LEGIONELLA

45 plus species including:

SPECIES

Legionella bozemanii
Legionella dumoffii
Legionella gormanii
Legionella jordanis
Legionella longbeachae
Legionella micdadei
Legionella pneumophila

MICROSCOPIC APPEARANCE

Gram Stain: Negative.
Morphology: Rods and filaments.
Size: 0.3-0.9 micrometers by 2.0-3.0 micrometers.
Motility: Motile by single unsheathed polar flagella in media containing 0.2-1.0ml NaCl. In any other media with a lower or higher concentration of NaCl the cells are unflagellated.
Capsules: None.
Spores: None.
Other: Branched chained fatty acids are often found within the cell walls.

MACROSCOPIC APPEARANCE

Pinpoint colonies appear on Buffered Charcoal Yeast Extract (BCYE) Agar in about 3 days after primary culture; the colony diameter reaches 3-4mm after 5-7 days of incubation at 36 +/- 1.0 degrees C. Colonies are gray, glistening, convex, and circular with an entire edge.

Several species exhibit a blue-white autoflourescence, and most species produce a diffusible, brown pigment on tyrosine-containing agar or F-G Agar. (2)

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Legionella spp. are nutritionally fastidious, aerobic, and have a non-fermentative metabolism.

L-Cysteine and iron salts required in complex media for growth. They are Chemoorganotrophic, and use amino acids as carbon and energy sources. Carbohydrates are neither fermented or oxidized.

HABITAT

Legionella spp. are often isolated in surface waters, mud, lakes and streams, and, warm water systems including thermally polluted streams. They are also airborne.

PATHOGENICITY

Highly pathogenic in humans, notably resulting in pneumonia and Legionnaires' Disease. The term legionellosis is used often to indicate all infections caused by Legionellae. Strains of all species have been directly and indirectly implicated in human pneumonia. Pneumonia caused by L. pneumoniae is commonly referred to as Legionnaires' disease and pneumonia due to L. micdadei is commonly referred to as Pittsburgh pneumonia. At least one Legionella species, L. pneumophila , can also cause a mild, non-pneumonic, febrile disease called Pontiac fever. (2)

RECOMMENDED MEDIA

For culture: BCYE Agar, CYE Agar.
For selective isolation: BCYE Selective Agar.
For maintenance: BCYE Slants.

INCUBATION

Temperature: 35 degrees C. under 5% CO 2 in humid conditions.
Time: Daily for 5 days, then at 7 days and 14 days.
Atmosphere: Aerobic.

REFERENCES

1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society for Microbiology, Washington, D.C.

5. Internet: www.hardlink.com /Bacterial Database Search, February, 1998.

6. Hensyl, B.R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

7. Koneman, et al. 1997. Color Atlas and Textbook of Diagnostic Microbiology , 5th ed. Lippincott, Philadelphia, PA.


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