opportunistic infection [L, opportunus, convenient, icus, form] , 1. an infection caused by normally nonpathogenic organisms in a host whose resistance has been decreased by disorders such as diabetes mellitus, human immunodeficiency virus (HIV) infection, or cancer; a surgical procedure such as a cerebrospinal fluid shunt or a cardiac or urinary tract catheterization; or immunosuppressive drugs. Long-term use of antibiotics or other drugs may also affect the immune system, creating an opportunity for microorganisms not usually pathogenic to become pathogens. People with HIV are particularly susceptible to such infections. 2. an unusual infection with a common pathogen, such as cellulitis, meningitis, or otitis media.
