title: Study on imipenem resistance and prevalence of blaVIM1 and blaVIM2 metallo-beta lactamases among clinical isolates of Pseudomonas aeruginosa from Mashhad, Northeast of Iran.
abstract: OBJECTIVE
  The main cause of serious nosocomial infections is a Gram-negative pathogen known as Pseudomonas aeruginosa (P. aeruginosa). Carbapenems are widely used as an appropriate treatment for these infections, however resistance to these agents has been observed and is increasing. Metallo beta-lactamase (MBLs) enzyme is one of the main causes of resistance to carbapenem. In the current study the frequency and production of VIM1 and VIM2 by imipenem-resistant P. aeruginosa isolates of patients hospitalized in Imam Reza hospital were evaluated.
  
  
  METHODS
  In this study, 131 clinical samples were collected from patients hospitalized in Imam Reza hospital in Mashhad during a 15-month period from May 2011 to November 2012. After verification of P. aeruginosa isolates, antibiotic resistance patterns of isolates were determined for 14 antibiotics by Kirby-Bauer standard disk diffusion according to the CLSI guidelines. Combined-disk test was used for phenotypic determination of MBLs-producing isolates and after DNA extraction, genotypic determination of VIM1 and VIM2 metallo beta-lactamase genes was carried out using Multiplex-PCR.
  
  
  RESULTS
  Of 63 imipenem-resistant isolates (48.5%), 56 (88.8%) were MBL-producing in phenotypic assessments. Also amongst imipenem-resistant isolates, the frequency of VIM1 and VIM2 genes were 58.7 and 3.17%, respectively.
  
  
  CONCLUSIONS
  The results of the current study along with the results of the other conducted studies in Iran in recent years demonstrate that the average resistance to imipenem in P. aeruginosa isolates was 51.3% which has increased in comparison with the results in 2006 (32.9%). It was also determined that the frequency of VIM1 gene was more than VIM2 gene. In phenotypic assessment by using CD method, 49.6% of isolates were determined as MBLs-producing. The sensitivity and specificity of this method were verified in comparison with the results of PCR test.
authors.affiliation: Student Research Committee (SRC); Mashhad University of Medical Sciences, Mashhad, Iran. ; Antimicrobial Resistance Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Seyedeh Zohreh
authors.initials: SZ
authors.lastname: Mirbagheri
authors.affiliation: Antimicrobial Resistance Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Meshkat
authors.affiliation: Antimicrobial Resistance Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Mahboubeh
authors.initials: M
authors.lastname: Naderinasab
authors.affiliation: Department of Biology, Faculty of Sciences, Ferdowsi University of Mashhad, Mashhad, Iran.
authors.forename: Sina
authors.initials: S
authors.lastname: Rostami
authors.affiliation: Department of Biotechnology, School of Pharmacy, Mashhad University of Medical Sciences, Mashhad, Iran.
authors.forename: Maryam Sadat
authors.initials: MS
authors.lastname: Nabavinia
authors.affiliation: Microbiology Research Center, Faculty of Medicine, Kerman University of Medical Sciences, Kerman, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Rahmati
keywords: Imipenem; Metallobeta-lactamase genes; Pseudomonas aeruginosa