The etiology of community-acquired pneumonia at an urban public hospital: Influence of human immunodeficiency virus infection and initial severity ofillness

In a prospective study, the etiology of community-acquired pneumonia (CAP) was investigated among consecutive patients admitted to an academic, urban public hospital in Seattle. The study population was uniquely young, was pr edominantly male, and had high rates of homelessness, cigarette smoking, al coholism, injection drug use, and human immunodeficiency virus (HIV) infect ion. Leading causes of CAP among HIV-negative patients were aspiration, fol lowed by Streptococcus pneumoniae, Legionella species, and Mycoplasma pneum oniae. Among HIV-positive patients, Pneumocystis carinii, Mycobacterium tub erculosis, S. pneumoniae, and M. pneumoniae were the most common etiologic agents. Severe CAP was associated with typical bacterial infections and asp iration pneumonia but not Legionella infection among HIV-negative patients and with Pseudomonas aeruginosa infections among HIV-positive patients. The se findings emphasize the need to tailor empirical antibiotic therapy accor ding to local patient populations and individual risk factors and highlight the importance of recognizing underlying HIV infection in patients who are hospitalized with CAP.