Legionella
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Legionella is a Gram negative bacterium, including many species that cause legionellosis or Legionaires' disease, most notably L. pneumophilia. At least 46 species and 70 serogroups have been identified. On the side-chains of the cell wall are carried the bases for the somatic antigen specifity of these organisms. The chemical composition of these side chains both with respect to components as well as arrangement of the different sugars determines the nature of the somatic or O antigen determinants, which are such important means of serologically classifying many Gram-negative.
At least 14 different serovars of L. pneumophila have been described as well as several other species being subdivided into a number of serovars. Sera have been used both for slide agglutination studies as well as for direct detection of bacteria in tissues using fluorescent-labelled antibody. Specific antibody in patients can be determined by the indirect fluorescent antibody test. ELISA and microagglutination tests have also been successfully applied.
Legionella pneumophila is non-acid, fast non-capsulated rods, aerobic and do not hydrolyse gelatin or produce urease. They are non-fermentative. L. pneumophila is neither pigmented nor does it autofluoresce. It is oxidase and catalase positive, produces beta-lactamase.
L. pneumophila is an intracellar pathogen. The internalisation of the bacteria is enhanced by the presence of antibody and complement. A pseudopod coils around the bacterium in this unique form of phagocytosis. Once internalised, the bacteria surround themselves by a membrane-bound phagolysosome. This becomes a vescicle, within which the bacteria multiply. They produce a 39kDa metalloprotease into culture fluids, which is cytotoxic for some cultured tissue culture cells.nn:Legionella-bakterie no:Legionella