Chapter 6 - Opportunistic infections

Abstract

This chapter discusses opportunistic infections. Many opportunistic infections are acquired in hospital. Opportunistic infections are a major cause of illness and death in oncology patients and are the leading cause of death in recipients of renal transplants. Severely immunocompromised patients may develop simultaneous infections with several different types of opportunist organisms. Opportunistic infections are the usual cause of death in patients with the acquired immunodeficiency syndrome, AIDS. The term “opportunist― is not an exact one. Opportunist organisms have three main characteristics: (1) they are usually organisms of low pathogenicity, (2) they cause serious infections mainly when the host's defense mechanisms against infection are impaired, and (3) they can behave as conventional pathogens but under opportunistic conditions may cause atypical clinical presentations or disseminated lesions. The opportunistic conditions present in an individual patient greatly influence the type of infections that the patient may develop. These conditions include impaired host defenses, instrumentation and surgery, administration of broad-spectrum antibiotics, structural damage to an organ or system, and foreign bodies.