Which of the following is true of opportunistic pathogens?

• A. They cause disease primarily in hosts with compromised immune systems.
• B. They only infect plants and not humans.
• C. They are never part of the normal microbiota.
• D. They are always capable of causing disease in healthy individuals.

Answer: (A)

Verified step by step guidance

1. Understand the definition of opportunistic pathogens: these are microorganisms that normally do not cause disease in a healthy host but can cause infections when the host's immune defenses are weakened or compromised.
2. Analyze each option by comparing it to the definition: check if the statement aligns with the idea that opportunistic pathogens cause disease mainly in immunocompromised hosts.
3. Evaluate the option 'They cause disease primarily in hosts with compromised immune systems' — this matches the definition of opportunistic pathogens.
4. Consider the other options: 'They only infect plants and not humans' is incorrect because opportunistic pathogens can infect humans; 'They are never part of the normal microbiota' is false since many opportunistic pathogens are part of the normal microbiota; 'They are always capable of causing disease in healthy individuals' is incorrect because they usually do not cause disease in healthy hosts.
5. Conclude that the correct statement is the one that says opportunistic pathogens cause disease primarily in hosts with compromised immune systems.