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Journal of Clinical Microbiology, October 2009, p. 3283-3288, Vol. 47, No. 10
0095-1137/09/$08.00+0     doi:10.1128/JCM.00505-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Validation of Vitek 2 Nonfermenting Gram-Negative Cards and Vitek 2 Version 4.02 Software for Identification and Antimicrobial Susceptibility Testing of Nonfermenting Gram-Negative Rods from Patients with Cystic Fibrosis{triangledown}

Ines Otto-Karg,1* Stefanie Jandl,1 Tobias Müller,1 Beate Stirzel,1 Matthias Frosch,1 Helge Hebestreit,2 and Marianne Abele-Horn1

Institute for Hygiene and Microbiology, University of Würzburg, Würzburg, Germany,1 Department of Pediatrics, University of Würzburg, Würzburg, Germany2

Received 12 March 2009/ Returned for modification 8 June 2009/ Accepted 18 August 2009

Accurate identification and antimicrobial susceptibility testing (AST) of nonfermenters from cystic fibrosis patients are essential for appropriate antimicrobial treatment. This study examined the ability of the newly designed Vitek 2 nonfermenting gram-negative card (NGNC) (new gram-negative identification card; bioMérieux, Marcy-l'Ètoile, France) to identify nonfermenting gram-negative rods from cystic fibrosis patients in comparison to reference methods and the accuracy of the new Vitek 2 version 4.02 software for AST compared to the broth microdilution method. Two hundred twenty-four strains for identification and 138 strains for AST were investigated. The Vitek 2 NGNC identified 211 (94.1%) of the nonfermenters correctly. Among morphologically atypical microorganisms, five strains were misidentified and eight strains were determined with low discrimination, requiring additional tests which raised the correct identification rate to 97.8%. Regarding AST, the overall essential agreement of Vitek 2 was 97.6%, and the overall categorical agreement was 92.9%. Minor errors were found in 5.1% of strains, and major and very major errors were found in 1.6% and 0.3% of strains, respectively. In conclusion, the Vitek NGNC appears to be a reliable method for identification of morphologically typical nonfermenters and is an improvement over the API NE system and the Vitek 2 GNC database version 4.01. However, classification in morphologically atypical nonfermenters must be interpreted with care to avoid misidentification. Moreover, the new Vitek 2 version 4.02 software showed good results for AST and is suitable for routine clinical use. More work is needed for the reliable testing of strains whose MICs are close to the breakpoints.

* Corresponding author. Mailing address: Bayerisches Landesamt für Gesundheit und Lebensmittelsicherheit, Eggenreuther Weg 43, D-91058 Erlangen, Würzburg, Germany. Phone: 49-(0)9131-764233. Fax: 49-(0)9131-764269. E-mail: ines.otto-karg{at}lgl.bayern.de

{triangledown} Published ahead of print on 26 August 2009.

Journal of Clinical Microbiology, October 2009, p. 3283-3288, Vol. 47, No. 10
0095-1137/09/$08.00+0     doi:10.1128/JCM.00505-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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