What term describes pathogens that can be harmful and can lead to disease?

The term that describes pathogens capable of causing harm and leading to disease is "pathogens." Pathogens are biological agents that can cause illness in a host and include various types of organisms such as bacteria, viruses, fungi, and parasites. Their primary characteristic is their ability to disrupt normal biological processes, leading to infection and disease in humans and other living beings.

The other terms mentioned, while related to microorganisms, do not specifically define harmful agents. Nonpathogens refer to those microorganisms that do not cause disease or are beneficial to their hosts. Microorganism is a broader category that includes all microscopic organisms, both pathogenic and nonpathogenic. Bacteria specify a certain type of microorganism; while many bacteria are pathogenic, not all bacteria are harmful. Hence, when referring specifically to agents that can lead to disease, the appropriate term is indeed "pathogens."