Biochemical identification of hospital enterobacteria by replica agar plating

Abstract

An identification system was developed for enterobacteria isolated frequently from hospital patients, involving a set of biochemical reactions on agar media. The media were inoculated by a replication apparatus also used for setting up antibiotic sensitivity tests. Cultures in a control series showed a close correlation between reactions on the agar media and classical tests in a fluid medium. Of a series of 2668 laboratory isolates of enterobacteria, 2292 were identified outright by the selected reactions, 160 required one further test, and 216 could be identified only after repeating the reactions or the performance of additional tests. The identification has the advantages of speed, economy, and simplicity and is recommended for hospital laboratories handling large numbers of enterobacterial cultures.