Comparison of the API 20E and Oxi/Ferm systems in identification of nonfermentative and oxidase-positive fermentative bacteria

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Abstract
The API 2OE and Oxi/Ferm systems were tested in parallel to identify nonfermentative bacteria and oxidase-positive fermentative bacteria. Test strains consisted of consecutive clinical isolates, with stock cultures used to supplement those species infrequently recovered. The 2 microsystems and tubes of triple sugar iron, motility, cetrimide and oxidative glucose media were inoculated for each organism. Identification of each isolate was by the protocol of the manufacturers, with supplemental tests and flagella strains performed when necessary. Concurrent identification was undertaken with a conventional system against which the results of the 2 systems were compared for accuracy. There was a 95.3% accuracy in identification by the Oxi/Ferm system and 88.9% by the API system. Almost 1/4 of all identification attempts with the API required computer assistance and most of these were for oxidase-positive bacteria. Because of this, and because the API system showed greater accuracy in identification of the oxidase-negative bacteria, it seems best suited for identification of these organisms (Pseudomonas maltophilia, Acinetobacter anitratum, and A. lwoffi). The Oxi/Ferm system is technically less cumbersome than the API and is well suited for both groups of organisms.