Legionella and the clinical microbiologist.

Legionella species are important etiologic agents of sporadic and epidemic community-acquired and nosocomial respiratory disease. The list of species continues to expand, and tools for classification and characterization of isolates have become increasingly sophisticated. These organisms are associated with aquatic habitats and are transmitted by aerosol or direct contact. Bacterial culture is the cornerstone of laboratory diagnosis. Careful surveillance of infections is important, because infections potentially can be prevented.