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Journal of Clinical Microbiology, August 2000, p. 2814-2818, Vol. 38, No. 8
Department of Pathology, The University of
Texas Health Science Center, San Antonio, Texas
782841; The Clinical Microbiology
Institute, Wilsonville, Oregon 970702; and
Department of Pathology, Washington University Medical
Center, St. Louis, Missouri 631103
Received 27 January 2000/Returned for modification 31 March
2000/Accepted 16 May 2000
The VITEK 2 is a new automated instrument for rapid organism
identification and susceptibility testing. It has the capability of
performing rapid susceptibility testing of Streptococcus
pneumoniae with specially configured cards that contain enriched
growth medium and antimicrobial agents relevant for this organism. The
present study compared the results of testing of a group of 53 challenge strains of pneumococci with known resistance properties and a collection of clinical isolates examined in two study phases with a
total of 402 and 416 isolates, respectively, with a prototype of the
VITEK 2. Testing was conducted in three geographically separate
laboratories; the challenge collection was tested by all three
laboratories, and the unique clinical isolates were tested separately
by the individual laboratories. The VITEK 2 results of tests with 10 antimicrobial agents were compared to the results generated by the
National Committee for Clinical Laboratory Standards reference broth
microdilution MIC test method. Excellent interlaboratory agreement was
observed with the challenge strains. The overall agreement within a
single twofold dilution of MICs defined by the VITEK 2 and reference
method with the clinical isolates was 96.3%, although there were a
number of off-scale MICs that could not be compared. The best agreement
with the clinical isolates was achieved with ofloxacin and
chloramphenicol (100%), and the lowest level of agreement among those
drugs with sufficient on-scale MICs occurred with
trimethoprim-sulfamethoxazole (89.7%). Overall there were 1.3% very
major, 6.6% minor, and no major interpretive category errors
encountered with the clinical isolates, although >80% of the minor
interpretive errors involved only a single log2 dilution
difference. The mean time for generation of susceptibility results with
the clinical isolates was 8.1 h. The VITEK 2 provided rapid,
reliable susceptibility category determinations with both the challenge
and clinical isolates examined in this study.
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Rapid Automated Antimicrobial Susceptibility
Testing of Streptococcus pneumoniae by Use of the bioMerieux
VITEK 2

*
Corresponding author. Mailing address: Department of
Pathology, University of Texas Health Science Center, 7703 Floyd Curl Dr., San Antonio, TX 78284-7750. Phone: (210) 567-4088. Fax: (210) 567-2367. E-mail: jorgensen{at}uthscsa.edu.
Present address: MRL Pharmaceutical Services, Reston, VA.
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