Infectious substances are defined as those known or reasonably expected to contain pathogens. Which term best describes these disease-causing agents?

• A. Antibiotics
• B. Pathogens
• C. Sterilants
• D. Microorganisms

Answer: (B)

Infectious substances are defined as those known or reasonably expected to contain agents that can cause disease. The term that best fits this description is pathogens, because pathogens are the disease-causing agents themselves—bacteria, viruses, fungi, or parasites that can lead to illness in a host. Microorganisms is a broader category that includes many organisms, some harmless or beneficial, so it’s not specific enough to describe the disease-causing subset. Antibiotics are drugs used to treat infections, not the agents that cause infection. Sterilants are agents that destroy all life forms on surfaces or materials, not the disease-causing agents themselves. So the precise term for these infectious substances is pathogens.