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Extended-spectrum beta-lactamases: frequency, risk factors, and outcomes
Allison E Einhorn1, Melinda M Neuhauser, David T Bearden
1Department of Pharmacy Practice, College of Pharmacy, University of Illinois at Chicago, 60612, USA.
Study Objective:
To determine epidemiologic factors of extended-spectrum beta-lactamase (ESBL)-producing Escherichia coli or Klebsiella pneumoniae in a nonoutbreak setting.
Design:
Retrospective analysis.
Setting:
University teaching hospital.
Patients:
Fifty-seven patients with cultures of presumed ESBL-producing (i.e., ceftazidime-resistant) E. coli or K. pneumoniae.
Interventions:
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.
Measurements And Main 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.
Conclusion:
In addition to known populations at risk, ambulatory patients with chronic conditions represent another patient population that may harbor ESBL-producing organisms.