title: Carbapenem resistance mechanism and risk factors of Pseudomonas aeruginosa clinical isolates from a University Hospital in Xi'an, China.
abstract: OBJECTIVE
  Carbapenems are important agents for the therapy of Gram-negative bacillus infections, and the development of their resistance hampers effective therapeutic options. The purpose of this study was to assess the major mechanisms and risk factors leading to carbapenem resistance in clinical Pseudomonas aeruginosa isolates.
  
  
  METHODS
  Thirty-four clinical isolates with differing degrees of carbapenem susceptibility were analyzed for carbapenemase, porin, and efflux systems. Risk factor analysis was performed using a case-control study.
  
  
  RESULTS
  Eighteen of 24 carbapenem-resistant isolates were producers of carbapenemase. Diminished expression of oprD and overexpression of effluxes were present in five and seven carbapenem-resistant isolates, respectively. The number of days from admission to the day of positive culture and days of antibiotic apply were identified as the independent predictors of infection with carbapenem-resistant P. aeruginosa.
  
  
  CONCLUSIONS
  Carbapenemase production is a major mechanism of P. aeruginosa isolates involved in this study. Increased length of hospital stay and days of antibiotic application were the most important risk factors identified for carbapenem resistance.
authors.affiliation: Department of Microbiology, Fourth Military Medical University, Xi'an, P.R. China. fengql@fmmu.edu.cn
authors.forename: Jian-Fang
authors.initials: JF
authors.lastname: Zhang
authors.forename: Bi-Liang
authors.initials: BL
authors.lastname: Chen
authors.forename: Xiao-Yan
authors.initials: XY
authors.lastname: Xin
authors.forename: Hai-Bo
authors.initials: HB
authors.lastname: Zhao
authors.forename: Hong-Ying
authors.initials: HY
authors.lastname: Wang
authors.forename: Hui
authors.initials: H
authors.lastname: Song
authors.forename: Zhi-Kai
authors.initials: ZK
authors.lastname: Xu
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology*; D016022:Case-Control Studies; D002681:China; D003428:Cross Infection / Q000382:microbiology; D017931:DNA Primers; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial; D006785:Hospitals, University; D006801:Humans; D018272:Porins / Q000235:genetics; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors; D001618:beta-Lactamases / Q000032:analysis / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D017931:DNA Primers; D018272:Porins; C077157:OprD protein, Pseudomonas aeruginosa; D001618:beta-Lactamases; C063912:carbapenemase