GPR: 2021 - Week 20

From MGH Learn Pathology

Clinical history

48 yo F with PMHx of metastatic lung cancer on immunochemotherapy p/w fever + SOB. Legionella urine antigen testing is negative. BCYE agar from sputum is shown below +/- UV light. Gram stain shows thin GNRs.


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Legionella anisa
  • Blue-white autofluorescence
  • One of the most common environmental isolates of Legionella
  • Generally non-pathogenic in immunocompetent hosts
  • Numerous case reports of LD in immunosuppressed hosts



Legionella pneumophila

  • Most common cause of LD
  • Legionella urine antigen test only detects Legionella pneumophila (serogroup 1)
  • 80-90% of LD is due to pneumophila with 70% due to serogroup 1
  • Weak (yellow) to no autofluorescence



Legionella erythra

  • Non-pathogenetic species
  • Characteristic red autofluorescence



Legionella clemsonensis

  • Green autofluorescence
  • Isolated in 2006 from a pt with LD
Julian Villalba Leif Helland
Plamar et al. 2016. Legionella clemsonensis sp. nov.: a green fluorescing Legionella strain from a patient with pneumonia. Microbiol Immunol.

Fallon et al. 1990. Legionnaires' disease due to Legionella anisa. Journal of Infection.

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This week's Gross Pathology Roundup was presented by Daniel Pearson MD, PhD on 2021-05-17.