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Before further discussion of Category A and Category B, it is important to define two additional terms that are used in the classification process.


An infectious substance containing a pathogen that is intentionally propagated, eg, bacteria grown on bacteriological medium. An example of a culture is shown in the image below.

Patient specimen

Patient specimens are human/animal materials collected directly from humans/animals and transported for research, diagnosis, investigational activities, or disease treatment/prevention. Patient specimens include excreta, secreta, blood and its components, tissue and tissue swabs, body parts, and specimens in transport media (e.g., transwabs, culture media, and blood culture bottles).*

*It is important to note that this means specimens that have been collected into these transport media, but have not yet been incubated and micro-organisms are not actively growing in or on the media. If there is growth in the transport media, it is classified as a culture.