Identification of Enterobacteriaceae in Microtube Test Panels

Identification of Enterobacteriaceae can be accomplished efficiently and inexpensively by utilizing microtube technology. This report describes the composition of 18 different media developed for use in microdilution test panels. Tests with 453 previously identified stock cultures were performed in microtube trays and with the API-20E system. Only two (0.4%) of the 453 strains were misidentified with the API-20E system, and only three (0.7%) of the strains were misidentified with the microtube system. Both systems were considered to yield inconclusive results if the genus could not be confirmed without additional delay. With the API-20E system, 48 (10.6%) of the 453 strains gave inconclusive results, and the microtube trays yielded inconclusive results with 56 (12.4%) of the strains. We concluded that microdilution test panels can be used efficiently and inexpensively to identify most enteric bacilli with a reasonable degree of accuracy. As with most other identification systems, supplementary procedures are needed to confirm the identification of some strains.