title: Detection of AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.
abstract: OBJECTIVE
  Pseudomonas aeruginosa is responsible for devastating nosocomial infections among severely burn patients. Class C of cephalosporinase (AmpC-β-lactamases) is important cause of multiple β-lactam resistance in P. aeruginosa. The aim of this study was to detect the AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.
  
  
  METHODS
  a total of 100 isolates of carbapenem resistant P. aeruginosa isolates from different burn patients were investigated. Three phenotypic methods were selected for identification of the AmpC-β-lactamases producing isolates.
  
  
  RESULTS
  Fifty four isolates were AmpC producer as detected by AmpC disk test. Seventeen isolates were identified as AmpC producer using combined disk method. Fifty two isolates showed a twofold or threefold dilution difference between the minimum inhibitory concentration of imipenem or ceftazidime and the minimum inhibitory concentration of imipenem or ceftazidime plus cloxacillin. One isolate was identified as AmpC producer using three methods. Three isolates produced AmpC as detected by both AmpC disk test and combined disk methods and 19 isolates were found as AmpC producer using both AmpC disk test and minimum inhibitory concentration methods. Six isolates were AmpC producer as shown by the MICs of both imipenem and ceftazidime.
  
  
  CONCLUSIONS
  According to the results of this study, AmpC- β-lactamase looks to be the main mechanism of resistance of Pseudomonas aeruginosa to cephalosporins and carbapenems in the study hospital.
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.
authors.forename: Akbar
authors.initials: A
authors.lastname: Mirsalehian
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.
authors.forename: Davood
authors.initials: D
authors.lastname: Kalantar-Neyestanaki
authors.affiliation: Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Keramat
authors.initials: K
authors.lastname: Nourijelyani
authors.affiliation: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Kheirollah
authors.initials: K
authors.lastname: Asadollahi
authors.affiliation: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Morovat
authors.initials: M
authors.lastname: Taherikalani
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Emaneini
authors.affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Jabalameli
keywords: AmpC-β-lactamases; Pseudomonas aeruginosa; β-lactam resistance
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