<P> The analytical profile index or API is a classification of bacteria based on experiments, allowing fast identification . This system is developed for quick identification of clinically relevant bacteria . Because of this, only known bacteria can be identified . </P> <P> It was invented in the 1970s in the United States by Pierre Janin of Analytab Products, Inc . Presently, the API test system is manufactured by bioMérieux . The API range introduced a standardized, miniaturized version of existing techniques, which up until then were complicated to perform and difficult to read . </P> <P> The API 20E / NE fast identification system combines some conventional tests and allows the identification of a limited number of Gram - negative Enterobacteriaceae or non-Enterobacteriaceae . The test systems are stored in 20 small reaction tubes, which include the substrates . An identification is only possible with microbiological culture . To guarantee a comparability of different samples, follow the instructions of the manufacturer . </P> <P> Before starting a test, one must confirm the culture is of an Enterobacteriaceae . To test this, a quick oxidase test for cytochrome c oxidase is performed . Enterobacteriaceae are typically oxidase negative, meaning they either do not use oxygen as an electron acceptor in the electron transport chain, or they use a different cytochrome enzyme for transferring electrons to oxygen . If the culture is determined to be oxidase positive, alternative tests must be carried out to correctly identify the bacterial species . </P>

How many biochemical tests does the api 20e system contain