Validation of the VITEK2 and the Advance Expert System with a collection of Enterobacteriaceae harboring extended spectrum or inhibitor resistant beta-lactamases.
The susceptibility testing accuracy of the VITEK2 system and the ability of the Advance Expert System (AES) to provide interpretive readings were evaluated against 86 extended spectrum (ESBL) and 6 inhibitor-resistant-TEM (IRT) beta-lactamases producing Enterobacteriaceae clinical isolates. VITEK2 MICs of 12 beta-lactams were compared with those obtained by the standard NCCLS microdilution technique. The overall essential agreement ( +/- 1 log dilution) was 87.8%. Discrepancies were mainly observed with cefepime (30.3% of total number of discrepancies), ceftazidime (21.2%), and cefotaxime (15.1%). MIC discrepancies were slightly higher in CTX-M- (14.4%) than in TEM- (12.5%) or SHV- (11.9%) type ESBL producers and were rare in IRT producers (1.4%). Overall interpretive agreement was 92.5% and minor, major, and very major errors were 5.4%, 1.7%, and 2.1%, respectively. The AES was able to identify an ESBL phenotype in 85 out of 86 isolates (98.8%) and an IRT phenotype in all 6 isolates harboring these enzymes, thus reducing very major errors to 0.9%. The VITEK2 system, in conjunction with the AES software, is a reliable tool for detection of ESBL or IRT producing Enterobacteriaceae isolates.
Cantón
R
R
Servicio de Microbiología, Hospital Ramón y Cajal, Madrid, Spain. rcanton@hrc.insalud.es
Pérez-Vázquez
M
M
Oliver
A
A
Coque
T M
TM
Loza
E
E
Ponz
F
F
Baquero
F
F
D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology; D005103:Expert Systems; D008826:Microbial Sensitivity Tests; D018440:beta-Lactam Resistance; D001618:beta-Lactamases; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D047090:beta-Lactams; D001618:beta-Lactamases