Reproducibility of three microdilution systems for identification of enterobacteriaceae, compared with API 20E and micro-ID test systems

Abstract

Five systems for identifying Enterobacteriaceae were evaluated in terms of their ability to provide reproducible results. Frozen microdilution panels (Micro-Media Systems), prepared media ready for dispensing into microdilution trays (Dynatech laboratories), media prepared in our laboratories and dispensed into microdilution trays (UC media), the Micro-ID system (General Diagnostics), and the API 20E system (Analytab Products, Inc.) were all evaluated. Fifty selected isolates were tested with each system on three separate days. Although biotypes were some-what variable, the final identification was rarely affected. The API 20E system was the most variable and microdilution tests, with UC media, were the least variable. Precision of tests performed in microdilution trays was as good, if not better than, that obtained with the other two commercial products (Micro-ID and API 20E).