Laboratory diagnosis of atypical pneumonia.

"Atypical pneumonia" is a term loosely applied to lower respiratory tract infections that are not characterized by signs and symptoms of lobar consolidation. This description can apply to disease caused by a variety of bacterial, viral and even protozoan organisms. In reality, differentiation as to etiology of pneumonia cannot be distinguished on the basis of clinical presentation. This review will discuss the epidemiology, clinical manifestations, and laboratory diagnosis of Mycoplasma pneumoniae, Chlamydia sp., Legionella sp., Bordetella pertussis, and Coxiella bumetii, the most common agents associated with atypical pneumonia. Unfortunately, because many of these pathogens are intracellular, culture systems are either not available or the techniques employed are costly, time-consuming or unsafe. Until molecular techniques are standardized and widely available, diagnosis will depend upon serologic confirmation. Given the relative importance of these organisms as causes of community acquired pneumonia, current practice guidelines recommend empiric therapy with a macrolide in patients well enough to be treated as an outpatient. However, diagnostic tests should be performed in any patient requiring hospitalization.