Community-acquired pneumonia. The changing picture.

Important changes in the initial management of community-acquired pneumonia have been prompted by the discovery of new respiratory pathogens, the changing susceptibility of traditional pathogens to antimicrobial agents, and the introduction of new antimicrobial agents. Although the clinical presentation may suggest a specific pathogen, findings overlap too much to reliably distinguish the specific cause of the pneumonia on a clinical basis. Useful laboratory studies include Gram's stain and culture of sputum, blood culture, serologic studies, and new tests such as the urinary antigen test for Legionella pneumophila. Empirical antimicrobial treatment must take into consideration that 20% to 30% of cases of community-acquired pneumonia are due to atypical pathogens that are not susceptible to beta-lactam agents.