The specific microbe that causes disease is called a(n) antigen.
commensal.
infection.
pathogen.
The correct answer and explanation is:
Correct Answer: Pathogen
A pathogen is the specific microbe that causes disease. It is a biological agent—such as a bacterium, virus, fungus, or parasite—that can invade the body and lead to illness. Pathogens are distinct from other types of microbes because they possess the ability to overcome the body’s natural defenses and disrupt normal physiological functions.
Microorganisms are everywhere, but not all of them are harmful. In fact, many microbes are commensals, meaning they live in or on our bodies without causing harm, and often even provide benefits. For example, the bacteria in our gut help us digest food and synthesize vitamins. However, when a microbe crosses the line from being harmless or helpful to causing harm, it is considered a pathogen.
The term antigen refers to a molecule or molecular structure—often found on the surface of pathogens—that is recognized by the immune system as foreign. Antigens trigger an immune response, such as the production of antibodies, but they are not the disease-causing agents themselves.
Infection describes the process by which a pathogen enters, grows, and multiplies within the host organism. An infection may or may not cause symptoms. Not all infections lead to disease; it depends on the virulence of the pathogen and the strength of the host’s immune system.
Understanding the difference between these terms is crucial in microbiology and medicine. Identifying the pathogen responsible for an illness allows healthcare providers to select the appropriate treatment—such as antibiotics for bacteria or antivirals for viruses—and implement public health measures to prevent the spread of the disease.
In summary, while antigens, commensals, and infections are important concepts in disease and immunity, the pathogen is the specific microbe that causes disease.