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Journal of Clinical Microbiology, 08 1997, 2061-2067, Vol 35, No. 8
CL Emery and LA Weymouth
The prevalence of extended-spectrum beta-lactamase (ESBL)-mediated
resistance remains unknown for most hospitals, and national guidelines for
testing and reporting ESBL-mediated resistance have not yet been developed.
We undertook a study to determine the prevalence of ESBLs and the clinical
need for testing in our tertiary-care medical center. Members of the family
Enterobacteriaceae isolated over a 6-month period for which ceftazidime or
ceftriaxone MICs were greater than 1 microg/ml were tested for production
of ESBLs by the double-disk synergy method. Approximately 1.5% of isolates
of the family Enterobacteriaceae (50 of 3,273), which were isolated from
1.2% of patients (23 of 1,844), were found to express ESBLs. ESBL-producing
strains included eight different species and were isolated from patients
located throughout the hospital, including outpatient clinics. By using the
interpretive guidelines of the National Committee for Clinical Laboratory
Standards, 26 to 39% of the isolates would have been reported to be
susceptible to ceftazidime, depending upon the routine susceptibility
method used. However, tests with cefpodoxime found all of the
ESBL-producing strains to be resistant or intermediate. Nine patients
infected with ESBL- producing isolates were treated with therapy which
included an expanded- spectrum cephalosporin. Seven were cured. The deaths
of the other two patients were not attributed to bacterial resistance
missed by routine susceptibility testing. These observations suggest that
in our tertiary- care medical center, it may not be clinically necessary or
cost- effective at this time to institute additional testing on a routine
basis to detect ESBL production in all clinical isolates of the family
Enterobacteriaceae.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Detection and clinical significance of extended-spectrum beta- lactamases in a tertiary-care medical center
Department of Pathology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298, USA.
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