Comparison of three methods for identifying nonfermenting gram-negative rods

Seventy-six strains of nonfermenting gram-negative rods were tested on the Analytab Products, Inc. (API) system and on conventional media. In addition, 51 strains were tested on the Oxi-Ferm system. When the identification results were compared, the API agreed with the conventional system on 41% of the isolates and Oxi-Ferm agreed with the conventional system on 72% of the isolates. API had the greatest difficulty in identifying Pseudomonas aeruginosa. API and Oxi-Ferm both had difficulty identifying P. cepacia. Oxi-Ferm had more individual discrepant biochemical reactions than did API when compared to the conventional media, but still maintained a higher percentage agreement with the conventional system.