title: Phenotypic and genotypic characteristics of tetracycline resistant Acinetobacter baumannii isolates from nosocomial infections at Tehran hospitals.
abstract: OBJECTIVE
  To date, the most important genes responsible for tetracycline resistance among Acinetobacter baumannii isolates have been identified as tet A and tet B. This study was carried out to determine the rate of resistance to tetracycline and related antibiotics, and mechanisms of resistance.
  
  
  METHODS
  During the years 2010 and 2011, a total of 100 A. baumannii isolates were recovered from patients in different hospitals of Tehran, Iran. Antimicrobial susceptibility to tetracycline, minocycline, doxicycline and tigecycline was evaluated by E-test. Polymerase chain reaction (PCR) of the tet A and tet B genes was performed using specific primers, after which the isolates were subjected to Repetitive Extragenic Palindromic-PCR (PCR) to identify the major genotypes.
  
  
  RESULTS
  Of all isolates, 89% were resistant to tetracycline (MIC50 = 32 µg/ml, MIC90 = 512 µg/ml). Minocycline with the resistant rate of 35% (MIC50 = 16 µg/ml, MIC90 =32 µg/ml) and doxicycline with the resistant rate of 25% (MIC50 = 16 µg/ml, MIC90= 32 µg/ml) have a good activity against A. baumannii isolates. All isolates were sensitive to tigecycline. Frequencies of tet B and tet A genes and coexistence of tet A and tet B among the isolates resistant to tetracycline, were 87.6%, 2.2% and 1.1%, respectively. Distribution of REP-types among A. baumannii isolates was types A (40%), B (30%), C (10%), D (5%) and E (5%).
  
  
  CONCLUSIONS
  It seems that tet A and tet B genes play an important role in the induction of resistance towards tetracyclines used in this study. It is suggested that further studies focus on other antimicrobial drugs and combinations in order to achieve a successful therapy against multi drug resistance (MDR) A. baumannii strains in Iran.
authors.affiliation: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Mohammad Hossein
authors.initials: MH
authors.lastname: Maleki
authors.affiliation: Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Putra, Malaysia.
authors.forename: Zamberi
authors.initials: Z
authors.lastname: Sekawi
authors.affiliation: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran ; Department of Microbiology, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Setareh
authors.initials: S
authors.lastname: Soroush
authors.affiliation: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran ; Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Putra, Malaysia.
authors.forename: Farid
authors.initials: F
authors.lastname: Azizi-Jalilian
authors.affiliation: Psychosocial Injuries Research Center, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Khairollah
authors.initials: K
authors.lastname: Asadollahi
authors.affiliation: Department of Microbiology, School of Medicine, Ilam University of Medical Sciences, Ilam, Iran.
authors.forename: Sattar
authors.initials: S
authors.lastname: Mohammadi
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: Clinical Microbiology Research Center, Ilam University of Medical Sciences, Ilam, Iran ; Department of Medical Microbiology and Parasitology, Faculty of Medicine and Health Sciences, University of Putra, Malaysia.
authors.forename: Morovat
authors.initials: M
authors.lastname: Taherikalani
keywords: Acinetobacter baumannii; REP-PCR; Tet A; Tet B; Tetracycline resistance