- 1. Denoting an organism capable of causing disease only in a host whose resistance is lowered, e.g., by other diseases or by drugs. 2. Denoting a disease caused by such an organism.
* * *1) of, relating to, or being a microorganism that is usu. harmless but can become pathogenic when the host's resistance to disease is impaired2) of, relating to, or being an infection or disease caused by an opportunistic organism <Pneumocystis carinii pneumonia and other \opportunistic infections that kill AIDS patients (N.Y. Times)>
* * *adj.denoting a disease that occurs when the patient's immune system is impaired by, for example, an infection, another disease, or drugs. The infecting organism, which is also described as opportunistic, rarely causes the disease in healthy persons. Opportunistic infections, such as Pneumocystis carinii pneumonia and that caused by the MAI complex (see Mycobacterium), are common in patients with AIDS.
* * *op·por·tu·nis·tic (op″ər-too-nisґtik) 1. denoting a microorganism that does not ordinarily cause disease but that becomes pathogenic under certain circumstances, such as in immunodeficiency conditions. 2. denoting a disease or infection caused by such an organism.
Medical dictionary. 2011.