Legionella pneumophila: Difference between revisions

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MAIN POINTERS
• Flagellated
• Gram negative,
• Main human pathogen in the Genus  Legionella
• Causes legionellosis or legionnaires’ disease
CHARACTERISTICS
• Non-acid-fast
• Non-sporulatiing
• Non-capsulated
• Rod-like bacteria
• Aerobic
• Non-fermentative
• “unable to hydrolyse gelatin”
• Does not have pigments
• Does not autofluoresce 
• “It is oxidase- and catalase-positive and produces beta –lactamase”
CELL MEMBRANE STRUCTURE
• Although it is gram negative, it still stains badly due to certain lipopolysaccharide in its cell membrane
• Minimum of 35 antigens have already been identified using the pacific characteristics of the antigens on these bacteria cells.
PATHOGENESIS
• Are pathogenic toward amoebae and humans.
• In humans it targets the macrophages, white blood cells.
• Was first found to be pathogenic in 1976 when a group of men became infected. It spread to more than 200 individuals and led to 34 casualties.
• Studies have not yet shown that L. pneumophila can be passed from one person to another. 
• While entering amoeba gives  L. pneumophila protection from environmental stresses.
o For example it protects them from chemicals such as chlorine.
• They enter the cell through phagocytosis
• Inside the cells, they remain in a membrane.
• They use type IV secretion system to introduce certain effector proteins into the host cell which prevents L. pneumophila from combining with endosomes.
• Since membrane does not combine with the lysosomes, which prevents it from being degraded.
• Under the membranes protection it begins to multiply.
GENOMIC
• Major breakthrough for L. pneumophila came in 2004 with the help of genomic sequencing of L. pneumophila.
• DNA studies of 180 strains from Legionella genus show signs of frequent horizontal gene transfer.
• Studies of L. pneumophila’s host Acanthamoeba castellanii provided more information on L. pneumophila’s history.
• L. pneumophila has biphasic life cycle.
TREATMENT
• Macrolides (azithromycin) or fluoroquinolones (moxifloxacin) are two drugs that are commonly used for treating L. pneumophila in people.
Images…
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