C2 Flashcards
How pathogen cause diseases
- Portals of entry
- Penetration of evasion of host defenses
- Damage to host cells
- Portals of exit
Example of portal of entry
- Mucous membrane
- Skin: hair follicles, sweat glands
- Parenteral route:deeper tissue beneath skin
Most common portal of entry for pathogen in mucous membrane
- Respiratory tract
- GI tract
- Genitourinary tract
- Conjunctiva
Explain number of invading microbes
- Likelihood of diseases depends on size of inoculum
- Least no of pathogen to causes infection, more virulent
Define adherence
Capability of pathogenic microbes to attach to cells of body using adhesion factor
Explain specific adherence
- Have adhesin or ligands that bind to host receptors
- Complimentary to host receptors
- Adhesion: glycoprotein, lipoprotein located in capsule, fimbriae, pili, flagella
Explain biofilm as adhesion factor
- Produce glycocalyx that contributes to EPS
- Allow biofilm attach to surface
- Makes it harder for host to remove pathogen
- Provide protection against immune & antibiotic
Define invasion of host cell
Spreading of pathogen throughout local tissues or body
Types of mechanism for host invasion
- Capsule
- Cell wall component
- Enzymes
- Antigenic Variations
- Penetration into host cytoskeleton
Example of cell wall components for host invasion
- M protein
- Fimbriae & Opa
- Mycolic acid
Types of enzymes for host invasion
- Coagulase
- Kinases
- Hyaluronidase
- IgA proteases: destroy host IgA antibody
Explain antigenic variation
- Pathogen alter its surface antigen
- To escape attack by antibody & immune cells
Explain penetration into host cytoskeleton
- Use host actin to penetrate & move into cell actin
- Use actin to penetrate intestinal epithelium
- Produce invasin to rearrange actin to allow bacteria to enter into cell by causing cell membrane wrap around microbe
Mechanism of bacteria that use actin to spread to another host cells
- Bacteria ingested through phagocytosis
- Reside in phagosome
- Lyse the phagosomal membrane
- Escape into cytoplasm & divide
- Induce actin polymerisation at one end
- Form scaffolding- propel bact into cytoplasm
- Released into cytoplasm
Types of infections
- Local
- Focal
- Systemic
Explain local infection
- Infection confined to small area of body
- Near portal of entry
Explain focal infection
Localised pathogen or toxin spread to secondary infection
Explain systemic infection
Infection become disseminated throughout the body
Opsonin induce
Phagocyte to phagocytose (substance that opsonin bound)
How pathogen cause damage to host cell
- Use host nutrient
- Direct damage
- Production of toxin
Explain of host nutrient
- Iron essential for bacterial & human growth
- Human produce transferrin, hemoglobin & lactoferrin
- Iron chelators: bound to iron
How pathogen use iron to damage tissue
- Synthesis iron chelators called siderosphores
- Able to compete with host iron chelators to bring iron into bacterium
Explain direct damage
- Growth & replication in host cell
- Result in host cell lysis
- Penetration through host cell causes damage
Types of toxin
- Exotoxins
- Endotoxin
Explain exotoxin
- Produce inside bacteria as part of their growth
- Toxin gene found on plasmid
- Soluble in body fluids
Function of exotoxin
Destroy certain host cell parts or inhibit particular metabolic function
Types of exotoxin
- Superantigens/ Type I toxin
- Membrane disrupting toxin/ Type II toxin
- A-B/ Type III toxin
Explain superantigen/ Type I toxin
- Bind to host surface but not translocated into cell
- Cause proliferation of T cell
- Induce cytokines
- Excessive cytokines produce symptoms
Explain membrane disrupting toxins/ Type II toxin
- Disrupting eukaryotic cell membrane- lysis
- Some are pore forming toxin
- Some disrupt membrane by producing phospholipase & disrupting phospholipids portion of host cell membrane
Example of pore forming toxin
- Leukocidin: white blood cell
- Hemolysin: red blood cell
Explain Type III toxins
- Exotoxins
- Consist of 2 part (both are polypeptide)
- A: active component - inhibit cell activity
- B: bind surface receptors to bring A into host
- Eg: botulinum, tetanus & cholera
endotoxins consist of
- Glycolipid
- LPS macromolecule
- 75% of outer membrane of Gram -ve bacteria
- Cause lethal shock
Glycolipid & LPS associated with what in endotoxin
- Lipid A: Toxicity
- Polysaccharide: Immunogenicity
Mechanism to expel pathogen from respiratory tract
- Coughing
- Sneezing
Mechanism that transport pathogens out of other portals of exit
- Secretions
- Excretions
What is the example of vehicles for pathogen to leave body
- Feces
- Urine
- Vaginal secretions
- Sweats
Blood borne diseases exit via
Insect/ Vector
Respiratory infection utilize what organ as portals of exits
- Mouth
- Nose
GI infection exit via
Feces or urine
STD exit via
- Urethra
- Genital region
