Clinical microbiology culture media

Culture media in microbiology labs can be divided into four categories:

1. Nutritive media support the growth of most bacteria without giving any particular species an advantage.
2. Enrichment media provide specific nutrients that selectively support the growth of particular bacteria over others.
3. Differential media contain factors that allow colonies of one type of bacteria to be distinguished from another growing on the same agar plate based on their appearance.
4. Selective media contain inhibitory agents, such as antimicrobial drugs, bile salts, and acids, that allow only the selected bacteria to grow.

One medium can fall into several categories. For example, blood agar is a nutritive medium that is differential for hemolysis and MacConkey agar is selective for gram-negative bacteria and differential for lactose fermentation.

Because differential and selective media can be used to distinguish bacteria they are particularly useful in diagnostic microbacteriology.