Use of the Autobac IDX system for rapid identification of Enterobacteriaceae and nonfermentative gram-negative bacilli

Abstract

The Autobac IDX system was evaluated for its ability to accurately identify 290 gram-negative bacilli from 18 different genera. Excluding isolates with a low identification probability, the overall sensitivity of the system was found to be 95.8%. Late lactose-fermenting Escherichia coli, Citrobacter freundii, and Proteus mirabilis accounted for over 90% of the misidentifications. The Autobac IDX system offers a rapid and reliable method for the identification of gram-negative bacilli. An increased emphasis has been placed on the rapid identification and susceptibility testing of microorganisms. To this end, the Autobac system (General Diagnostics, Warner-Lambert Co., Morris Plains, N.J.) was introduced for rapid susceptibility testing of bacteria (6). Subsequently, the Autobac system was adapted for determination of minimum inhibitory concentrations (4), urine screening (3), and more recently for testing salt tolerance of streptococci (2). Additionally, the Autobac system has recently been updated and modified to include bacterial identification capabilities. Along with rapid identification of Enterobacteriaceae, the system has also been reported to rapidly identify nonfermentative gram-negative bacilli. Early reports delineating the data base indicated 88.4% (7) and 95.3% (1) agreement with conventional biochemical identification. Two recent reports have substantiated the accuracy of the Autobac identification system (N. M.

Comparison of the Quantum II Bacterial Identification System and the AutoMicrobic System for the identification of gram-negative bacilli

“…Although the conventional macrotube methods of bacterial identification are still used in microbiology laboratories, the state of the art is the systems approach to identification with emphasis on standardization, speed, reproducibility, and in the last several years, mechanization and automation (1,3,4,(6)(7)(8)(14)(15)(16)(17). Thus, the conventional methods have been adapted or streamlined into miniaturized test systems which use numerical coding systems, computer-generated data bases, and reaction endpoints which can be reached after 4 to 6 h of incubation (1, 3, 4, 6-8, [14][15][16][17].…”

“…Several of the commercial systems currently available are potentially subject to reader bias despite offering a variety of biochemical tests, systematic coding systems, and broad computer-generated data bases (7). Fortunately, this problem has largely been circumvented with the development of microprocessor-based instrumentation which can both read and interpret tests in an identification system, thus providing excellent standardization, accuracy, and reproducibility (4,6,7,(14)(15)(16)(17)(18)24).…”

“…Although there are several large automated or semiautomated systems available for bacterial identification (4,6,8,(14)(15)(16)(17), these instruments frequently do not fulfill the needs of smaller laboratories, many of which would benefit from automated test reading and interpretation but do not have the necessary laboratory space or funds. The recently introduced Quantum II Bacterial Identification System (BID; Abbott Laboratories, Irving, Tex.)…”

Automated systems for identification of microorganisms.

“…Shulman et al (105) reported on the ability of the ALA-DIN to read UniScept 20E panels. A total of 300 isolates (144 E. coli, 45 Proteus/Providencia spp., 27 KiebsiellalEnterobacter spp., 18 Serratia spp., 12 Pseudomonas spp., and 54 other organisms) were tested. On a test-for-test basis, the ALADIN and visual readings of 300 organisms showed a 99.0% level of correlation.…”

“…In summary, early studies with the Autobac Series II demonstrated that most of the gram-negative bacilli commonly isolated in the clinical laboratory were correctly identified (10,11,18,27,60,106,111). However, problems were reported in the identification of such organisms as Enterobacter cloacae, C. freundii, Proteus vulgaris, Providencia spp., Salmonella spp., Shigella spp., P. cepacia, and many uncommon organisms.…”