Opportunistic Infections

the body's defences against invasion by potential pathogens or as a side-effect of drugs and other therapeutic measures. Their particular frequency as iatrogenous diseases has made them a danger common enough and grave enough to necessitate constant watch for their development when any patient is under treatment with corticosteroids, cytotoxic agents and broad-spectrum antibiotics, or with radiotherapy. 'Opportunistic infections' are often the immediate cause of death in cases of chronic debilitating disease, particularly cancer. In assessing their importance in cases of this sort it has to be remembered that they have to some extent taken the place of terminal bronchopneumonia as the closing stage in the course of the illness. Many patients with cancer nowadays live much longer than would have been the case before the introduction of modern advances in the treatment of neoplastic diseases; moreover, simple pneumonia in these patients is often not the danger that it was once, for it may be cut short and cured by giving antibiotics. Many of the micro-organisms that cause 'opportunistic infections' are resistant to drugs, or respond only to treatment with drugs, such as the antifungal antibiotic, amphotericin B, of which the side-effects are liable to be particularly dangerous in these chronically debilitated patients. It is sometimes the case, then, that there is nothing to be done to overcome an 'opportunistic infection'. As has been mentioned, this cannot be an excuse for failure to establish early diagnosis of the presence of such infections their prevention, or their successful treatment, may provide the chance of bringing the patient's underlying disease under control and, at least in some cases, of restoring his health. The four cases summarized in this paper include instances of infection by bacterial, fungal, viral and protozoal 'opportunists'. In one of the cases all four of these groups of organisms were represented, and no fewer than seven different types of organism were recognized at necropsy.