Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

What term refers to media that permits the growth of one type of organism but inhibits the growth of others?

1. Selective media

2. Enriched media

3. Naturally media

4. Differential media

The correct answer is: Selective media

Selective media is designed specifically to allow the growth of one type of organism while inhibiting the growth of others. This type of media contains inhibitors that limit the growth of unwanted microorganisms, making it easier to isolate the target organism for further study or identification. In the context of microbiology, selective media is invaluable for differentiating between microorganisms that may be present in a mixed sample. For instance, if a laboratory is trying to isolate a particular type of bacteria from a sample that contains various species, selective media can provide the necessary environment to promote only the desired bacteria while suppressing the growth of others. Enriched media, on the other hand, provides additional nutrients to boost the growth of fastidious organisms but is not specifically designed to inhibit others. Naturally occurring media typically refers to substrates found in the environment and does not imply selectivity or inhibition. Differential media allows for the differentiation between various types of organisms based on specific biochemical reactions but does not necessarily inhibit the growth of others—it often supports the growth of multiple organisms while allowing for differentiation based on their characteristics. Overall, the key characteristic of selective media is its ability to effectively suppress the growth of non-target organisms, making it essential for the isolation and identification of specific microbes in various laboratories.