title: Phenotypic and genotypic characterization of extended-spectrum b-lactamases producing Escherichia coli and Klebsiella pneumoniaein a tertiary care hospital in Riyadh, Saudi Arabia.
abstract: OBJECTIVE
  Extended-spectrum beta-lactamase (ESBL)-producing pathogens remain a public health concern, with limited data on the molecular characterization of isolates. We aimed to determine the molecular characterization of ESBL-producers circulating in our setting and correlate the molecular types with the minimal inhibitory concentration (MIC) to third-generation cephalosporins.
  
  
  METHODS
  Retrospective study conducted during the period from January to June 2013 at King Khalid University hospital, a tertiary-care hospital in Riyadh, Saudi Arabia.
  
  
  METHODS
  All Escherichia coli and Klebsiella pneumoniae confirmed to be ESBL producers were included. The MICs of ceftriaxone and ceftazidime were determined by the E-test. Molecular characterization of ESBL-genes was performed using the Check-MDR-CT102 DNA microarray.
  
  
  RESULTS
  Of 77 isolates comprising 50 (65%) E coli and 27 (35%) K pneumoniae, the majority (n=63; 81%) were from urine. Most isolates were blaCTX-M gene positive (n=72/77; 93.5%) comprising blaCTX-M1 (n=62), blaCTX-M9 (n=9) and blaCTX-M25 (n=1). Two or more ESBL genes were present in 45% of isolates with blaSHV predominating in K pneumoniae and blaTEM in E coli. Two isolates were positive for blaOXA-48 carried in combination with blaCTX-M9 and blaTEM in E coli and blaCTX-M1/CTX-M9 in K pneumoniae. Ceftriaxone MIC50 and MIC90 of >=256 micro g/mL were seen in E coli and K pneumoniae harboring blaCTX-M alone or in combination with blaSHV or blaTEM. For ceftazidime the highest MIC50 and MIC90 was seen in K pneumoniae harboring blaCTX-M+blaSHV and E coli with blaCTX-M+blaTEM combinations.
  
  
  CONCLUSIONS
  A preponderance of blaCTX-M suggests dissemination of the gene in our setting. The MIC for ceftriaxone and ceftazidime correlate well with molecular characterization of ESBL-producing Enterobacteriaceae.
authors.affiliation: Dr. Ali Mohammed Somily, Department of Pathology and Laboratory Medicine,, College of Medicine,, King Khaled University Hospital and King Saud University,, PO Box 2925, Riyadh 11461,, Saudi Arabia, T: 966-532-703-322, F: 966-11-467-9162, ali. somily@gmail.com.
authors.forename: Ali M
authors.initials: AM
authors.lastname: Somily
authors.forename: Muhammad Z
authors.initials: MZ
authors.lastname: Arshad
authors.forename: Ghada A
authors.initials: GA
authors.lastname: Garaween
authors.forename: Abiola C
authors.initials: AC
authors.lastname: Senok
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002442:Ceftazidime / Q000494:pharmacology; D002443:Ceftriaxone / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000302:isolation & purification*; D005260:Female; D005838:Genotype; D006785:Hospitals, University; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology / Q000302:isolation & purification*; D008297:Male; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D012189:Retrospective Studies; D012529:Saudi Arabia; D055815:Young Adult; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D002443:Ceftriaxone; D002442:Ceftazidime; D001618:beta-Lactamases