A microorganism that is capable of causing disease in a susceptible host is called what?

A microorganism that is capable of causing disease in a susceptible host is called what?

• A. Pathogen
• B. Antigen
• C. Toxin
• D. Vector

Answer: (A)

A pathogen is a microorganism or other biological agent capable of causing disease in a susceptible host. This means organisms like bacteria, viruses, fungi, and parasites that can invade tissues, disrupt function, or trigger harmful effects, especially when the host’s defenses are lowered or overwhelmed. The idea of a susceptible host is key—without vulnerability, exposure to a pathogen may not lead to disease. An antigen, by contrast, is any substance that the immune system recognizes and responds to; it signals that a pathogen is present but isn’t itself the disease-causing agent. A toxin is a harmful substance produced by some pathogens that can cause disease symptoms, but the general term for the disease-causing organism is still pathogen. A vector is an organism that transmits a pathogen from one host to another (like a mosquito with malaria) and isn’t the disease-causing agent itself.

A pathogen is a microorganism or other biological agent capable of causing disease in a susceptible host. This means organisms like bacteria, viruses, fungi, and parasites that can invade tissues, disrupt function, or trigger harmful effects, especially when the host’s defenses are lowered or overwhelmed. The idea of a susceptible host is key—without vulnerability, exposure to a pathogen may not lead to disease.

An antigen, by contrast, is any substance that the immune system recognizes and responds to; it signals that a pathogen is present but isn’t itself the disease-causing agent. A toxin is a harmful substance produced by some pathogens that can cause disease symptoms, but the general term for the disease-causing organism is still pathogen. A vector is an organism that transmits a pathogen from one host to another (like a mosquito with malaria) and isn’t the disease-causing agent itself.