Lung - nontumor
Legionella pneumophila / Legionnaires disease

Topic Completed: 1 September 2011

Revised: 29 January 2019, last major update September 2011

Copyright: (c) 2003-2018,, Inc.

PubMed search: Legionella pneumophila [title] OR Legionnaires disease [title] pulmonary

Elliot Weisenberg, M.D.
Page views in 2018: 992
Page views in 2019 to date: 790
Cite this page: Weisenberg E. Legionella pneumophila / Legionnaires disease. website. Accessed October 15th, 2019.
Clinical features
  • Initial public attention after epidemic in Philadelphia, Pennsylvania (US) convention of American Legion
  • Caused by Legionella species, a short, Gram negative bacillus (Wikipedia)
  • Retrospective review disclosed sporadic cases since early 1900s
  • Pontiac fever is caused by same bacteria, but without pneumonia, and often subclinical
  • Hilar lymph nodes infected in 50% of cases at autopsy; 25% have spread to other organs
  • Causes: contaminated water in water cooling tanks, drinking water conduits, air conditioning systems and other contained indoor water storage systems
  • Immunosuppressed patients, especially organ transplant recipients, are especially vulnerable to severe disease
  • Interaction with macrophages and dendritic cell subtypes appears to be important for resolution (Front Microbiol 2011;2:126)
  • Erythromycin or other antibiotics, but high mortality in immunocompromised
Microscopic (histologic) description
  • Extensive bronchopneumonia to lobar pneumonia with intra-alveolar neutrophils, macrophages, fibrin; often with leukocytoclastic neutrophilic infiltrate, small vessel vasculitis and necrosis
Microscopic (histologic) images

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Gram stain

Immunofluorescence staining

Cytology images

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Impression smear from lung

Positive stains
  • Dieterle silver stain, monoclonal fluorescent reagent
Electron microscopy images

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Legionella pneumophila

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