obligate intracellular bacteria

Question 1

Which evidence supports a role of C. trachomatis as a cause of ovarian
cancer?

Answer 1

1. infection persists for long time without causing symptoms. (stay at infection site long enough to induce long term damage that can lead to cancer)
2. Induces DNA damage
3. Manipulate oncogenic signaling (p53, myc, RAS etc)

Question 2

cell-autonomous defense functions to prevent infection with intracellular bacteria. Name three different strategies and explain why they are particularly efficient against intracellular bacteria.

Answer 2

1. upregulation of p53- it incuces cell cycle arrest and apoptosis which leads to destruction of cell infected by bacteria and also the bacteria propagation is inhibited.
2. proteosomal degradation and ubiquitination- causes the destrurction of intracellular bacteria using proteosomes.
3. Cellular innate immune defence- Can phagocytose and destroy pathogens.

Question 3

obligate intracellular bacteria escape the host immune defense. Name four general mechanisms which are related to their obligate intracellular
lifestyle.

Answer 3

1. deubiquitination of inclusion by cdu1
2. Chlamidial protease likeactivity factor (CPAF) -paralysis of neutrophils
3. downregulation of tumor supression factor p53

Question 4

Explain the typical courses of Coxiella burnetti infections. In which cellular compartment does the pathogen replicate?

Answer 4

Q fever- acute flu-like symptoms
prolonged high fever
headache and malaise.

they replicate in macrophages, freeliving amoeba and in the gut epithelium of ticks

Question 5

Which bacteria cause Rocky Mountain Spotted fever? Explain shortly the life cycle of the bacteria and how humans are infected.

Answer 5

Rickettsia rickettsii

life cycle: The most common vector of Rickettsia reckettsii is tick (hard bodied ticks).

1. ticks gets infected by the bacteria when they feed on the blood of infected rodents during the larval or nymph stages.
2. once a tick is infected, its infected or life. Male ticks can infect female ticks through mating and femal ticks can infect their offsprings through transovarian transmission.
3. mammals including humans can be infected in different ways.
   a. bite from infected tick.
   b. eating food contaminated with infected mammals feaces.
   c. infected persons faeces gets into contact with open wound of an uninfected person.

Question 6

Which bacteria cause epidemic typhus? Explain the route of infection and the mechanism underlying the spreading of these bacteria in the tissue.

Answer 6

Rickettsia prowazekii

Enter skin through skin or mucosa and invade endotheilial cells.
with the help of phospholipase and hemolysin, they escape phagosomes
they spread from cell to cell by rapturing cells
Cells damage causes disruption of tight junctions vascular permeability.

Question 7

Which of the features of Coxiella justify the classification as bioweapon category B?

Answer 7

a. aerosol transmission
b. low infectious dose
c. debilitating nature of Q- fever

Question 8

in which cell type replicates Anaplasma phagocytophilum? Which features of these host cells are relevant for obligate intracellular bacteria?

Answer 8

Replicates in mammalian white blood calls and in tick midgut cells and salivary glands.

a. they use host cholesterol to stablize cell membrane. they dont synthesise LPS and peptidoglycan wall.
b. Anaplasmauses the autophagicpathway to generate niche for replication in Granulocytes
c. Anaplasmainterferes with apoptosis signaling

Question 9

How does Anaplasma modify its host cell to efficiently replicate?

Answer 9

interfere with immune signaling and apoptosis

Question 10

In which cell type replicates Ehrlichia chaffeensis?
Do you know other pathogenic bacteria, which replicate in the same cell type?
How do these bacteria modify these host cells, to be able to efficiently replicate?

Answer 10

monocytes and macrophages

Coxiella burnetti

a. they use host cholesterol to stablize cell membrane. they dont synthesise LPS and peptidoglycan wall.
c. interferes with apoptosis signaling