Week 2: Legionella, Bordetella, Mycoplasma And Chlamydia

Front 1

Under the microscope you see a gram-negative rod. You acquired these bacteria from a charcoal, iron, and cysteine supplemented plate. What are you looking at?

Back 1

Legionella pneumophila

Front 2

Your friend, who is in the hospital, was recently diagnosed with having legionnaire's disease. Should you be worried about getting sick directly from him / her?

Back 2

No. Legionella pneumonia is not transmitted person to person.

Front 3

How is L. pneumophila spread?

Back 3

by water aerosols

Front 4

Define: Structured communities of bacterial cells enclosed in a self-produced polymeric matrix and adherent to an inert or living surface.

Back 4

Biofilms

Front 5

Within a biofilm, can only one cell type be found of the bacteria?

Back 5

No, there are multiple cell types within a biofilm

Front 6

How did bacteria evolve the ability to develop biofilms?

Back 6

- Developed in the environment
- based on competition with other organisms
- biofilm development is triggered by LOW levels of antibiotics (at levels that don't inhibit bacterial replication)
- signal transduction system senses low levels of antibiotics and induces biofilm formation

Front 7

Within a biofilm, specialized cell types (persisters) are important because...

Back 7

- persisters are a hardy cell type that can survive the onslaught of antibiotics, differentiate to form other cell types, and reform a biofilm

Front 8

Amoebae in the environment can also be considered a selective pressure on bacteria. How have some bacteria responded? Why is this important?

Back 8

- amoeba feed on biofilms and eat the bacteria
- some bacteria have responded to this by evolving the ability to survive within the amoeba (after ingestion)
- because of this, some bacteria can also tolerate being "eaten" by a macrophage

Front 9

What organisms are considered the reservoir for Legionella?

Back 9

amoebae

Front 10

How are L. pneumonia organisms able to get in to the human alveoli?

Back 10

- water contains amoeba that have consumed legionella
- amoeba inspired via water aerosol by human
- legionella replicate in amoeba, lyse out of cell
- are taken up by alveolar macrophages

Front 11

Describe how L. pneumonia switch between replicative and transmissive forms.

Back 11

- legionella swim in the water and will shut off motility when in a vacuole (in the amoeba)
- they will switch to a replicative form
- in the replicative form the bugs acquire nutrients and keep on replicating
- eventually nutrients become limiting in the vacuole and the legionella will revert back to the transmissive form
- the bug will lyse out of the cell (via the use of cytotoxin), back to the external environment
- cycle continues

Front 12

What host factors are known to predispose individuals to infection with legionella?

Back 12

- smoking
- advanced age
- COPD
- immunosuppression (transplant, etc)

Front 13

Does legionella quorum sense?

Back 13

No, uses a simpler mechanism that monitors nutrient level

Front 14

How is differentiation of intracellular (legionella) bacteria induced?

Back 14

- if there are enough nutrients present in the cell then the legionella will continue to replicate
- if there are NOT enough nutrients in the cell, legionella will make ppGpp (an alarmone) that triggers the bacteria in the vacuole to convert to the transmissive form and lyse out of the bacteria

Front 15

How does legionella respond to low levels of amino acids and fatty acids in its host cell?

Back 15

- responds to low levels of amino acids by generating ppGpp through RelA
- responds to low levels of fatty acids (etc.) by generating ppGpp through SpoT
- will lead to expression of components for stress resistance (like motility, spreading, blocking phagosome maturation)

Front 16

How do legionella organisms avoid degradation in host lysosome?

Back 16

- when taken up by macrophage, legionella is surrounded by ER (rather than going to the lysosome) and go through a process kind of like autophagy
- the bacteria are protected and able to replicate
- association with ER is mediated by Type IV secretion system factors

Front 17

How does legionella deliver virulence factors to the macrophage?

Back 17

- via Type IV secretion system

Front 18

What do Type IV secretion systems allow bacteria to do?

Back 18

- allow bacteria to pass plasmid DNA from donor to recipient
- allow DNA uptake or release to environment

Front 19

Why is legionella considered an opportunistic pathogen?

Back 19

- will typically only cause disease in those with high risk (older, smoker)
- healthy people are able to clear it

Front 20

How are macrophages able to prevent legionella from replicating?

Back 20

- macrophages can restrict the iron supply to the bugs via activation by gamma-interferon

Front 21

Under the microscope you see a small gram-negative coccobacillus. The bacteria was originally cultured on Bordet-Gengou medium. It is encapsulated and hemolytic. It is a strict aerobe. What might you be looking at?

Back 21

Bordetella pertussis

Front 22

Where is the natural reservoir for bordatella pertussis?

Back 22

human respiratory tract

Front 23

How does B. pertussis (and other bacteria) respond to changes in the environment?

Back 23

B. pertussis uses a two-component regulatory system (BvgS, BvgA)
- in response to a change in the environment, sensor kinases on the membrane will auto phosphorylate
- the phosphate will be transferred to a response regulator (a DNA binding protein)
- the response regulator can then go and bind to promotors on the DNA and act as an activator or repressor
- virulence factors can then be expressed / controlled

Front 24

What are the (6) virulence factors of B. pertussis?

Back 24

- fimbriae
- pertactin
- filamentous hemagglutinin
- adenylate cyclase
- tracheal cytotoxin
- pertussis toxin

Front 25

How does B. pertussis adhere to ciliated epithelium of the upper respiratory tract?

Back 25

- Filamentous hemagglutinin (Fha) binds to carbs on ciliated cells
- Pertussis toxin also acts as an adhesin
- Pertactin and pili help as well

Front 26

What are the components of the B. pertussis vaccine and why?

Back 26

- the components that help pertussis to adhere to the ciliated epithelium are a part of the acellular vaccine
- the reasoning behind this is that if you can create antibodies that can prevent interactions between the bacteria and the glycolipids on the ciliated respiratory cells then you can prevent colonization

Front 27

How is pertussis, the disease, mediated?

Back 27

through the use of A-B type toxins

- when bacteria binds to host cell it can secrete toxins
- A = active subunit
- B = binding subunit (to host membrane)

Front 28

What does B. pertussis do to host levels of cAMP and how does it do it?

Back 28

B. pertussis secretes 2 toxins that ELEVATE host cAMP
- pertussis toxin: delivered via Type IV secretion
- calmodulin-dependent adenylate cyclase: secreted; only active inside host cells

Front 29

How does bacterial calmodulin-dependent adenylate cyclase assist in survival of the bacteria?

Back 29

it will inhibit phagocytic functions of:
- chemotaxis
- phagocytosis
- superoxide production

Can stimulate apoptosis

Front 30

What is the actual "cause" (toxin) behind whooping cough? How does it work?

Back 30

- Tracheal cytotoxin is the cause of whooping cough
- it is a fragment of peptidoglycan and will intoxicate and lead to extrusion of ciliated epithelial cells in the respiratory tract (fragments are generated due to breakdown / regrowth of cell wall in bacteria)

Front 31

Would you be able to use penicillins and cephalosoporins to treat against mycoplasma?

Back 31

No
- mycoplasma do not have a cell wall and therefore antibiotics that target cell wall synthesis (like penicillins and cephalosporins) will not work

Front 32

Where does mycoplasma pneumoniae typically colonize in the body?

Back 32

- ciliated respiratory epithelium using an attachement organelle

Front 33

How are mycoplasma able to evade the immune system?

Back 33

- variable lipoproteins on surface can change over time (what is expressed on the surface of the cell changes) to change the antigenic profile of the bug
- the mycoplasma can also invert the promoter on its mobile element to lead to efficient changes in gene expression
- all this leads to rapid differentiation

Front 34

What toxin is secreted by mycoplasma and what does it do?

Back 34

- CARDS toxin
- it is an ADP-ribosylating, vacuolating toxin (of the respiratory epithelium)
- an important virulence factor that leads to inflammation and pathology

Front 35

What are the consequences of colonization by mycoplasma pneumoniae?

Back 35

- ciliary activity impaired and necrosis of the epithelium
- inflammatory response induced (via the toxins)
- bacteria are around for a long time

Front 36

What is the reservoir for chlamydia pneumonia and how does it interact with phagocytic cells?

Back 36

- reservoir is the human respiratory tract
- can alter host cell biology and replicated in phagocytic cells (kind of like legionella)
- it is an obligate intracellular pathogen

Front 37

How are legionella and chlamydia similar?

Back 37

- both will replicate inside host cells
- both will convert back to an infectious form when done replicating (EB for chlamydia) and lyse out of the cell

Front 38

What needs to be considered in the treatment of chalmyida pneumonia?

Back 38

- since it is an obligate intracellular bacteria the drug needs to cross 4 membranes
- tetracycline and erythromycin
- the EB (infectious form) is not metabolically active so will not be sensitive to antibiotics that require replication