ABSTRACT
The use of culture as a diagnostic technique is described in Chapter 10. The purpose of this chapter to discuss only the principles of enrichment culture. This technique has been in use for more than 120 years. 1 , 2 It consists of incubating a sample in a medium that encourages the growth of an organism of interest, while inhibiting the growth of others. In this way, it can assist the technician in isolating pure colonies of microorganisms from mixtures in which the organisms represent only a very small percentage of the overall flora, and in which isolation by streaking may not be practical. In some cases, as in the isolation of salmonella, first growing a sample in an enrichment culture is a necessary first step to increase the relatively small number of organisms usually found in the primary sample. 3 While the use of enrichment broths in food and environmental microbiology has been demonstrated, their use in clinical microbiology has not fully been established. 4 In some cases, the use of enrichment broths has done little more than add unnecessary cost and extra testing. 5
