r-b Expanders: their use in identifying routinely and unusually reacting members of Enterobacteriaceae

Biochemical characteristics and identification of Enterobacteriaceae isolated from meats

The isolation and identification of 2,220 Enterobacteriaceae from meats indicated that Escherichia coli biotype I, Enterobacter agglomerans, and Serratia liquefaciens were the principal types to be differentiated in meats. Citrobacter freundii, Klebsiella pneumoniae, Enterobacter cloacae, and Enterobacter hafniae were also commonly identified. Identification of isolates by the Encise II (Roche Diagnostics Inc., Nutley, N.J.) and Minitek (BBL Microbiology Systems, Cockeysville, Md.) coding systems gave similar results with only 255 (11.5%) discrepancies in identity, but both systems required large numbers of supplementary tests for identification of the isolates. Not only the distribution of Enterobacteriaceae types isolated from meats but also some of the biochemical reactions of the isolates differed from those of clinical isolates. The Minitek technique is recommended because of its versatility. However, with the addition of cellobiose and salicin disks and the inclusion of methyl red to the Minitek test and the use of the Voges-Proskauer test and gas production in EC medium at elevated temperature as standard tests, the identification of these Enterobacteriaceae from meats would be greatly facilitated. The inclusion of the motility test, for example, using nitrate motility agar, would also be of value to Enterobacteriaceae identification.

Simplified scheme for identification of prompt lactose-fermenting members of the Enterobacteriaceae

A brief, simplified scheme involving the spot indole test and colonial morphology was evaluated for genus level identification of prompt lactose-fermenting (PLF) members of the Enterobacteriaceae. One hundred and ninety-four consecutive, clinically important PLF gram-negative rods isolated in a clinical microbiology laboratory were identified by this simplified scheme, as well as by standard biochemical tests, and the API 20E (Analytab Products, Inc., Plainview, N.Y.) system. In the simplified scheme a flat, spot indole-positive colony was identified as Escherichia coli. Spot indole-negative organisms forming nucoid colonies were identified as Klebsiella sp. or Enterobacter sp. on the basis of semisolid motility and ornithine decarboxylase tests. Approximately 94% of the study isolates followed reactions typical for E. coli, Klebsiella sp., and Enterobacter sp. as defined by this simplified scheme. When compared with the standard and Analytab Products Inc. identifications, the overall accuracy was 97.4%. The accuracy of identification of E. coli, Klebsiella sp., and Enterobacter sp. was 98.1%, 95.6%, and 87.5%, respectively. This simplified scheme is recommended for identification of selected PLF isolates in the clinical microbiology laboratory.

Evaluation of the Enteric Analyzer, an instrument to aid in the identification of Enterobacteriaceae

This study evaluated the Enteric Analyzer, an instrument designed to identify Enterobacteriaceae, with data obtained from the Modified r/b Enteric Differential System, other rapid identification systems, or conventional identification systems. It is programmed for 19 reactions with data obtained from Center for Disease Control publications. The instrument is very simple to use. Typical strains from 25 of 28 species were unequivocally identified. With the other three species, two choices were given. A switch allows the user to identify all species possibilities where a given biochemical pattern occurs in more than 1% of the strains or more than 10% of the strains. The instrument is useful both in the clinical laboratory and for teaching purposes.

Clinical laboratory evaluation of the further improved Enterotube and Encise II

The most recent improvements in the Enterotube coupled with Encise II permitted identification of routinely and abnormally reacting members of the family Enterobacteriaceae.

Re-evaluation of the Auxotab (Inolex) Enteric 1 System for identification of enterobacteriaceae

The improved Auxotab Enteric I System was re-evaluated and found to correlate 98% with conventional methods for the identification of Enterobacteriaceae. Possible Reasons for previous poor results with this system are discussed.

Evaluation of the R/B and Minitek systems for identification of Enterobacteriaceae

The R/B and Minitek systems for the identification of Enterobacteriaceae were evaluated, and the results were compared with those obtained by conventional methods. Both systems were rapid and allowed correct identification of about 85% of the 294 isolates (23 species) examined. The individual biochemical reactions showed an overall agreement of 92.6% and 93.1% for the R/B and Minitek systems, respectively.