Legionella pneumophila

Question 1

What type of pathogen is Legionella pneumophila?

Answer 1

opportunistic

Question 2

Legionnaires Disease

Answer 2

• Caused by Legionella pneumophila
• Invasive infection of lung (alveolar) macrophages

Question 3

Describe the physical features of Legionella pneumophila.

Answer 3

• Gram negative bacillus

Question 4

How does Legionella pneumophila interact with oxygen (areobe, anareobe…)?

Answer 4

Obligate aerobe

Question 5

Is Legionella pneumophila intracellular or extracellular? What does this tell us?

Answer 5

• faculatiative intracellular pathogen (can replicate inside or outside a cell)
• forms biofilms

Question 6

How is L. pneumophila transmitted?

Answer 6

• waterborne disease (can be aerosolized)
• can contaminate water cooling towers and air conditioning units

Question 7

Describe the L. pneumophila enviromental lifecycle.

Answer 7

• found in freshwater enviroments
• repliacte in ameoboes which phagocytose like macrophages and then they cause the ameoboes to self lysis releasing the bacterium

Question 8

What are the models of Legionella celular pathogenesis?

Answer 8

• fcailiates its uptake by mediating phagocytosis by a complement receptor
• subverts host cells processes via effectors (blocks phagolysosome fusion and hijacks host ubiquitin machinary): allows bacterium to live in phagocytes

Question 9

Leigonella containing vacuole

Answer 9

• formed by prevention of endosomal acidification (protected replication niche)
• functions to recruit ER derived vesicles (may deliver nutrients to bacteria or nutrients may be derived from autophagic pathway)

Question 10

T4SS

Answer 10

• conjugation
• Transports proteins and/ or DNA bound to proteins
• extends to host cell and can secrete 350 effectors some of which are aquired from the ameoba

Question 11

Describe the transition from replication to transmission for Leigonelle.

Answer 11

• the replicating bacteria do not express virulence traits
• this is mediated by ppGpp and spoT

Question 12

What does alarmone ppGpp do to legionella?

Answer 12

induces virulence

Question 13

What happens to ppGpp in nutrient rich (NR) enviroments? nutrient poor (NP) enviroments?

Answer 13

• It is degraded by spoT and virulence decreases (NR)
• spoT stops degrading ppGpp (NP)