Bacterial infections in HIV: the extent and nature of the problem

Leucopenia and neutropenia in HIV appears to be much less common than in the context of haematological malignancies although severe neutropenia (< 0.75 x 10(9)/l) occurs in as many as 70% of patients with AIDS often related to concomitant drug therapy. In addition to low numbers of neutrophils there is also some evidence of defective neutrophil function in HIV/AIDS (chemotaxis, bacterial killing, phagocytosis and superoxide production). However the frequency and importance of these defects is as yet not known because simple and reproducible tests of neutrophil function are not yet available to the majority of clinicians. Despite the relative scarcity of severe neutropenia in early HIV, bacterial sepsis is a major clinical problem which usually manifests itself as either pneumonia, bacteraemia or both at a frequency of between 8-20 per 100 person years depending upon location, risk activity etc. Amongst drug users, the inhalation of recreational drugs particularly after Pneumocystis carinii pneumonia (PCP) has been shown to be a major risk factor for pneumonia. The incidence of bacterial sepsis in patients with AIDS is more difficult to determine since it is often overshadowed by other more dramatic opportunistic infections. However, throughout the course of AIDS, bacterial infections are a common problem particularly in the presence of one or both of concomitant drug therapy and indwelling intravenous lines utilized in late stage disease. Consequently, since bacterial infections are common and cause considerable morbidity and mortality they should be considered in the differential diagnosis of most presentations.