In the context of pathogens, what is meant by 'opportunistic'?

The term 'opportunistic' refers to pathogens that typically do not cause disease in individuals with healthy immune systems but can exploit situations where the host's defenses are compromised. This often occurs in individuals who are immunosuppressed due to conditions such as HIV/AIDS, cancer treatments, chronic diseases, or even through certain medical procedures like surgery.

Opportunistic pathogens take advantage of weakened immune responses to establish infections that would otherwise be controlled by a healthy immune system. This distinction is important because it highlights the role of the host's immune status in the likelihood and severity of infection. Understanding this concept is critical in clinical settings, especially for managing patients who are at higher risk due to health conditions or treatments that impair their immune function.

The other choices do not accurately represent the concept of opportunistic pathogens. For instance, some pathogens might only infect those with strong immune systems, may be largely treatable with antibiotics, or could be harmful irrespective of the host's condition, but these do not apply to the category of opportunistic pathogens.