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

Elliot Weisenberg, M.D.
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Cite this page: Weisenberg E. Legionella. website. Accessed June 16th, 2024.
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

Gram stain

Immunofluorescence staining

Immunofluorescence staining

Cytology images

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Impression smear from lung

Impression smear from lung

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

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Legionella pneumophila

Legionella pneumophila

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