The role of atypical pathogens in community acquired pneumonia

The atypical pathogens in community-acquired pneumonia traditionally have i ncluded Mycoplasma pneumoniae, Chlamydia pneumoniae, and Legionella spp. Re cent studies documenting their epidemiology and clinical characteristics ha ve shown that these organisms are indistinguishable from the pneumococcus. Furthermore, therapy no longer depends on the specific bacterial cause of c ommunity-acquired pneumonia. Etiologic diagnosis is still difficult, althou gh new methods are becoming available. This article focuses on these issues and on why the term atypical is no longer meaningful.