
authors.initials: K
authors.lastname: Zhang
mesh_terms: D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology; D024901:Drug Resistance, Multiple, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007710:Klebsiella Infections / Q000453:epidemiology / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification* / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017720:Molecular Epidemiology; D058885:Multilocus Sequence Typing; D010957:Plasmids; D016133:Polymerase Chain Reaction