Infection Pathogenesis

Question 1

Virulence Def

Answer 1

Capacity of a microbe to cause disease

Question 2

Pathogenesis Def

Answer 2

Development of disease

Question 3

Realtionship between infection progression and host immune response

Answer 3

Average inividual: immune response should slow disease progression (doe not occur in immunocompromised individuals). Immune response sometimes can hurt host eg liquid filling lungs in Covid

Question 4

How do organisms of low virulence/pathogenicity cause ingredients

Answer 4

host immune system compromised and presence of an anatomical legion

Question 5

Portals of Entry

Answer 5

oral + GIT (ingestion), nasal + respiratory tract (inhalation), skin (penetration), urogenital tract (sexual) and transplacental

Question 6

Virulence factors that allow attachment to host cells (entry to infection)

Answer 6

Pilli, adhesions and biofilm

Question 7

Pilli Outline

Answer 7

Adhesive tips on pathogen flagella that attach to antigens on host cells. Found mostly in gram negative bacteria. Some bacteria can switch pilli allowing access to more host cell binding and escaping detection from immune system

Question 8

Bacterial Adhesions Outline

Answer 8

Protein/glycoprotein molecules on bacterial membrane/fligilli tips

Question 9

Biofilm Outline

Answer 9

Self-produced extracellular polymer matrix typically in eviorments with a lot of shear (eg blood vessels, heart chamber). Bacteria display an altered genotype (microcolony). Biofilm matures overtime. Decreased antibiotic penetration (neutralised) and altered physiology of bacteria in biofil

Question 10

Biofilm Formation

Answer 10

Primary attachment (of single prokaryotic cell), accumulation (of other cells), microcolony formation (biofilm excretion)

Question 11

Most common biofilm infections

Answer 11

Line (medical device) associated (eg pacemakers,urinary cathetars), skin (staph arreus) and soft tissue (open wounds) infections

Question 12

Cystic Fibrosis Biofilm infections

Answer 12

Pseudomonas aeruginosa forms biofilms in bronchi

Question 13

Endocarditis Biofilm infections

Answer 13

Biofilms formed in heart valves

Question 14

Intracellular Pathogens Outline

Answer 14

Bacteria that grow in host cells. Masked from immune system, provided with nutrients and shielded from antibiotics.

Question 15

Virulence that allows pathogens to enter cells

Answer 15

Invasions. Proteins on bacteria surface activates host’s cytoskeleton machinery enabling bacterial entry by endocytosis. Bacteria stays in vesicles

Question 16

How do bacteria prevent phagocytosis

Answer 16

Anti-phagocytic virulence on bacterial cell.

Question 17

Anti-phagocytic Components

Answer 17

polysaccharide capsules (S pnuemoniae and haemophilus influenza), fimbriae (group A streptococci), biofilm (pseudomonas areguinosa), LPS O polysccaride (E Coli) and protein A (s arreus)

Question 18

What virulence can kill white blood cells

Answer 18

leucocidins. Eg S arreus

Question 19

What virulence kills erythrocytes

Answer 19

Hemolysins. E Coli

Question 20

What virulence kills macrophages

Answer 20

Exotoxin A. P aerguinosa

Question 21

How bacterial cells bind to iron

Answer 21

Siderophores bind to iron in proteins allowing them to internalise

Question 22

Endotoxins Outlines

Answer 22

Components on cell membrane that causes damage to host and induce inflammation

Question 23

Exotoxins Outline

Answer 23

Components produced in cell excreted from pathogen to induce inflammation

Question 24

Bacterial Enzymes Outline

Answer 24

Digestive enzymes in cell. Can be weaponised against host cell eg lipase breaks into cell membrane

Question 25

Endotoxin LPS Outline

Answer 25

Lipopolysaccharide. Expressed on membrane of gram negative cells. Contain 2 components O and A. Has pro-inflammatory properties

Question 26

Reaction to gram negative LPS bind to TLR4 receptors

Answer 26

Release cytokines IL6, II8, TNF alpha. Stimulates inflammation, coagulation pathways and complement pathways

Question 27

Characteristics of tolerable inflammation

Answer 27

Low lps. Localised, protective response. Increased permeability and dilation of blood vessels. Defence chemicals and immune cells cane enter tissues. Pathogen is destroyed and removed. Moderate inflammation and fever

Question 28

Characteristics of pathogenic/severe inflammation

Answer 28

High LPS due to high bacterial conc. Risk of intravscular clotting and damage to blood vessels. Results in sepsis. Septic shock (circulatory collapse), respiratory distress, dcreased cardoac output. Organ failure

Question 29

Teichoic acids and lipoteichoic acids, gram positive outline

Answer 29

Binds to TLR2. Releases IL2, II4 and TNF-alpha. Triggers excessive inflammation, intravascular coagulation and tissue damage

Question 30

3 types of exotoxin

Answer 30

A-B toxins, phospholipase and superantingens

Question 31

A-B Toxin Outline

Answer 31

B component brings toxin to cell (by receptor binding stimulated endocytosis) and A component damages cell (by binding to intracellular machinary). Eg C diphtheriae

Question 32

Phospholipase Outline

Answer 32

Breaks down cell membranes. Hydrolysis of phosphatidylcholine and sphingomyelin, resulting in cell lysis eg phospholipase C, C perifinges

Question 33

Superantigens Outline

Answer 33

Proteins excreted from cells. Activate many different types of immune cell by non-specific t-cell activation. Excessive immune response. Uncontrolled release of cytokines. Eg Toxic Shock Syndrome, S aureus

Question 34

3 exotoxins

Answer 34

Cytotoxins (effect cells), neurotoxins (effect neurons) and enterotoxins (cells of the GIT)

Question 35

Clostridium Tetani Toxin Outline

Answer 35

Spores contaminate opening in skin. Spores germinate. Spores can remain latent for up to 10 years and release toxin on lysis. Toxin targets spinal chord and brain stem. Symptoms: trismus (lock jaw), spasms of limbs and trunk, death by respiration complications

Question 36

Clostridium Botulinum Toxin Outline

Answer 36

Spores can be ingested (eg canned foods) or enter through open wounds. Blocks nerve signals to muscles. Results in muscle weakness, paralysis and respiratory failure

Question 37

Cholera Toxin Outline

Answer 37

Produced by vibro cholera (gram negative). Uncontrolled GIT water secretion

Question 38

Bacterial Enzymes

Answer 38

Collagenase, streptokinase, lecithinase, hyaluronidase and urease

Question 39

Collagenase Outline

Answer 39

Breaks down collagen (skin, bone and cartilage) allowing bacterial entry eg C perferinges

Question 40

Streptokinase Outline

Answer 40

Dissolves fibrin clots. Allows bacteria to spread through tissue eg streptococcus pyognes

Question 41

Lecithinase Outline

Answer 41

Breaks down lecithin (cell membrane component) eg listeria

Question 42

Hyrulonidase Outline

Answer 42

Breaks down hyruloric acid (cement between tissues and cells).