Pneumonia due to Staphylococcus aureus in a patient with AIDS: review of incidence and report of an atypical roentgenographic presentation.

Multiple defects in host defense mechanisms produce an increased incidence of community-acquired bacterial pneumonia in individuals infected with the human immunodeficiency virus. Clinical studies suggest that Staphylococcus aureus is an uncommon cause of such infections, though its incidence is increased in the setting of intravenous drug use, indwelling vascular catheter, and coexistent pulmonary Kaposi's sarcoma or pneumonia due to Pneumocystis carinii. The significantly higher incidence of S aureus pneumonia documented in autopsy series suggests that the infection frequently remains undiagnosed ante mortem. The clinical and radiologic presentation of staphylococcal pneumonia in HIV-seropositive patients is similar to that seen in immunocompetent hosts. However, atypical radiographic patterns can occur. We describe a case of S aureus pneumonia manifested as an infiltrate with focal predominance and multiple cavitary lesions. Such a radiologic appearance has not previously been described in this population. Given the likelihood that pneumonia due to S aureus is significantly underdiagnosed ante mortem, a high index of clinical suspicion is warranted.