The term 'immunocompromised' refers to individuals whose resistance to infection has been reduced by disease (congenital or acquired) or by therapeutic measures such as the treatment of malignant disease or organ transplantation. Increased susceptibility to infection may result from a defect in the immune system and/or neutropenia.
The infection may be endogenous, Le arising from within the patient, or exogenous. Endogenous infection may be due to invasion of tissues or organs by bacteria, e.g. E coli, by fungi such as Candida albicans which are present in health in the patient's gastrointestinal tract, or by reactivation of organisms which have remained dormant since primary infection earlier in life. Examples of latent organisms which can cause infection in immunocompromised patients include the herpesviruses (varicella zoster. Herpes simplex. Epstein-Barr virus and cytomegalovirus), mycobacteria. Toxoplasma gondii and leishmania.
Infection is a common cause of death in immunocompromised patients, in whom it may have a fulminating onset or be refractory to therapy. Diagnosis can be difficult as the infections may present atypically, sometimes with very few signs and symptoms until well advanced. Due to
| Microorganisms causing infections in immunocompromised patients | ||
|---|---|---|
| Defect in host response | Microorganism | Infections (examples) |
| Phagocytic abnormalities (Polymorphs, macrophages) |
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| Cell-mediated defects (T cells) |
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| Humoral defects (immunoglobulins) |
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the body's reduced defences against infection, treatment should be started on clinical suspicion, modified according to the results of investigations.
Table lists the important organisms causing infections in immunocompromised patients.