Family Legionellaceae

• What type of bacteria is Legionella?

  Gram -ve
• Which enzymes is Legionella positive for?

  Catalase +ve and Oxidase +ve
• What feature allows Legionella to move?

  Flagella
• What type of bacteria is Legionella in terms of its capsule?

  Microcapsule
• How is Legionella primarily transmitted?

  Water aerosols
• What type of environments serve as reservoirs for Legionella?

  Natural aquatic habitats
• What is a key virulence factor of Legionella?

  Lipopolysaccharide
• What does the lipopolysaccharide in Legionella trigger?

  Macrophage activation
• What are the two forms of Legionella?

  Bacillar & filamentous forms
• What are the clinical manifestations of Legionella infection?

  Atypical pneumonia, Pontiac fever
• What is a common characteristic of Legionnaire’s disease?

  Commonly occurs in smokers
• What is a notable laboratory finding in Legionnaire’s disease?

  Hyponatremia
• What is a common symptom of Legionnaire’s disease?

  High fever
• What does a chest X-ray show in Legionnaire’s disease?

  Patchy infiltrate with consolidation
• What specimens are used for microbiological diagnosis of Legionella?

  Sputum, bronchoalveolar lavage
• What staining method is used in microscopy for Legionella?

  Dieterle’s silver staining
• What culture method is used for Legionella diagnosis?

  Buffered charcoal yeast extract agar
• What is the purpose of serological tests in Legionella diagnosis?

  Detect antigens/antibodies
• What is the function of the enzyme-linked immunosorbent assay (ELISA)?

  Produces a detectable signal
• What is a common treatment for Legionella infections?

  Macrolides like Azithromycin
• Which fluoroquinolone is used to treat Legionella?

  Levofloxacin
• What is the role of cysteine and iron in Legionella culture?

  They are required for growth
• What are the virulence factors of Legionella?

  • Lipopolysaccharide (endotoxin)
  • Flagella and pili (movement)
  • Exotoxins
• What are the clinical manifestations of Legionnaire’s disease?

  • Atypical pneumonia
  • Pontiac fever
  • Symptoms:
  • Hyponatremia
  • Diarrhea
  • High fever
  • Chest X-ray: Patchy infiltrate
• What are the steps in the ELISA process?

  1. Antigens/antibodies attached to a surface
  2. Specific antibody/antigen applied
  3. Linked to an enzyme
  4. Substrate added for reaction
  5. Detectable signal produced (color change)
• Is Legionella pneumophila oxidase positive or negative?

  Oxidase positive
• What is the main function of Legionella’s Type IV secretion system?

  To inject effector proteins into host macrophages, manipulating host cell processes and preventing phagosome-lysosome fusion.
• How does biofilm formation contribute to Legionella’s survival?

  Biofilms protect Legionella in aquatic environments and make it resistant to disinfectants.
• What role do siderophores play in Legionella infection?

  They scavenge iron from the environment, which is essential for bacterial growth.