title: Prevalence of Extended-Spectrum and Metallo β-Lactamase Production in AmpC β-Lactamase Producing Pseudomonas aeruginosa Isolates From Burns.
abstract: BACKGROUND
  Pseudomonas aeruginosa is one of the most common causes of nosocomial infections. Resistance of P. aeruginosa to β-lactam antibiotics may be the result of acquired resistance through mutation and over production of various antibiotic inactivating enzymes. This research aimed to determine the prevalence of extended-spectrum β-lactamases (ESBL) and metallo β-lactamase (MBL) production as well as the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns.
  
  
  OBJECTIVE
  The current study aimed to determine the prevalence of class A ESBL and MBL production in relation to the presence of their related genes among AmpC β-lactamase producing P. aeruginosa isolated from burns.
  
  
  METHODS
  The antimicrobial susceptibility of 51 P. aeruginosa isolates from patients with burns was examined against 13 antibiotics by the disc diffusion method. Minimum inhibitory concentrations (MIC) for imipenem and ceftazidime were measured by the microdilution method. AmpC production was detected by AmpC disc and the modified three-dimensional extract tests. ESBL phenotype was confirmed by the double disc synergy test (DDST). Presence of β-lactamase genes was detected by specific primers and polymerase chain reaction (PCR).
  
  
  RESULTS
  All isolates were multidrug resistant. AmpC, ESBL and MBL production were observed in 35 (68.6%), 20 (39.2%) and 19 (37.3%) isolates, respectively. Overall, 43 isolates (84.3%) carried β-lactamase genes, out of which 31 (60.8%) harbored bla AmpC , 20 (39.2%) had bla TEM and 11 (21.6%) carried bla PER -1 genes. Among the AmpC producers, two isolates (6.5%) carried bla AmpC + bla ESBL , 13 (41.9%) had bla AmpC + bla MBL and six (19.4%) produced the three enzymes.
  
  
  CONCLUSIONS
  A high prevalence of multiple β-lactamase production was observed among the AmpC producers (60%), of which the majority co-produced AmpC and MBL. The current study results showed correlation between β-lactamase production and the presence of antibiotic resistance genes in the isolates.
authors.affiliation: Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, IR Iran.
authors.forename: Roya
authors.initials: R
authors.lastname: Rafiee
authors.affiliation: Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, IR Iran.
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Eftekhar
authors.affiliation: Department of Pediatrics, Shahid Beheshti University of Medical Sciences, Tehran, IR Iran.
authors.forename: Seyyed Ahmad
authors.initials: SA
authors.lastname: Tabatabaei
authors.affiliation: Department of Microbiology, Faculty of Biological Sciences, Shahid Beheshti University, Tehran, IR Iran.
authors.forename: Dariush
authors.initials: D
authors.lastname: Minaee Tehrani
keywords: Beta-Lactamase; Pseudomonas aeruginosa; blaAMPC; blaESBL; blaMBL