Bacterial Host-pathogen Interaction

Question 1

What is infectivity

Answer 1

Ability to colonise and cause infection in host organism

Question 2

What is pathogenicity

Answer 2

Ability to produce disease in a host organism

Question 3

What is virulence

Answer 3

A term which refers to severity of disease

Question 4

What is host-pathogen interaction

Answer 4

How pathogens (bacteria) sustain themselves and cause disease within host

Question 5

Host pathogen interaction levels

Answer 5

Population
Individual
Cellular/molecular

Question 6

Outcomes after pathogen exposure

Answer 6

• clearance of pathogen
• pathogen colonising / replicating in host

Question 7

What influence whether or not pathogen will colonise in host

Answer 7

• co infection
• genetic factors
• hygiene
• occupational hazard
• pathogens ability to avoid immune detection
• pathogens ability to adhere to cells
• pathogens ability to avoid innate immune response
  -pathogens ability to undergo stress

Question 8

Does pathogen colonisation always lead to disease

Answer 8

No

Question 9

2 main variables that influence outcome of exposure to a pathogen

Answer 9

• ability of pathogen to colonise and cause host damage
• immune status of host

Question 10

What is commensal bacteria

Answer 10

Commensal bacteria are microorganisms that live in or on the body of a host organism without causing harm or disease.

Question 11

Benefits of commensal bacteria

Answer 11

Protection against pathogens
Production of nutrients

Question 12

Key abilities of pathogen

Answer 12

Transmit between hosts
Colonise host
Cause host damage

Question 13

Direct contact

Answer 13

Skin-skin ~ Staphylococcus aureus
Sexual intercourse ~ Neisseria gonorrhoea

Question 14

Indirect contact

Answer 14

Aerosol ~ Mycobacterium tuberculosis

Inanimate objects ~ Salmonella enterica, Vibrio cholerae

Vectors ~ Borellia burgdorferi

Question 15

How are bacteria recognised by host innate immune system

Answer 15

PAMPS are recognised by PRRs!

Toll-like receptors (TLRs): TLRs are proteins that are expressed on the surface of immune cells and recognize specific molecules, such as bacterial lipopolysaccharides (LPS) and flagellin, which are associated with bacterial cell walls and flagella, respectively.

NOD-like receptors (NLRs): NLRs are intracellular receptors that recognize bacterial components, such as peptidoglycan and bacterial DNA, that are released into the host cell cytosol.

Complement system: The complement system is a group of proteins that can directly recognize and bind to bacterial surfaces, leading to the destruction of the bacteria by phagocytic cells.

Phagocytic cells: Phagocytic cells, such as macrophages and neutrophils, can recognize and engulf bacteria through various receptors, such as complement receptors and Fc receptors, which bind to antibodies that have been produced against the bacteria.

Question 16

What are PAMPS

Answer 16

PAMPs, or pathogen-associated molecular patterns, are conserved molecular structures that are associated with pathogens

Question 17

Examples of PAMPS

Answer 17

Peptidoglycan
Lipoproteins
DNA
Flagellin

Gram- only
Lipopolysaccharides

Gram+ only
Wall teichoic acids (WTA)
Lipoteichoic acid (LTA)

Question 18

How are PAMPS recognised

Answer 18

PAMPs are recognized by pattern recognition receptors (PRRs) that are expressed on various immune cells, including macrophages, dendritic cells, and natural killer cells.

Question 19

What are Pattern recognition receptors (PRRs)

Answer 19

Pattern recognition receptors (PRRs) are a family of proteins that are expressed by various cells of the innate immune system

When PRRs recognize PAMPs on the surface of pathogens, they activate downstream signaling pathways that lead to the production of cytokines, chemokines, and other molecules that recruit immune cells to the site of infection and activate them to eliminate the pathogen.

Question 20

Different types of PRRs

Answer 20

Toll-like receptors (TLRs): TLRs are a family of transmembrane proteins that recognize a wide range of PAMPs, including bacterial lipopolysaccharides, flagellin, and viral nucleic acids. There are 10 different TLRs in humans, and they are expressed on various cell types, including immune cells, epithelial cells, and endothelial cells. Upon activation, TLRs trigger downstream signaling pathways that lead to the production of pro-inflammatory cytokines and chemokines, as well as the upregulation of co-stimulatory molecules on antigen-presenting cells.

NOD-like receptors (NLRs): NLRs are cytoplasmic receptors that recognize intracellular PAMPs, such as bacterial peptidoglycans and viral RNA. NLRs form inflammasomes, which are multi-protein complexes that activate caspases and lead to the secretion of pro-inflammatory cytokines, such as IL-1β and IL-18.

RIG-I-like receptors (RLRs): RLRs are cytoplasmic receptors that recognize viral RNA and trigger downstream signaling pathways that lead to the production of type I interferons (IFNs) and pro-inflammatory cytokines. RLRs are important for the detection of RNA viruses, such as influenza and hepatitis C.

C-type lectin receptors (CLRs): CLRs are a family of transmembrane receptors that recognize a wide range of PAMPs, including fungal cell wall components and viral glycoproteins. CLRs are expressed on dendritic cells, macrophages, and other immune cells, and they play a critical role in the recognition of fungi and viruses.

Question 21

What do Toll like receptors recognise

Answer 21

recognise a wide range of PAMPs, including bacterial lipopolysaccharides, flagellin, and viral nucleic acids.

Question 22

What do Nod like receptors recognise

Answer 22

recognise intracellular PAMPs, such as bacterial peptidoglycans and viral RNA

Question 23

What do RIG-1 like receptors recognise

Answer 23

recognise viral RNA

Question 24

What do C-type lectin receptors recognise

Answer 24

recognise a wide range of PAMPs, including fungal cell wall components and viral glycoproteins.

Question 25

Where are TLRs commonly found

Answer 25

Outside of macrophages

Question 26

What PRRs are both transmembrane proteins

Answer 26

CLRs - plasma membrane
TLRs - plasma membrane or in endosomes

Question 27

What PRRs are cytoplasmic sensors

Answer 27

NLRs
RLRs