BSCI 424 — PATHOGENIC MICROBIOLOGY — Fall 2000

Legionella Summary

Legionella pneumophila:

  Retrospective study of outbreak data led to discovery of this organism in the late 1970’s

  Commonly present in water sources; grow and multiply intracellularly in protozoa

  Facultative Gram-negative intracellular pathogen (see WebLinked image) capable of growing inside human white blood cells (leukocytes including neutrophils and pulmonary macrophages)

  Cell-mediated immunity important in protection

  Infection via continueing common-source airborne exposure, e.g., air conditioning cooling towers, evaporative condensers, nebulizers, whirlpools, etc.

  Human pulmonary infections with two clinical presentations:

1. Mild flu-like illness called Pontiac fever
2. Severe form of pneumonia (Legionnaires’ disease)

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