Evaluation of two rapid methods for identification of commonly encountered nonfermenting or oxidase-positive, Gram-negative rods

Abstract

The ability of the expanded API-20E and the Oxi-Ferm System to identify 176 isolates of nonfermenting or oxidase-positive, gram-negative rods from 17 species or groups was studied. The expanded API-20E, without referral to a computer reference center, was able to identify 61.4% of the isolates to the species level. If reference to the computer center was utilized, an additional 25% could be identified. Of the isolates examined, 13.6% were misidentified, partially identified, or assigned no identification. Those assigned to the incorrect genus constituted 0.5% of the isolates tested; those assigned to the correct genus, but the wrong species, constituted 0.5%; 4.5% were placed in the correct genus with no species given; and 7.9% were assigned no identification. The Oxi-Ferm System was able to assign 75% of the isolates to the correct species without further testing, and an additional 19.3% required additional testing for correct identification. Those assigned to the incorrect genus represented 3.4% of the isolates tested; 1.1% were assinged to the correct genus, but the wrong species; and 1.1% were assigned to the correct genus, with no species indicated.