Adherence, Colonisation and Invasion

Question 1

Virulence steps

Answer 1

contact
adhesion
Invasion
infection

Question 2

adherence

Answer 2

It is the enhanced ability of M to attach to host tissues
-it is neccessary but not suffficient to start a disease
-There are many different receptors coating the P and the tissue where it binds

Question 3

Adhesions

Answer 3

Glycoproteins or lipoproteins found on P surface that enable it to bind to host cells

Question 4

Virus adhesion

Answer 4

Viruses attach to receptor molecules on cell surface, these can be proteins, carbs or lipids
-they have a single primary receptor as well as co-receptor ( HIV-1: CD4 and CCR5, CXCR4)

Question 5

Attachment factors

Answer 5

Low affinity receptors that are involved and facilitate an initial low affinity binding which is initial step

Question 6

Heparan sulfate

Answer 6

-Found in ECM
-Serves as an attachment factor for many viruses, therefore these receptors have low specificity

Question 7

Binding NB

Answer 7

serves to overcome repulsive electrostatic forces

Question 8

Viral receptors

Answer 8

-diverse
-Have own cellular function ( cytomegalovirus binds to epidermal growth factor, EGF is a powerful mitogen)
-Viruses (V) subvert cell receptors/proteins to utilise them to gain entry
-dictate cell tropism

Question 9

E. B binding

Answer 9

S.aureus binding is facilitated via fibrinogen using the N2 and N3 domains of its SDrG adhesion protein
-Opa adhesion proteins of Neisseria species attach to carcinoembryonic antigen related adhesion molecules (CEACAM) on epithelial surface

Question 10

Capsules

Answer 10

It is a thick hydrated polysaccharide-based( or peptide based) coating outside the plasma membrane and celll wall

Question 11

Capsule function

Answer 11

-Sticky and contains specific receptors to facilitate attachment on host tissues
-Capsules found in encapsulated strains of Streptococcus pneumonia protect from phagocytosis

Question 12

Fimbriae, Flagella and Pili

Answer 12

surface protein structures that function in attachment
-pili are longer and fewer in number than fimbriae
-pili used in horizontal gene transfer (conjugation)

Question 13

Fimrbia and flagella adhesion

Answer 13

-Flagella facillitate adherence to host cells
-Fimbriae possess adhesins which alow for attachment to cells or ECM
-E.coli use them to attach to mannose receptors

Question 14

Colonization

Answer 14

Growth of micro-organisms after they’ve gained access to host tissue

Question 15

Biofilms

Answer 15

A hydrogel composed of polysaccharides, proteins, lipids and DNA that comprises a consortium of bacteria/M that adhere to one another within the gel matrix

Question 16

Biofilm phenotype effect

Answer 16

-B within biofilm are physiologically distinct from planktonic cells
-They are more protected, exhibit communal behaviour
-undergo a phenotypic shift and express/regulate different protein sets
-antibiotic resistance

Question 17

E. biofilms

Answer 17

Pseudomonas aeruginosa are opportunistic P that form biofilms on hospital equipment and on damaged tissue surfaces (burns)

Question 18

Invasion

Answer 18

-Dissemination of a P throughout local tissues or body
-P may produce exoenzymes or toxins which allow them to colonise and damage host tissue as they spread deeper
-P may also produce virulence factors (mainly enzymes) to protect them against immune system defences
-A P’s specific virulence factors determine degree of tissue damage

Question 19

E. specialised enzymes

Answer 19

H.pylori
-Contact with stomach acid keeps the mucin lining the epithelial cell layer in spongy-like state that is impermeable to H.pylori
-B releases urease which neutralises stomach acid by forming ammonia from urea hydrolysis
-This causes mucin to liquify which allows B to swim through it

Question 20

exoenzymes

Answer 20

-Virulence factors that facilitate invasiveness
-Invasiveness requires P to break down host tissues to gain access to deeper or distal tissues
-includes: Hyaluronidase, Coagulase and streptokinase

Question 21

Hyaluronidase

Answer 21

-catalyses the hydrolysis of hyaluronan, a constituent of the ECM which increases tissue permeability
-Other enzymes that degreade ECM include collagenase, chondroitin sulfatase, neuramidase

Question 22

Coagulase and streptokinase

Answer 22

-When staphylococci enter cut, they produce coagulase
-Clot walls off pathogen, blocking access to immune cells
-When P has produced enzymes to fight immune system, streptokinase dissolves clot which release P to bloodstream and deeper tissues

Question 23

Local infection

Answer 23

-Confined to small area of body, typically near point of entry (like boil with staphylococcus)
-P is largely contained to location
-Include urinary tract infections confined to bladder or pneumonia to lungs

Question 24

Focal infection

Answer 24

Localised P and toxins it produces goes to secondary location

Question 25

E. Focal

Answer 25

Bacilus anthraxis or Clostriudium Bascilium

Question 26

Systeminc infection

Answer 26

P spreads throughout body of organism
-E: Yersinia pestis

Question 27

Secondary infection

Answer 27

Primary infection can lead to secondary by another P
eg. influenza and pneomonia

Question 28

Mechanisms of viral spread

Answer 28

-V may remain localised to body surface through which they entered (skin, respiratory tract, intestine, etc)
-Or they can cause generalised infections associated with viremia (V in blood)
-papilloma V cause warts and repliacte in skin epithelia and spread through neighboring cells
-Cells that infect mucosal layer, like coronaviruses, spread in similar way. Infection is limited to mucosa probably due to limited cell tropism in other tissues

Question 29

Lymphatic system

Answer 29

Complex network of tissues, organs and vessels in vertebrates that is part of immune system and complementary to circulatory system
-Lymph nodes, lymphoid organs and lymphoid tissues such as bone marrow make up this system
-excess fluid from blood is carried in lymph to heart

Question 30

V and Lymph

Answer 30

Many V will move from a localised site and disseminate within host, firstly through lymphatic system and then into blood stream and to other organs
-Polio goes from gut to nervous system
-rabies
-smallpox