Comparison of Rapid NFT system and conventional methods for identification of nonsaccharolytic gram-negative bacteria

Abstract

This study examined the Rapid NFT system (Analytab Products, Plainview, N.Y.) to determine its ability to accurately identify 229 clinical isolates of mostly nonsaccharolytic gram-negative rods. Identifications were classified by the following scheme: correct (corresponding to excellent, very good, good, or acceptable identification as listed in the code book); low discrimination (correct identification among a range of listed possibilities, with additional tests necessary for accurate identification); incorrect. Correct identification was considered correct to species and subspecies for all organisms except Alcaligenes faecalis and "Alcaligenes odorans"; "A. faecalis/odorans" was considered a correct response. By using these criteria, 71.6% of the strains were correctly identified, 17.9% were identified with low discrimination, and 10.5% were incorrectly identified. When consideration was made for incorrect identification resulting from taxonomic problems (e.g., Alcaligenes and Moraxella spp.), incorrect identifications fell to 5.2%. The Rapid NFT system was truly rapid and was easy to use and interpret. Its use of carbon substrate assimilation enables it to provide more accurate identification of medically important nonsaccharolytic bacteria than do other commercially available systems.