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.

Factors affecting the value of a simple biochemical scheme for identifying Enterobacteriaceae: the reproducible recognition of biotypes.

“…The small and specific number of tests chosen was based on our experience of the relative occurrence of genera and species and designed to allow the simplest identification scheme for the Enterobacteriaceae commonly isolated in this laboratory. Other evidence shows that this distribution of isolates is not uncommon in other routine medical laboratories (Rosner, 1970;Berger and Einecke, 1973;Chadwick et al, 1974).…”

“…Many workers have described biochemical schemes for identifying Enterobacteriaceae (Carpenter et al, 1966;Rosner, 1970;Chadwick et al, 1974;Lassen, 1975) and several commercially available systems have been evaluated (Tomfohrde et al, 1973;Nord et al, 1975).…”

Activity of Netilmicin Compared with Those of Gentamicin and Tobramycin Against Enterobacteria and Pseudomonas aeruginosa

“…The 500 cultures were isolates from separate patients collected over a 4-month period. Enterobacteria were identified primarily by the replica plate method described by Chadwick et al (2) and by additional reactions in fluid media where necessary. P. aeruginosa isolates were identified by methods recommended by Cowan and Steel (3).…”

Variation in Metabolism of Biochemical Test Substrates by Klebsiella Species: An Epidemiological Tool

“…Klebsiella isolates differed in their ability to metabolise the majority of the 18 substrates examined (tables 11, I11 and IV). Quite different results were obtained with the two substrates, aesculin and inositol, that have been used in the primary isolation of klebsiellae (Davis and Matsen, 1974) and in their differentiation from other Enterobacteriaceae (Chadwick, Delisle and Byer, 1974;. The absence of variation in the ability to metabolise aesculin establishes the value of this substrate, but the presence of wide variations in metabolism of inositol, and the failure to detect the fermentation of inositol by many isolates from a normal working concentration (1 %, w/v) of substrate, emphasises the limitations associated with the use of inositol for the differentiation of various klebsiellae.…”