Which statement describes opportunistic bacteria?

Which statement describes opportunistic bacteria?

• A. Always cause disease regardless of conditions
• B. Never colonize host tissue
• C. Colonize host tissue and cause disease when conditions are favorable
• D. Are always beneficial

Answer: (C)

Opportunistic bacteria are microbes that normally reside harmlessly in or on the body but can cause disease if the host’s defenses are weakened or the environment changes. They are capable of colonizing tissues and, when conditions are favorable—such as immunosuppression, injury to barriers, disruption of normal flora by antibiotics, or the presence of invasive devices—they can become pathogenic. That combination of colonization with disease potential under specific conditions is what this description captures best. In healthy individuals they may behave as harmless colonizers or commensals. They’re not always pathogenic, and they’re not inherently beneficial, which is why the other ideas don’t fit as well.

Opportunistic bacteria are microbes that normally reside harmlessly in or on the body but can cause disease if the host’s defenses are weakened or the environment changes. They are capable of colonizing tissues and, when conditions are favorable—such as immunosuppression, injury to barriers, disruption of normal flora by antibiotics, or the presence of invasive devices—they can become pathogenic. That combination of colonization with disease potential under specific conditions is what this description captures best. In healthy individuals they may behave as harmless colonizers or commensals. They’re not always pathogenic, and they’re not inherently beneficial, which is why the other ideas don’t fit as well.