A recently published paper in the Journal of Clinical Microbiology describes an evaluation of the bioMerieux VITEK 2 card for gram-negative bacteria which has been redesigned to improve the identification of fermenting and nonfermenting bacilli.

Forty-seven biochemical tests, including 19 enzymatic tests, are present in the new card and interpreted in a kinetic mode. Final identification results are available within 10 h. The database allows the identification of 159 different taxa.

Six hundred fifty-five gram-negative rods (511 fermenters and 144 nonfermenters), representing 54 taxa, were tested. Strains were taken from fresh routine primary isolation plates (157 strains), from stored routine plates (301 strains), and from stock cultures (197 strains).

Six hundred thirty-seven strains (97.3%) were correctly identified to the species level, 14 strains (2.1%) gave low discrimination results requiring additional tests, and 4 strains (0.6%) gave discordant results; not a single strain remained unidentified. Nearly 92% of all isolates were correctly identified within 7 h of incubation.

The robustness of the system was demonstrated by the fact that strains were grown on four different agar media before testing. The system may also have the potential to be applied directly to primary isolation plates, since in this instance 96.2% of 157 gram-negative rods were correctly identified and 3.8% gave low discrimination results. The authors report the new VITEK 2 card for gram-negative bacteria to be a promising new tool for routine, rapid identification of GNR.

Reference:
Journal of Clinical Microbiology, September 2004, p. 4067-4071, Vol. 42, No. 9