Legionella pneumophila

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Legionella pneumophila
TEM image of L. pneumophila TEM image of L. pneumophila
Scientific classification
Kingdom: Bacteria Phylum: Proteobacteria Class: Gamma Proteobacteria Order: Legionellales Family: Legionellaceae Genus: Legionella Species: L. pneumophila
Binomial name
Legionella pneumophila Brenner DJ, Steigerwalt AG, McDade JE 1979

This page is about microbiologic aspects of the organism(s).  For clinical aspects of the disease, see Legionellosis.

For information on other species in Legionella, see Legionella.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C). L. pneumophila is a pleomorphic, aerobic, catalase-positive, oxidase-positive, non-spore-forming, non-capsulated, motile, Gram-negative bacteria. Although Legionella is categorized as a Gram-negative bacterium, it stains poorly to Gram stain due to its unique lipopolysaccharide-content in the outer psuedospamodulating leaflet of the outer cell membrane.

Microbiological Classification

• Bacteria; Proteobacteria; Gammaproteobacteria; Legionellales; Legionellaceae

Microbiological Characteristics

• L.pneumophila is a ubiquitous aquatic organism that thrives in warm environments (32°- 45°C).
• L. pneumophila is a pleomorphic, aerobic, catalase-positive, oxidase-positive, non-spore-forming, non-capsulated, motile, Gram-negative bacteria.
• Although Legionella is categorized as a Gram-negative bacterium, it stains poorly to Gram stain due to its unique lipopolysaccharide-content in the outer psuedospamodulating leaflet of the outer cell membrane.
• Legionella is non-fermentative and is unable to hydrolyse gelatin or produce urease.
• At least 46 species and 70 serogroups of Legionella have been identified.

Legionella grow on buffered charcoal yeast enriched with L-cysteine

• The natural habitat of Legionella is freshwater, where they often live within protozoa such as Vermamoeba vermiformis, Acanthamoeba spp., Tetrahymena pyriformis, and Naegleria spp . It utilizes a similar method to enter and infect phagocytes.

Life Cycle

• There are two major phases to the life cycle.

• The first is called the replicative phase. During this period, the bacteria are nonmotile and have a low toxicity.
• In the second phase, called the infectious phase, the bacteria are shorter and thicker.

Gallery

Colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria under 8000x magnification.^{Courtesy of Janice Haney Carr, Public Health Image Library}

Colorized scanning electron micrograph (SEM) depicted a large grouping of Gram-negative Legionella pneumophila bacteria under 10,000x magnification.^{Courtesy of Janice Haney Carr, Public Health Image Library}

Legionella micdadei bacteria using TATLOCK conjugate in egg yolk sac suspension, DFA-stained photomicrograph with positive HEBA stain.^{Courtesy of Ann Herbert, Public Health Image Library}