title: Distribution of Ambler class A, B and D β-lactamases among Pseudomonas aeruginosa isolates.
abstract: OBJECTIVE
  We determined the prevalence rate of classes A, B and D β-lactamases among extended-spectrum cephalosporin (ESC)-non-susceptible Pseudomonas aeruginosa clinical isolates from burned patients.
  
  
  METHODS
  Disc susceptibility testing was performed on 156 P. aeruginosa isolates collected during 2010 at Prince Salman Hospital in Riyadh, Saudi Arabia. Phenotypic screening of ESBLs and MBLs in the isolates resistant to ceftazidime (MIC>8 mg/L) was carried out. Genes encoding ESBLs and MBL were sought by PCR in ESBL- and MBL-producing isolates.
  
  
  RESULTS
  The resistance rate to ceftazidime was 22.43%. The resistance rates for ESC-non-susceptible P. aeruginosa isolates to piperacillin, piperacillin/tazobactam, cefepime, aztreonam, imipenem, amikacin, gentamicin and ciprofloxacin were 100%, 71.14%, 88.57%, 48.57%, 70.0%, 82.5%, 87.5%, and 90.0% respectively. No resistance was detected to polymyxine B. The prevalence of ESBL and MBL in ESC-non-susceptible P. aeruginosa was 69.44% and 42.85%, respectively. The prevalence of structural genes for VEB-1, OXA-10 and GES ESBLs in P. aeruginosa was 68%, 56% and 20%, respectively. VIM gene was detected in 15 (100%) of MBL-producing isolates. OXA-10 like gene was concomitant with VEB, GES and/or VIM. Eight isolates harbored OXA-10 with VEB (imipenem MIC 6-8 mg/L), while five isolates harbored OXA-10 with VIM (imipenem MIC ≥ 32 mg/L) and one isolate contained OXA-10, VEB and GES (imipenem MIC 8 mg/L). PER was not detected in this study.
  
  
  CONCLUSIONS
  VEB-1 and OXA-10 are the predominant ESBL genes and bla(VIM) is the dominate MBL gene in ESC-non-sensitive P. aeruginosa isolates in Saudi Arabia. VEB, OXA-10 and GES ESBLs have not been reported previously in Saudi Arabia and GES has not been reported previously in Middle East and North Africa.
authors.affiliation: Department of Pharmaceutics and Microbiology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Abdulkader F
authors.initials: AF
authors.lastname: Tawfik
authors.forename: Atef M
authors.initials: AM
authors.lastname: Shibl
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Aljohi
authors.forename: Musaad A
authors.initials: MA
authors.lastname: Altammami
authors.forename: Mohamed H
authors.initials: MH
authors.lastname: Al-Agamy
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002056:Burns / Q000382:microbiology*; D002442:Ceftazidime / Q000494:pharmacology; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D011552:Pseudomonas Infections / Q000382:microbiology*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology*; D012529:Saudi Arabia; D001618:beta-Lactamases / Q000032:analysis* / Q000145:classification / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D002442:Ceftazidime; D001618:beta-Lactamases