title: Phenotypic and Genetic Characterization of Carbapenemase and ESBLs Producing Gram-negative Bacteria (GNB) Isolated from Patients with Cystic Fibrosis (CF) in Tehran Hospitals.
abstract: BACKGROUND
  Cystic Fibrosis (CF) is an autosomal recessive genetic disorder in white populations caused by mutation in a gene that encodes Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein. Since frequent respiratory tract infections are the major problem in patients with CF, obligation to identify the causative bacteria and determining their antibiotic resistance pattern is crucial. The purpose of this project was to detect Gram-negative bacteria (GNB) isolated from sputa of CF patients and to determine their antibiotic resistance pattern.
  
  
  METHODS
  The sputum of 52 CF patients, treated as inpatients at hospitals in Tehran, was obtained between November 2011 and June 2012. Samples cultured in selective and non-selective media and GNB recognized by biochemical tests. Antimicrobial susceptibility testing to cephalosporins, aminoglycosides and carbapenems was performed by disk diffusion method and MICs of them were measured. For phenotypic detection of carbapenemase and ESBLs production, the Modified Hodge test, double disk synergy test and the combined disk methods were performed. Subsequently, the genes encoding the extended spectrum beta-lactamases (blaPER, blaCTX-M) and carbapenemases (blaIMP-1, blaGES, blaKPC, blaNDM, blaVIM-1, blaVIM-2, blaSPM, blaSIM) in Gram negative bacteria were targeted among the resistant isolates by using PCR. PFGE was used to determine any genetic relationship among the Pseudomonas aeruginosa isolated from these patients.
  
  
  RESULTS
  Fifty five GNB were isolated from 52 sputum samples including Pseudomonas aeruginosa, Klebsiella ozaenae, Alcaligenes xylosoxidans, Achromobacter denitrificans, Klebsiella pneumonia and Stenotrophomonas maltophilia. The rates of resistance to different antibiotic were as follows: cefixime (%80), ceftriaxone (%43), ceftazidime (%45) and meropenem (%7). The prevalence of genes encoding the ESBLs and Carbapenemases among the the phenotypically positive strains were as follows: blaCTX-M (19), blaIMP-1 (2), blaVIM-1 (2) and blaVIM-2 (3) genes respectively. No other genes were detected. PFGE analysis revealed 8 genotypes. Six isolates had mutually 3 similar patterns.
  
  
  CONCLUSIONS
  This study showed the existence of important ESBLs and carbapenemases genes among the GNB isolated from patients with CF. Continuous surveillance of ESBLs and Carbapenemases, also identification of their types, in bacteria isolated from these patients have an important clinical impact, since, it can often provide valuable information for effective infection control measures and for the choice of appropriate antimicrobial therapy.
authors.affiliation: Student, Department of Microbiology and Microbiology Research Centre, Pasteur Institute , Tehran, Iran .
authors.forename: Parisa
authors.initials: P
authors.lastname: Vali
authors.affiliation: Associate Professor, Department of Microbiology and Microbiology Research Centre, Pasteur Institute , Tehran, Iran .
authors.forename: Fereshteh
authors.initials: F
authors.lastname: Shahcheraghi
authors.affiliation: M.Sc. Student, Department of Microbiology and Microbiology Research Centre, Pasteur Institute , Tehran, Iran .
authors.forename: Maryam
authors.initials: M
authors.lastname: Seyfipour
authors.affiliation: M.Sc. Student, Department of Microbiology and Microbiology Research Centre, Pasteur Institute , Tehran, Iran .
authors.forename: Maryam Alsadat
authors.initials: MA
authors.lastname: Zamani
authors.affiliation: M.Sc. Student, Department of Microbiology and Microbiology Research Centre, Pasteur Institute , Tehran, Iran .
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Allahyar
authors.affiliation: Professor, Department of Microbiology, Faculty of Medicine, Tehran University of Medical Science , Tehran, Iran .
authors.forename: Mohammad Mehdi
authors.initials: MM
authors.lastname: Feizabadi
keywords: Carbapenemase; Cystic fibrosis; Gram-negative Bacteria (GNB); Polymerase Chain Reaction