Empiric therapy for the immunocompromised host

The use of empiric therapy for immunocompromised hosts has been one of the major advances in the management of such patients. Such therapy has been put into practice primarily for patients with neutropenia induced by cytotoxic chemotherapy. The empiric antibiotic regimens include in their coverage the bowel, skin, and intravenous-catheter flora anticipated for patients in a particular hospital. Less often, physicians treat empirically for opportunistic infections that complicate defects in helper cells, although empiric therapy for presumed Pneumocystis carinii pneumonia and Toxoplasma gondii infection of the central nervous system has become commonplace for patients infected with human immunodeficiency virus. Physicians also should consider environmental factors that expose patients to certain opportunistic organisms. Examples of such pathogens include Mycobacterium tuberculosis and Histoplasma capsulatum. The particular microorganisms considered to be opportunistic vary in different parts of the world and in different hospitals, and their designation as such may change rapidly. Multiple environmental exposures and immune defects, rather than just one factor, may be responsible for opportunistic infections and should be investigated and taken into account when empiric therapy is planned. Preventive measures, including simply rigorous hygiene, should precede and may obviate the need for empiric therapy.