EVALUATION OF 2 BBL CRYSTAL SYSTEMS FOR IDENTIFICATION OF SOME CLINICALLY IMPORTANT GRAM-NEGATIVE BACTERIA

The BBL Crystal system (Becton Dickinson Microbiology Systems, Cockeys ville, Md.) is a miniaturized bacterial identification method employin g modified conventional and chromogenic substrates. Two products are c urrently available, the Rapid Stool/Enteric ID Kit and the Enteric/Non fermenter ID Kit, each comprising thirty tests. We report an evaluatio n of both systems (using database version 1.1 for both) in the identif ication of 51 gram-negative taxa likely to be encountered commonly in the clinical laboratory. In all, 266 strains were tested in the Enteri c/Nonfermenter ID Kit, and these represented 36 taxa of the family Ent erobacteriaceae (188 strains), 5 oxidase-positive fermentative taxa (2 6 strains), and 10 nonfermentative taxa (52 strains). The majority of these same strains (203 of 266) were also tested in the Rapid Stool/En teric ID Kit. The Enteric/Nonfermenter ID Kit performed as follows: En terobacteriaceae, 93% correct, 6% not identified, and 1% incorrect; ox idase-positive fermenters, 88, 12, and 0%, respectively; and nonfermen ters, 100% correct, although several only to the genus or group level. The Rapid Stool/Enteric ID Kit gave the following results: Enterobact eriaceae, 91% correct, 7% not identified, and 2% incorrect; oxidase-po sitive fermenters, 80, 13, and 7%, respectively (but results were base d on only 15 strains); and nonfermenters, 100% correct (but results we re based on only 11 strains). We found the systems extremely easy and rapid to use, and for the Enteric/Nonfermenter ID Kit an identificatio n rate of 100% in 40 of 51 taxa was achieved, with corresponding figur es of 29 of 39 taxa for the Rapid Stool/Enteric ID Kit.