Biological agents are too small to see with the eye but may be found in infected tissue, body fluids, blood, faeces and urine. In the environment, biological agents can also be found in stagnant water and dirt.
This bacteria, once growing in this petri dish experiment, will not cause infection now because the object is dry, sterile and sealed.
This mortuary trolley was likely exposed to biological agents causing diseases such as cholera and tuberculosis. This object has been in a museum collection for more many decades and it is extremely unlikely any original biological agents remain today.
An example of a contemporary acquisition that does contain harmful biological agents is this piece of ‘fatberg’ extracted from London’s sewer system in 2017.