BRIEF TECHNICAL REPORTS zyxwvutsrqp Evaluation of Crystal'" Rapid Stool/Enteric ID System for Identification of Aerobic Gram-negative Bacilli zy Alvaro Pascual, Maria J Clavijo, Maria D. Garcia-Perea, Luis Martinez-Martinez. Objective: zyxwvutsrqpo The evaluation of the new miniaturized Crystal'" Rapid Stool/Enteric System (Becton-Dickinson, USA) for identification of aerobic gram-negative bacilli. Methods: a total of 154 clinical organisms zyxwvutsrq (Enterobacteriaceae: 120 strains; oxidase-positive fermenters: 13 strains; non- fermenters: 21 strains) were tested. Results were compared with those obtained with the PASCORsystem (Difco, USA) and divergent identifications were evaluated by standard biochemical tests. Results: without additional testing, correct identification was obtained for 146 strains (Enterobacteriaceae: 95%; oxidase-positive fermenters 87%; non-fermenters 100%). For adequate identification of Yersinia enterocolitica strains, however, panels had to be incubated for 5 instead of 3 hours. Conclusions: the Crystal'" Rapid Stool/Enteric system offers a safe, accurate and rapid method for the identification of frequent isolates of the family Enterobacteriaceae and bacterial stool pathogens. zyxwvu There are several commercially available methods for identification of aerobic gram-negative rods (1). Most of them, however, require incubation periods of 18-24 hours to obtain definitive results. It could be useful to have systems allowing rapid identification of these microorganisms. The CrystalTM Rapid Stool/Enteric Identification System (CrystalTM RYE) is a minia- turized method employing modified conventional and chromogenic substrates intended for the identi- fication of enterobacteria and most stool pathogens in 3 hours (2, zyxwvutsrqpo 3). The purpose of this study was to compare the CrystalTM RS/E and PASCOR systems for the identification of aerobic gram-negative bacteria isolated from clinical specimens. Material and Methods University Hospital V. Macarena, Seville (Spain), were studied (Table 1). Organisms were identified by the PASCOR system (panel type 4G; Difco, USA) accord- ing to the manufacturer's instructions. The inoculum was prepared by using the PROMPTR system (Baxter, USA). Panels were incubated at 35°C for 18-20 hours. Identification was established according to the PASCOR data base. Oxidase tests were performed using the DrySlideTM system (Difco). CrystalTM RS/E panels were inoculated following the manufacturer's guidelines. The system contains 30 dry biochemical and enzimatic substrates. A bacterial suspension in CrystalTM RS/E ID inoculum fluid (equivalent to the McFarland 0.5-1 standards) obtained from colonies grown on Columbia agar supplemented with 5% sheep blood (BioMkrieux, France) was used to inoculate the panels which were hermetically closed and incubated for 3 hours at 35OC. In the case of Yersinia enterocolitica, panels were read again after 2 additional hours of incubation. Inoculum purity was always assessed. After incubation, tests were visually interpreted according to the crystay RS/E identi- fication color chart and a O-digit profile number was obtained for each isolate. Oxidase and indole (spot method) tests were always performed. Identi- fication was established according to the CrystalTM ID System Electronic Codebook. When discrepancies were observed the reference identification was obtained by standard methods zyxwv (4). One hundred and fifty four aerobic gram-negative bacteria isolated from blood cultures or stool speci- mens at the Clinical Microbiology Laboratory of the Alvaro Pascual, Maria J. Clavijo, Maria zyxwvutsrq D. Garcia-Perea, Luis Martinez-Martinez: Department of Microbiology, University Hospital V. Macarena, Avda. Dr. Fedriani s/n., Sevilla 41009, Spain. Corresponding author and reprint requests: Dr A. Pascual. Tel: (34) 5 455 7448 Fax: (34) 5 437 7413 This study was partially presented at the 7th European Congress of Clinical Microbiology and Vienna, Austria, March 1995. Diseases, 48