title: Detection and spread of carbapenem-resistant Citrobacter freundii in a teaching hospital in China.
abstract: BACKGROUND
  We examined the detection and spread of carbapenem-resistant Citrobacter freundii in Huashan Hospital, Shanghai, China between 2005 and 2008.
  
  
  METHODS
  Twenty-three isolates of carbapenem-resistant C freundii collected in our hospital underwent resistant gene amplification by polymerase chain reaction, followed by minimal inhibitory concentration (MIC) analysis. Molecular epidemiologic analyses included pulsed-field gel electrophoresis and case study.
  
  
  RESULTS
  Analysis of MICs with amikacin, gentamicin, cefotaxime, ceftazidime, cefepime, imipenem, meropenem, ertapenem, cefoxitin, piperacillin-tazobactam, and ciprofloxacin characterized the isolates as highly resistant to antimicrobials. Colistin, tigecycline, minocycline, and doxycycline to all C freundii isolates had lower MICs than the other antimicrobials tested, with MIC(50)/MIC(90) values of 0.5/1, 1/1, 4/8, and 4/4 mg/L, respectively. Molecular typing using pulsed-field gel electrophoresis classified the isolates into 4 groups, of which 15 isolates belonged to a single clone. In total, all of the isolates produced KPC-2-type carbapenemase, of which most were likely to couple with CTX-M-type extended-spectrum β-lactamases and plasmid-mediated CMY-2-type AmpC enzyme. Subsequent clinical investigations involving the general status of patients, the ward, and antimicrobial and therapeutic outcomes showed that a carbapenem-resistant clone had spread critically in the Department of Neurosurgery. Potential risk factors were identified, including invasive procedures, surgical operations, use of indwelling urine catheters, and number of sickbed changes.
  
  
  CONCLUSIONS
  The spread of carbapenem-hydrolyzing C freundii isolates has emerged in regional hospitals in China. Multidrug-resistant mechanisms of strains severely hamper control efforts. Our findings should alert clinicians to issues involved with preventing the spread of carbapenem-resistant C freundii.
authors.affiliation: State Key Laboratory of Genetic Engineering, Institute of Genetics, School of Life Sciences, Fudan University, Shanghai, China.
authors.forename: Shudan
authors.initials: S
authors.lastname: Chen
authors.forename: Fupin
authors.initials: F
authors.lastname: Hu
authors.forename: Yang
authors.initials: Y
authors.lastname: Liu
authors.forename: Demei
authors.initials: D
authors.lastname: Zhu
authors.forename: Honghai
authors.initials: H
authors.lastname: Wang
authors.forename: Yingyuan
authors.initials: Y
authors.lastname: Zhang
mesh_terms: D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D002681:China; D016971:Citrobacter freundii / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D016000:Cluster Analysis; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology; D004269:DNA, Bacterial / Q000235:genetics; D016521:Electrophoresis, Gel, Pulsed-Field; D004756:Enterobacteriaceae Infections / Q000453:epidemiology* / Q000382:microbiology; D005260:Female; D005838:Genotype; D006784:Hospitals, Teaching; D006801:Humans; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; D004269:DNA, Bacterial