Miniaturized detection-identification kits such as API, Enterotube, Vitek, Biolog and B D Crystals are typical examples. All work on basically the same principle: a pure isolate of a bacterium is Gram stained and subjected to a small range of rapid chemical tests, e.g., catalase, oxidase or coagulase. This enables selection of the correct test kit type. A culture is then suspended in saline and added to a succession of wells, which contain a variety of growth substrates with or without indicators: the culture is then incubated. As the organism grows and ferments and utilizes the substrate, the by-products of its metabolism induce a colour change in the reagent. The combination of changes is compared either manually or automatically against a database derived from profiling literally hundreds of different bacteria isolates. This hopefully relatively unique "fingerprint" of reactions allows an identification to be made.
In many cases the system is microprocessor driven and a "fit" to the profile is also given, providing a level of assurance of an accurate identification. Most of these systems provide an identification between four and 24 hours, considerably faster than conventional methods.
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