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Journal of Clinical Microbiology, June 2000, p. 2108-2111, Vol. 38, No. 6
Servicio de Microbiología, Hospital
General Universitario "Gregorio Marañón," Madrid, Spain
Received 3 January 2000/Returned for modification 2 February
2000/Accepted 9 March 2000
We evaluated the new automated VITEK 2 system (bioMérieux)
for the identification and antimicrobial susceptibility testing of
enterococci. The results obtained with the VITEK 2 system were compared
to those obtained by reference methods: standard identification by the
scheme of Facklam and Sahm [R. R. Facklam and D. F. Sahm, p.
308-314, in P. R. Murray et al., ed., Manual of
Clinical Microbiology, 6th ed., 1995] and with the API 20 STREP
system and, for antimicrobial susceptibility testing, broth
microdilution and agar dilution methods by the procedures of the
National Committee for Clinical Laboratory Standards. The presence of
vanA and vanB genes was determined by PCR. A
total of 150 clinical isolates were studied, corresponding to 60 Enterococcus faecalis, 55 Enterococcus faecium, 26 Enterococcus gallinarum, 5 Enterococcus
avium, 2 Enterococcus durans, and 2 Enterococcus raffinosus isolates. Among those isolates, 131 (87%) were correctly identified to the species level with the VITEK 2 system. Approximately half of the misidentifications were for E. faecium with low-level resistance to vancomycin, identified as
E. gallinarum or E. casseliflavus; however, a
motility test solved the discrepancies and increased the agreement to
94%. Among the strains studied, 66% were vancomycin resistant (57 VanA, 16 VanB, and 26 VanC strains), 23% were ampicillin resistant
(MICs,
0095-1137/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Evaluation of a New System, VITEK 2, for
Identification and Antimicrobial Susceptibility Testing of
Enterococci
16 µg/ml), 31% were high-level gentamicin resistant, and
45% were high-level streptomycin resistant. Percentages of agreement for susceptibility and resistance to ampicillin, vancomycin, and teicoplanin and for high-level gentamicin resistance and high-level streptomycin resistance were 93, 95, 97, 97, and 96%, respectively. The accuracy of identification and antimicrobial susceptibility testing
of enterococci with the VITEK 2 system, together with the significant
reduction in handling time, will have a positive impact on the work
flow of the clinical microbiology laboratory.
*
Corresponding author. Mailing address: Servicio de
Microbiología, Hospital General Universitario "Gregorio
Marañón," Dr. Esquerdo 46, 28007 Madrid, Spain. Phone:
34-91-586-8459. Fax: 34-91-504-4906. E-mail:
fgarrote{at}efd.net.
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