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Journal of Clinical Microbiology, January 2001, p. 241-250, Vol. 39, No. 1
Hospital Infections Program, Centers for Disease Control
and Prevention,1 and World Health
Organization Collaborating Center for Global Antimicrobial
Resistance Monitoring,2 Atlanta, Georgia 30333;
World Health Organization, Geneva,
Switzerland3; and World Health
Organization Collaborating Center for Surveillance of Antimicrobial
Resistance, Brigham and Women's Hospital, Boston, Massachusetts
021154
Received 17 February 2000/Returned for modification 18 April
2000/Accepted 4 October 2000
The accuracy of antimicrobial susceptibility data submitted by
microbiology laboratories to national and international surveillance systems has been debated for a number of years. To assess the accuracy
of data submitted to the World Health Organization by users of the
WHONET software, the Centers for Disease Control and
Prevention distributed six bacterial isolates representing key
antimicrobial-resistance phenotypes to approximately 130 laboratories, all but one of which were outside of the United States, for
antimicrobial susceptibility testing as part of the World Health
Organization's External Quality Assurance System for Antimicrobial
Susceptibility Testing. Each laboratory also was asked to submit 10 consecutive quality control values for several key organism-drug
combinations. Most laboratories were able to detect methicillin
(oxacillin) resistance in Staphylococcus aureus, high-level
vancomycin resistance in Enterococcus faecium, and
resistance to extended-spectrum cephalosporins in Klebsiella
pneumoniae. Many laboratories, particularly those using disk
diffusion tests, had difficulty in recognizing reduced susceptibility
to penicillin in an isolate of Streptococcus pneumoniae. The most difficult phenotype for laboratories to detect was reduced susceptibility to vancomycin in an isolate of Staphylococcus
epidermidis. The proficiency testing challenge also included a
request for biochemical identification of a gram-negative bacillus,
which most laboratories recognized as Enterobacter cloacae.
Although only a small subset of laboratories have submitted their
quality control data, it is clear that many of these laboratories
generate disk diffusion results for oxacillin when testing S. aureus ATCC 25923 and S. pneumoniae ATCC 49619 that
are outside of the acceptable quality control range. The narrow quality
control range for vancomycin also proved to be a challenge for many of
the laboratories submitting data; approximately 27% of results were
out of range. Thus, it is important to establish the proficiency of
laboratories submitting data to surveillance systems in which the
organisms are tested locally, particularly for penicillin resistance in
pneumococci and glycopeptide resistance in staphylococci.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.1.241-250.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Ability of Laboratories To Detect Emerging Antimicrobial
Resistance: Proficiency Testing and Quality Control Results from the
World Health Organization's External Quality Assurance System for
Antimicrobial Susceptibility Testing
*
Corresponding author. Mailing address: Nosocomial
Pathogens Laboratory Branch (G-08), Centers for Disease Control and
Prevention, 1600 Clifton Road, NE, Atlanta, GA 30333. Phone: (404)
639-3246. Fax: (404) 639-1381. E-mail: fnt1{at}cdc.gov.
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