What is a characteristic of an opportunistic pathogen?

• A. Infection occurs in healthy individuals only
• B. Infection occurs when the host's immune system is compromised
• C. They are generally less virulent
• D. They are only found in specific geographic locations

Answer: (B)

An opportunistic pathogen is primarily characterized by its ability to cause infections when the host's immune system is compromised or weakened in some way. This means that these pathogens typically reside harmlessly within or on the body but can take advantage of specific conditions, such as immunosuppression, chronic illness, or disruptions in normal flora, to cause disease. Common examples of opportunistic pathogens include certain strains of fungi and bacteria that do not usually cause disease in a healthy host but can lead to serious infections in immunocompromised individuals, such as those undergoing chemotherapy or living with HIV/AIDS.

The other characteristics do not accurately describe opportunistic pathogens. For instance, the idea that infection occurs only in healthy individuals excludes the fundamental nature of opportunistic infections. While some pathogens can be less virulent, this is not a definitive characteristic of all opportunistic pathogens, as some can still be quite harmful in vulnerable hosts. Lastly, the notion that these pathogens are only found in specific geographic locations is misleading; while some may have geographic prevalence, opportunistic pathogens are frequently part of the normal flora of many individuals regardless of location.