API-20E

 

An Introduction to
Bacterial Identification

Page 2: The API-20E® Enteric
Identification System

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BACTERIAL IDENTIFICATION:

• Page 1 – General Principles
• Page 2 – API-20E Enteric ID System
• Page 3 – Genotypic Identification


The API-20E test kit for the identification of enteric bacteria (bioMerieux, Inc., Hazelwood, MO) provides an easy way to inoculate and read tests relevant to members of the Family Enterobacteriaceae and associated organisms. A plastic strip holding twenty mini-test tubes is inoculated with a saline suspension of a pure culture (as per manufacturer's directions). This process also rehydrates the dessicated medium in each tube. A few tubes are completely filled (CIT, VP and GEL as seen in the photos below), and some tubes are overlaid with mineral oil such that anaerobic reactions can be carried out (ADH, LDC, ODC, H2S, URE).

After incubation in a humidity chamber for 18-24 hours at 37°C, the color reactions are read (some with the aid of added reagents), and the reactions (plus the oxidase reaction done separately) are converted to a seven-digit code. The code is fed into the manufacturer's database via touch-tone telephone, and the computer voice gives back the identification, usually as genus and species. The reliability of this system is very high, and one finds systems like these in heavy use in many food and clinical lab

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> General Principles