ACCURACY OF THE VITEK SYSTEM FOR ANTIMICROBIAL SUSCEPTIBILITY TESTINGENTEROBACTERIACEAE BLOOD-STREAM INFECTION ISOLATES - USE OF DIRECT INOCULATION FROM BACTEC-9240 BLOOD CULTURE BOTTLES

A recent investigation indicates that rapid antimicrobial susceptibili ty tests (AST) can affect patient therapy lending to reductions in hea lth-care costs for some patient populations. However, there is little information relative to the often performed direct inoculation of posi tive blood culture bottles into rapid AST systems. AST results of dire ct inoculated Vitek (bioMerieux Vitek, Hazelwood, MO, USA) GNS cards w ere compared to those inoculated per package insert recommendations an d a reference broth microdilution test using 50 consecutive Enterobact eriaceae bloodstream infection isolates. Escherichia coil (44% of isol ates), Klebsiella ssp. (30%), and six other members of this family wer e tested against 15 antimicrobial agents. The direct inoculation metho d produced only two false-susceptible (0.3%), seven false-resistant (0 .9%; six different drugs), and 48 minor errors (6.4%). The GNS cards i noculated in the usual, recommended manner had no very major error, an d 7.5% combined major and minor errors. If the results of the urinary infection-specific drugs (nitrofurantoin, trimethoprim/sulfamethoxazol e; not appropriate for bacteremia therapy) and ampicillin/sulbactam we re deleted, both Vitek inoculation methods yielded results well within acceptable limits (less than or equal to 4.5% overall error). These r esults indicate that the direct inoculation method of Vitek GNS cards from Enterobacteriaceae bloodstream infections (detected by Bactec 924 0, Becton-Dickinson, Cockeysville, MD, USA) performed as well as the N CCLS broth microdilution test. Thus, a procedural modification of this type could further accelerate rapid access to accurate AST data. (C) 1997 Elsevier Science Inc.