Identification of Enterobacteriaceae in frozen microdilution trays prepared by Micro-Media Systems.

Frozen microdilution trays, with 20 different biochemical test media for identification of Enterobactericeae, were evaluated. The test panels were those provided by Micro-Media Systems (MMS), who also provided a code book for interpretation of the test results. The interpretations of the MMS test system and of the Analytab API 20E test system were compared with those obtained from tests with conventional media. Tests with 468 Enterobacteriaceae demonstrated nearly comparable results with the two commercial systems. About 6% (API) and 7% (MMS) of the isolates could not be identified without additional tests, and another 3% (MMS) to 4% (API) of the isolates gave test patterns that were not found in the code books. One to three percent of the isolates were misidentified. It was concluded that the MMS Enteric Quad Panels provide an efficient, relatively inexpensive, and reasonably accurate method for identification of the Enterobacteriaceae.