title: Molecular characterisations of integrons in clinical isolates of Klebsiella pneumoniae in a Chinese tertiary hospital.
abstract: BACKGROUND
  Integrons are mobile genetic elements that play an important role in the distribution of antibiotic-resistance genes among bacteria. This study aimed to investigate the distribution of integrons in clinical isolates of Klebsiella pneumoniae and explore the molecular mechanism of integron-mediated multiple-drug resistance in K. pneumoniae.
  
  
  METHODS
  Class 1, 2, and 3 integrases were identified by polymerase chain reaction (PCR) among 178 K. pneumoniae clinical isolates. Antibiotic susceptibility was examined by disk-diffusion method. Conjugation experiments were conducted to evaluate the horizontal-transfer capability, and multilocus sequence typing (MLST) assays were conducted to explore the genetic relationships among the isolates. Highly virulent serotypes were identified by PCR from the 44 integron-positive isolates with variable regions.
  
  
  RESULTS
  Class1 and 2 integrons were detected in 60.1% and 1.7% of isolates, respectively. One isolate carried both class 1 and 2 integrons. Class 3 integrons were not detected in all 178 isolates. Among the 44 integrons containing variable regions, 39 were located in conjugative plasmids. Dihydrofolate reductase (dfrA) and aminoglycoside adenyltransferase (aad) were found to be the most common in class 1 and 2 integrons. These gene cassettes encoded resistance to trimethoprim and aminoglycosides. Moreover, the association between integron carriage and antibiotic resistance was most significant for aminoglycosides, phenicols, and fluoroquinolones. Among the 44 integron-positive isolates with variable regions, 9 were classified as highly virulent serotypes (k1, k2, k20, and k54). In addition, MLST analysis detected 13 sequence types (STs), with the predominant ones being ST11 and ST15. The eBURST analysis revalued the existence of 11 singleton STs and one group, which is comprised of ST11 and ST437.
  
  
  CONCLUSIONS
  The wide diversity of detected integrons suggested that the horizontal transfer by mobile genetic elements played a major role in the distribution of antimicrobial resistance genes, thereby indicating the urgent need to use effective means of avoiding the spread of drug-resistant bacteria.
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Xu
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Xuan
authors.initials: X
authors.lastname: Li
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Mei
authors.initials: M
authors.lastname: Luo
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Pin
authors.initials: P
authors.lastname: Liu
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Kewen
authors.initials: K
authors.lastname: Su
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Qing
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Shuai
authors.initials: S
authors.lastname: Chen
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China.
authors.forename: Jingfu
authors.initials: J
authors.lastname: Qiu
authors.affiliation: Research Center for Medicine and Social Development, Innovation Center for Social Risk Governance in Health, School of Public Health and Management, Chongqing Medical University, Chongqing 400016, China. Electronic address: liylyl@126.com.
authors.forename: Yingli
authors.initials: Y
authors.lastname: Li
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002681:China; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D052978:Disk Diffusion Antimicrobial Tests; D024901:Drug Resistance, Multiple, Bacterial; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D032023:Integrons; D007710:Klebsiella Infections / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D058885:Multilocus Sequence Typing; D016133:Polymerase Chain Reaction; D062606:Tertiary Care Centers
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial
keywords: Integrons; Klebsiella pneumoniae; Multidrug resistance; Multilocus sequence typing