Opportunistic Infections

Abstract

In contrast with normal hosts, in which many infectious diseases are usually self-limited, in immunocompromised patients such infections have the potential of becoming serious illnesses characterized by high morbidity and mortality rates. There are also the opportunistic infections that occur almost exclusively in immunocompromised hosts such as patients with HIV disease. Usually widely distributed in the environment, opportunistic pathogens rarely cause serious illness in immunocompetent hosts (1,2). In this context, it is important to note that prompt and correct diagnosis of disseminated opportunistic infections may become crucial as a result of overt differences in the susceptibility to anti-infectious drugs of sometimes closely related opportunistic pathogens. For example, although both Pseudallescheria boydii and Scedosporium prolificans have been recognized as causes of opportunistic hyalohyphomycoses in immunocompromised patients, diagnosis of disseminated disease caused by S. prolificans has been difficult to attain because its signs and symptoms strongly resemble those of pseudallescheriasis and pulmonary aspergillosis. However, early positive identification of S. prolificans may prove to be essential because of its extreme drug tolerance and the related poor prognosis of disseminated disease caused by this fungal pathogen (2).