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Chapter: Microbiology and Immunology: Bacteriology: Miscellaneous Bacteria

Legionella pneumophila: Properties of the Bacteria

L. pneumophila is the causative agent of Legionnaire’s disease, aswell as of Pontiac fever.

Legionella pneumophila

L. pneumophila is the causative agent of Legionnaire’s disease, aswell as of Pontiac fever.

Properties of the Bacteria

 Morphology

pneumophila shows following features:

·           L. pneumophila is a small, slender, pleomorphic, Gram-negative bacillus.

·           L. pneumophila organisms in clinical specimens stain poorlywith Gram staining. They can by stained better by silver impregnation method using Dieterle silver stain.

·           It measures 0.3–0.9 3 2–5 mm with pointed ends and tendency to form filaments in culture on solid media.

·           It is motile by means of one or more polar or subpolar flagella.

·           It is nonsporing and non–acid fast.

 Culture

L. pneumophila is a strict aerobe, grows at an optimum temper-ature of 35°C and an optimum pH of 6.9. It is nutritionally fastidious and grows on the medium supplemented with iron salts and L-cysteine.

Buffered charcoal yeast extract (BCYE) agar: The agarcontaining buffered charcoal, yeast extract, and cysteine is a useful medium for growth of L. pneumophila. It is a slow-growing bacterium and may take 3–5 days to produce visible colonies. The colonies on BCYE agar are circular, gray, or gray-blue and low convex with a slightly irregular margin. Under the microscope, the colonies typically have a ground glass appearance.

 Biochemical reactions

L. pneumophila shows following biochemical properties:

·           It is mostly nonfermenter and derives its energy from the metabolism of amino acids.

·           It does not ferment any sugars and is urease and nitrate test negative.

·           It is catalase positive, oxidase variable, and liquefies gelatin.

·           It hydrolyzes starch and hippurate.

 Other properties

Susceptibility to physical and chemical agents: L. pneumoph-ila is readily killed by 70% ethyl alcohol, 2% glutaraldehyde,and 1% formaldehyde. It is also killed by residual chlorine (5 ppm of chlorine) in chlorinated water in 1 minute, by 1.25 ppm of chlorine in 15 minutes, and by 0.65 ppm of chlorine in 1 hour.

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Microbiology and Immunology: Bacteriology: Miscellaneous Bacteria : Legionella pneumophila: Properties of the Bacteria |


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