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Validation of VITEK 2 GN Cards and VITEK 2 Version 4.02 Software for identification and antimicrobial susceptibility testing of nonfermenting Gram-negative bacilli from cystic fibrosis patients

Abstract number: 1733_1215

Otto-Karg I.M., Jandl S., Müller T., Stirzel B., Vogel U., Frosch M., Hebestreit H., Abele-Horn M.

Objectives: Accurate identification (ID) and antimicrobial susceptibility (AST) testing of bacterial isolates from cystic fibrosis (CF) patients is known to pose problems. Commercially automated test systems are available, but have not been recommended so far. Aim of this study was to evaluate the VITEK 2 GN card for ID and the new VITEK 2 version 4.02 software for AST of nonfermenting Gram-negative bacilli from CF-patients compared to reference methods.

Methods: A total of 168 strains for ID and 117 strains for AST were investigated. Clinical isolates from CF-patients were identified with the VITEK 2 GN card and with the API NE system. If ID results differed, molecular methods were used for definitive identification. Broth microdilution method served as reference method for AST against nine antibiotic agents including cefepime, ceftazidime, piperacillin, imipenem, meropenem, gentamicn, tobramycin, ciprofloxacin, and cotrimoxazole. Interpretation of the AST results was performed according to the DIN 58940 standard.

Results: Of the 168 strains tested 143 yielded concordant results. The discordant 25 strains underwent 16S rRNA gene sequencing. The VITEK 2 GN card identified 12 of 25 strains correctly to the species level (155/168, 92%) and nine strains correctly to the genus level (164/168; 98%); 4 (2%) strains were misidentified. In contrast, the API NE correctly identified 4 of those strains to species level (147/168; 88%), 9 strains to genus level (154/168; 93%) and misidentified 12 (7%) strains. Regarding AST, overall categorical agreement of VITEK 2 compared to the reference method was 97% for all antibiotics. Minor errors were found in 8%.

Conclusion: The new VITEK 2 GN card appears to be a reliable method for identification of nonfermenting Gram-negative bacilli from CF patients. Moreover, the new VITEK 2 version 4.02 software showed good results when compared to reference method for AST and appears to be applicable for routine clinical use in AST of nonfermenting Gram-negative bacilli of CF patients.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Subject:
Location: ICC, Munich, Germany
Presentation type:
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