title: Extended-spectrum beta-lactamases: frequency, risk factors, and outcomes.
abstract: OBJECTIVE
  To determine epidemiologic factors of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli or Klebsiella pneumoniae in a nonoutbreak setting.
  
  
  METHODS
  Retrospective analysis.
  
  
  METHODS
  University teaching hospital.
  
  
  METHODS
  Fifty-seven patients with cultures of presumed ESBL-producing (i.e., ceftazidime-resistant) E. coli or K. pneumoniae.
  
  
  METHODS
  To determine overall frequency, institutional antibiograms from 1991-1999 were examined for percentage of isolates with ceftazidime resistance. Medical records from January 1997-June 2000 were reviewed for patient demographics, comorbidities, culture site, antimicrobial therapy, and clinical and microbiologic outcomes.
  
  
  RESULTS
  From 1991-1999, frequency increased from undetectable to 4% for ceftazidime-resistant E. coli and from 2% to 6% for ceftazidime-resistant K. pneumoniae. Seventy-one isolates were identified in the 57 patients with presumed ESBL-producing E. coli or K. pneumonia. Fifty-one isolates (72%) were E. coli, with urine the primary site of infection (62%). Eighty-six percent of patients had known risk factors for infection due to ESBL-producing organisms, including hospitalization (37 patients) and residence in long-term care facilities (12 patients). However, in 14% (8 patients), the infection was community acquired in patients who resided at home.
  
  
  CONCLUSIONS
  In addition to known populations at risk, ambulatory patients with chronic conditions represent another patient population that may harbor ESBL-producing organisms.
authors.affiliation: Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, 60612, USA.
authors.forename: Allison E
authors.initials: AE
authors.lastname: Einhorn
authors.forename: Melinda M
authors.initials: MM
authors.lastname: Neuhauser
authors.forename: David T
authors.initials: DT
authors.lastname: Bearden
authors.forename: John P
authors.initials: JP
authors.lastname: Quinn
authors.forename: Susan L
authors.initials: SL
authors.lastname: Pendland
mesh_terms: D002442:Ceftazidime / Q000627:therapeutic use*; D002511:Cephalosporins / Q000627:therapeutic use*; D002641:Chicago / Q000453:epidemiology; D004352:Drug Resistance, Microbial; D004359:Drug Therapy, Combination / Q000627:therapeutic use*; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D005260:Female; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy* / Q000453:epidemiology / Q000382:microbiology; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D014505:Urban Population; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D002511:Cephalosporins; D002442:Ceftazidime; D001618:beta-Lactamases