Affiliation:
1. Department of Microbiology, School of Medicine,1 and
2. University Hospital Virgen Macarena,2 University of Seville, Seville, Spain
Abstract
ABSTRACT
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
.
Publisher
American Society for Microbiology
Cited by
80 articles.
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