title: Survey ofCTX-MGene Frequency in Extended-Spectrum Beta-Lactamase-ProducingEnterobacteriaceaeIsolates Using the Combination Disk and PCR Methods in Ahvaz, Iran.
abstract: BACKGROUND
  A common mechanism of resistance to beta-lactam antibiotics is the production of beta-lactamase by Gram-negative bacteria. Recently, nonderivative extended-spectrum beta-lactamases (ESBLs) from the TEM and SHV enzymes, such as CTX-M, that were related to different geographical regions have been recognized.
  
  
  OBJECTIVE
  The aim of this study was to determine the frequency of theCTX-Mgene in ESBL-producingEnterobacteriaceaeisolates in hospitalized patients in the teaching hospitals of Ahvaz, Iran.
  
  
  METHODS
  Enterobacteriaceaeisolates from clinical specimens (other than stool), such as wounds, blood, urine, trachea, discharge, and abscess, were collected and examined. All the isolates were identified using standard biochemical tests. The combination test was carried out based on CLSI criteria for the phenotypic detection of ESBL-producing isolates. After DNA extraction, theCTX-MandCTX-M-1genes were amplified using PCR among phenotypically positive ESBL isolates.
  
  
  RESULTS
  Among 240Enterobacteriaceaeisolates,Escherichia coliandEnterobacterwere the most common isolates with 171 (71.3%) and 65 (27.1%), respectively. The combination test results also showed that 108 (45%)Enterobacteriaceaeisolates were phenotypic ESBL producers, but 104 (96%) isolates were positive for theblaCTX-Mgene and 99 (92%) were positive for theblaCTX-M-1gene according to the PCR method.
  
  
  CONCLUSIONS
  The results of this study phenotypically and genotypically confirmed the high frequency of ESBL-producing strains, such as theCTX-MandCTX-M-1genes, amongEnterobacteriaceaeisolates in our region. Therefore, use of antibiotic susceptibility testing for the detection of ESBL isolates prior to the prescription of beta-lactam antibiotics is recommended. This could help prevent the spread of bacteria strains that are resistant to beta-lactam antibiotics.
authors.affiliation: Health Research Institute, Infectious and Tropical Diseases Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran; Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran.
authors.forename: Mojtaba
authors.initials: M
authors.lastname: Moosavian
authors.affiliation: Department of Microbiology, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, IR Iran.
authors.forename: Nazanin
authors.initials: N
authors.lastname: Ahmadkhosravy
keywords: CTX-M; Enterobacteriaceae; Extended-Spectrum Beta-Lactamase; Polymerase Chain Reaction