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Journal of Clinical Microbiology, September 2001, p. 3247-3253, Vol. 39, No. 9
Department of Microbiology, School of
Medicine,1 and University Hospital
Virgen Macarena,2 University of Seville,
Seville, Spain
Received 12 February 2001/Returned for modification 31 March
2001/Accepted 24 June 2001
VITEK 2 is a new automatic system for the identification and
susceptibility testing of the most clinically important bacteria. In
the present study 198 clinical isolates, including Pseudomonas aeruginosa (n = 146), Acinetobacter
baumannii (n = 25), and
Stenotrophomonas maltophilia (n = 27) were evaluated. Reference susceptibility testing of cefepime,
cefotaxime, ceftazidime, ciprofloxacin, gentamicin, imipenem,
meropenem, piperacillin, tobramycin, levofloxacin (only for P.
aeruginosa), co-trimoxazole (only for S.
maltophilia), and ampicillin-sulbactam and tetracycline (only
for A. baumannii) was performed by microdilution
(NCCLS guidelines). The VITEK 2 system correctly identified 91.6, 100, and 76% of P. aeruginosa, S.
maltophilia, and A. baumannii isolates,
respectively, within 3 h. The respective percentages of essential
agreement (to within 1 twofold dilution) for P.
aeruginosa and A. baumannii were 89.0 and 88.0%
(cefepime), 91.1 and 100% (cefotaxime), 95.2 and 96.0% (ceftazidime), 98.6 and 100% (ciprofloxacin), 88.4 and 100%
(gentamicin), 87.0 and 92.0% (imipenem), 85.0 and 88.0% (meropenem),
84.2 and 96.0% (piperacillin), and 97.3 and 80% (tobramycin). The
essential agreement for levofloxacin against P.
aeruginosa was 86.3%. The percentages of essential agreement
for ampicillin-sulbactam and tetracycline against A.
baumannii were 88.0 and 100%, respectively. Very major errors
for P. aeruginosa (resistant by the reference method,
susceptible with the VITEK 2 system [resistant to susceptible]) were
noted for cefepime (0.7%), cefotaxime (0.7%), gentamicin (0.7%),
imipenem (1.4%), levofloxacin (2.7%), and piperacillin (2.7%) and,
for one strain of A. baumannii, for imipenem. Major errors (susceptible to resistant) were noted only for
P. aeruginosa and cefepime (2.0%), ceftazidime (0.7%),
and piperacillin (3.4%). Minor errors ranged from 0.0% for
piperacillin to 22.6% for cefotaxime against P.
aeruginosa and from 0.0% for piperacillin and ciprofloxacin to
20.0% for cefepime against A. baumannii. The VITEK 2 system provided co-trimoxazole MICs only for S.
maltophilia; no very major or major errors were obtained
for co-trimoxazole against this species. It is concluded that the VITEK
2 system allows the rapid identification of S.
maltophilia and most P. aeruginosa and
A. baumannii isolates. The VITEK 2 system can
perform reliable susceptibility testing of many of the antimicrobial
agents used against P. aeruginosa and
A. baumannii. It would be desirable if new versions
of the VITEK 2 software were able to determine MICs and the
corresponding clinical categories of agents active against S.
maltophilia.
0095-1137/01/$04.00+0 DOI: 10.1128/JCM.39.9.3247-3253.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Evaluation of the VITEK 2 System for the Identification and
Susceptibility Testing of Three Species of Nonfermenting Gram-Negative
Rods Frequently Isolated from Clinical Samples
*
Corresponding author. Mailing address: Department of
Microbiology, School of Medicine, University of Seville, Apdo. 914, 41080 Seville, Spain. Phone: 34-95-500 8287. Fax: 34-95-437 7413. E-mail: lmartin{at}cica.es.
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