Overcome host' defences

Question 1

List the different surface structures which are used to fool or overcome host defence

Answer 1

Surface structures used to fool or overcome host defence
-Stealth
hide in a site which does have much contact with the immune system sequestration eg. the eye
hide within an intracellular location
cover oneself with poor ag
mimic surface structure of host cell
-surface ag variation
change their surface proteins or carbs= angelic variation b4 immune-mediated destruction occurs
-subversion of host’s defence
several surface structure are involved in this

Question 2

How do bacteria survive within intracellular environment

Answer 2

Bacteria which survive within intracellular environment allow themselves to be phagocytosed but they survive and thrive
they do this by using 1 or more of the following
-don’t activate the macrophage
-inhibiting phagosome- lysosome fusion
-resist destruction in the phagosome via murrain in the outer cell membrane
-escape using porins from phagosome

Question 3

Describe how bacteria spread from their site of invasion to the rest of the body

Answer 3

how bacteria spread from their site of invasion to the rest of the body
direct spread of bacteria
-bacteria invading from the outside often spread by extension

Question 4

Lymphogenous spread

Answer 4

Lymphogenous spread
lymph nodes trap bacteria closets to some of bacterial entry, if they are not success in trapping the pathogen they will spread along the lymphatics and will go into the heart and then the blood stream.
If this is occurring the superficial lymph nodes should be checked to see if they are swollen

Question 5

For Haematgoenous list the 2 ways which bacteria spread through out the blood and which animals this will effect the most
common sites of organ localisations

Answer 5

Haematgoenous spread
many bacteria enter the blood stream from any point (respiratory system) causing bacteraemia and their their toxins are present this will cause septicaemia.
This usually occurs in younger animals because their immune system isn fully developed yet
some bacteria enters from the lymphatics for a localised site like the skin and then enter the blood stream via the thoracic duct and spread via the bloodstream, these animals are older
common sties of organ localisation include the joints (when many are affected), brain, meninges and kidneys

Question 6

List way in which a pathogenic bacteria causes damage to tissues or physiological process with the body

Answer 6

how bacteria causes destruction

• direct destruction of cells
• destruction of cells or disruption of physiological processes
• induce a tissue destructive inflammatory response or immune mediated tissue destruction

Question 7

List the steps of direct destruction of cells

6

Answer 7

direct destruction of cells
spore will be phagocytosed, so the bacteria gets inside
-> the acidic environment stimulates the bacteria to become a larger metabolically active reticulate body, so it changes its shape
-> using the hosts’ ATP the bacteria will divide and proven the cell (macrophage) from kill itself
-> in response to inferon gamma the reticulate bodies go tint a dominant phase
-> at the end of the replicative cycle a large no. of bodies (non active) are formed
-> cell can be induced to undergo apoptosis
-> the cell will either rupture or being dead there will be a release of initial bodies, thus making them infectious.

Question 8

For exotoxin 
what produces it 
level of toxicity 
level of specificity and mode of action 
level of ag 
what inactivates it?
-location in bacterium 
composition and structure

Answer 8

exotoxin- produced by gram +ve and -ve by either excretion or lysis
usually potent toxins (only need a small amount to kill the host)
specific action mode of action is similar to enzymes
potent ag
heat activated and inactive by formalin to produce toxoids
location in bacterium outer membrane
-composition and structure; protein

Question 9

For Endotoxin state 
what produces it 
level of toxicity 
level of specificity and what does it stimulates?
-type of ag 
-what destroys it 
-location in bacterium 
-composition and structure

Answer 9

Endotoxin
produced by gram -ve bacteria on bacterial lysis
-less toxic than exotoxin (require a larger amount to do damage)
-less specific than exotoxin and stimulates excessive inflammatory response @ high conc.
-weak ag
-heat stable but destroyed by oxidising agents
location in bacterium within
composition and structure; lipids and carbons

Question 10

Define septicaemia

Answer 10

septicaemia;

presence of bacteria and their products (endotoxin or exotoxin) in bloodstream its blood poisoning

Question 11

Define endotoxaemia

Answer 11

Endotoxaemia
presence of excessive amounts of bacteria lipopolysaccharides in the blood leading to a hyper-inflammatory disorder
its a form of septicaemia but without the bacteria in the blood

Question 12

Explain the functions of the different structures of the endotoxin
(the different part of lipopolysaccharides
-core sugar
-O ag
-lipid A )

Answer 12

functions of the different structures of the endotoxin
LPS- lipopolysaccharides the components are
-core sugars; barrier to macromolecule
-“O” ag: adhere to cell surfaces, if long it will impedes (stop) destruction of bacteria by serum components and phagocytic cells by antigenic shifts
-lipid A; stimulates immune system resulting in a hyper-inflammatory response

Question 13

List the different sources of endotoxin

Answer 13

different sources of endotoxin

• GIT damage/disease
• respiratory tract
• peracute gram -ve mastitis
• other serious gram -ve infections