EVALUATION OF BIOLOG SYSTEM FOR IDENTIFICATION OF SOME GRAM-NEGATIVE BACTERIA OF CLINICAL IMPORTANCE

The Biolog system (Biolog, Inc., Hayward, Calif) was evaluated for the identification of 55 gram-negative taxa (789 strains) likely to be en countered commonly in clinical laboratories. The Biolog system perform ed best with oxidase-positive fermenters and biochemically active nonf ermenters and had the most problems with unreactive nonfermenters. It gave significantly better results when the MicroPlates were read manua lly rather than when they were read by the automated reader. Plates re ad manually gave the following performances: oxidase-positive fermente rs, five taxa, 64 strains, 92% correct, 3% not identified, and 5% inco rrect; biochemically active nonfermenters, eight taxa, 122 strains, 88 % correct, 6% not identified, and 6% incorrect; members of the family Enterobacteriaceae, 35 taxa, 511 strains, 77% correct, 8% not identifi ed, and 15% incorrect; unreactive nonfermenters, seven taxa, 92 strain s, 38% correct, 24% not identified, and 38% incorrect. We found the sy stem easy to use, but while for 39 of 55 of the taxa an identification rate of >70% was achieved, problems were encountered, particularly wi th identification of capsulated strains of some Enterobacter and Klebs iella taxa, as well as the least biochemically active Moraxella and Ne isseria strains.