Pathogenesis: Adhesion Flashcards
Virulence Factors purpose
- Involved in Adhesion of a pathogen
- Involved in Invasion of a host cell
- Involved in Evasion of the immune system
- Involved in host damage caused by a pathogen
Steps in the infectious process
- Adhesion/Entry
- Invasion/Local or General Spread 3. Multiplication
- Evasion
- Damage (pathology/disease)
- Transmission (Shedding)
Outcome of infectious disease
- Host immunity
- Pathogen virulence
Commensals
normal microbiota
Opportunists
bacteria that affects immunocompromised hosts
Primary pathogen
opposite of opportunistic, can infect healthy host
virulent factors
- motility via flagella
- adherence via
- pili
- non-pilus adhesins
pili functions
- Pili enable some organisms to adhere to receptors on target host cells and thus colonize and resist flushing by the body
- other functions
- DNA transfer, phage binding, biofilm formation, cell aggregation and twitching motility
What are pili?
thin, protein tubes originating from the cytoplasmic membrane and are found in many Gram-negative bacteria but not in many Gram-positive bacteria
How do pili adhere?
- Both bacteria and the host cells have a negative surface charge leading to electrostatic repulsion
- The electrostatic repulsion is cancelled out by the protein shaft called pilin and adhesive tip
Pili are classified by what?
their structure and assembly mechanisms
Type I pili species
EPEC (enteropathogenic E. coli)
Type I pili adhesion receptors
glycoproteins and glycolipids (D-mannose component)
Type I pili gene organization
operon
Type I pili functions
- host-tissue adhesion
- co-aggregation
- immunomodulation
- biosensor and biofilm formation
Type IV pili species
E. coli , Salmonella enterica, Pseudomonas aeruginosa, Neisseria meningitides, Neisseria, gonorrheae, Legionella pneumophila, Vibrio cholerae
Type IV pili adhesion receptors
- CD46
- glycolipids
- C4BP
Type IV pili gene organization
pathogenicity island
Type IV pili functions
- host-tissue adhesion
- co-aggregation
- immunomodulation
- motility
- DNA uptake
What are non-pilus adhesions?
Surface proteins found in the cell wall of various bacteria that bind to specific receptor molecules on the surface of host cells
non-pilus adhesins examples
-
Streptococcus pyogenes
- Lipoteichoic acid, Protrein F, M protein (bind to fibronectin, a common protein on epithelial cells)
-
Neisseria gonorrheae:
- Opa protein that enables the bacterium to make a more intimate contact with the host cell after it first adheres with its pili
-
Staphylococcus aureus
- uses protein A as an adhesin
Facultative intracellular pathogens examples
Salmonella, Shigella, Yersinia
Obligate intracellular pathogens examples
Rickettsia, Chlamydia, Coxiella
Extracellular pathogens examples
Vibrio cholerae, Pseudomonas, enterotoxigenic E. coli
