Bacterial Diseases in Humans

Free Response

Explain the reason why the imprudent and excessive use of antibiotics has resulted in a major global problem.


Antibiotics kill bacteria that are sensitive to them; thus, only the resistant ones will survive. These resistant bacteria will reproduce, and therefore, after a while, there will be only resistant bacteria.

Researchers have discovered that washing spinach with water several times does not prevent foodborne diseases due to E. coli. How can you explain this fact?


E. coli colonizes the surface of the leaf, forming a biofilm that is more difficult to remove than free (planktonic) cells. Additionally, bacteria can be taken up in the water that plants are grown in, thereby entering the plant tissues rather than simply residing on the leaf surface.