Common in many environments, including soil and aquatic systems, with at least 50 species identified.
Requires the presence of cysteine and iron to grow and therefore does not grow on common blood agar media used for laboratory based total viable counts or on site dipslides.
Many hospitals use the Legionella Urinary Antigen test for initial detection when Legionella pneumonia is suspected (results can be obtained in a matter of hours rather than the five days required for culture).
L. pneumophila, causes Legionnaires Disease. L.longbeachae causes Pontiac Fever.
Thin, aerobic, pleomorphic, flagellated, non-spore forming, Gram-negative bacterium of the genus Legionella.
L. pneumophila is the primary human pathogenic bacterium in this group and is the causative agent of legionellosis or Legionnaires’ disease.
L. pneumophila is a gram-negative, non-encapsulated, aerobic bacillus with a single, polar flagellum often characterized as being a coccobacillus. It is aerobic and unable to hydrolyse gelatin or produce urease. It is also non-fermentative.
It is oxidase- and catalase-positive, and produces beta-lactamase.
L. pneumophila has a colony morphology that is gray-white with a textured, cut-glass appearance; it also requires cysteine and iron to thrive.
Legionella stains poorly with gram stain (due to its unique lipopolysaccharide-content), stains positive with silver, and is cultured on charcoal yeast extract with iron and cysteine.
Therapy:
Important considerations: The choice of an agent should be based on local antimicrobial sensitivities, site of infection, cost, and comorbid conditions. Generally, the most common agents/regimens are listed first. Total duriation of therapy is usually 7 to 10 days, however, for more severe cases or for immunosuppressed patients consider prolonging therapy for up to 3 weeks.
