Lecture 5/6

Question 1

Agents that case infectious diseases?

Answer 1

Pathogens

Question 2

What are the 2 types of immune defense systems and when are they used?

Answer 2

Innate immune responses and adaptive immune responses.
Innate is used immediately after an infection begins and doesn’t depend on hosts prior exposure to the pathogen.
Adaptive immune responses operate later in an infection and highly specific for pathogen that induced them.

Question 3

Why is a human host a good environment for the pathogen?

Answer 3

Nutrient rich, warm, moist environment and remains at a uniform temperature and constantly renews itself.

Question 4

What is normal flora?

Answer 4

The normal flora are bacteria which are found in or on our bodies on a semi-permanent basis without causing disease.

Question 5

what are primary pathogens?

Answer 5

can cause overt disease in most healthy people, usually distinct from the normal flora. different from commensal organisms .

Question 6

what are the 5 steps for a pathogen to survive and multiply in a host?

Answer 6

1) Colonize the host
2) find a nutritionally compatible niche in the hosts body
3) avoid, subvert, or circumvent the hosts innate and adaptive immune response
4) replicate, using host resource
5) exit and spread to a new host

Question 7

What is a virulent gene? and virulence factor?

Answer 7

Genes that contribute to the ability of an organisms to cause disease. The proteins they encode are called virulence factors.

Question 8

where are virulence genes frequently clustered together?

Answer 8

either in groups on the bacterial chromosome called pathogenicity islands or on extrachromosomal virulence plasmids.

Question 9

What are adhesins?

Answer 9

Proteins or protein complexes that recognize and bind to host cell surface molecules

Question 10

How do pathogenic bacteria and parasites infect epithelial surfaces?

Answer 10

There are specific mechanisms for overcoming these host cleaning processes.

Question 11

what are p pilli?

Answer 11

group of ahesins in e coli srains that infect kidney, help bacteriaadhere to the kidney epithelial cels

Question 12

how does the adhesin protein bind to the surface?

Answer 12

tip of each pilus is an adhesin protein that bind tightly to a particular glycolipid disaccharide that is found on the surface of kidney cells.

Question 13

What is the responsible quality of the adhesin protein that allows bacteria to colonise a specific area?

Answer 13

the adhesion specificity of the adhesin protein on the tips

Question 14

What is the protection in the stomach?

Answer 14

the thick layer of mucus and perstaltic washing + stomach filled with acid

Question 15

what bacteria can the stomach be colonised by?

Answer 15

Helico pylori

Question 16

bacteria can also produce what?

Answer 16

cytotoxins

Question 17

why do intracellular pathogens have an advantage? and what is the disadvantage??

Answer 17

Advantage is that the pathogens are not accessible to antibodies and not easy targets for phagocytic cells + bathed in rich source of sugars amino acids and other nutrients present in the cytoplasm.
Disadvntage - pathogen needs to require the right mechanisms to enter the host cell and find a suitable subcellular niche where it can replicate + exit cell to continue to spread infection

Question 18

how can bacteria enter a host cell and why is it different to viruses?

Answer 18

Bacteria are much larger than viruses and so cant enter a cell via pores or receptor mediated endocytosis. Therefore they enter via phagocytosis.

Question 19

Phahocytosis is a normal function of macrophages, but what ability have some pathogens acquired?

Answer 19

the ability to survive and replicate within macrophages after they have been phagoctyosed

Question 20

some bacteria cells can invade cells that are nonphagocytic, what are the 2 ways?

Answer 20

the bacteria can express an adhesin that binds with high affinity to a host cell adhesion protein that the host cell normally uses to adhere another host cell or to the extracellular matrix.
the other way is via trigger mechanism . the bacteria injects a set of effector molecules into the host cell cytoplasm through a type 3 secretion system, it initiates a dramatic form of invasion.