Chapter 15: How Microbes Cause Disease Flashcards
pathogenicity
pathogen’s ability to cause disease by overriding body’s defenses
virulence
degree of pathogenicity
virulence factors
assist the pathogen to enter a host, evade the host’s defenses, and damage the host cells, and exit the host
portals of entry
1) mucous membranes- respiratory tract, GI tract (food and water ingested), genitorurinary tract, conjunctiva
2) skin- can be infected by hair follicles
3) parenteral route- depost m/os underneath the skin mucous membranes ex. HIV
penetration or evasion of host defences
1) capsule: impair phagocytosis
2) cell wall components: chemical substances
3) enzymes: coagulase, kinase, hyalonidase, IGA proteases
4) antigenic variation ex influenza
5) invasions (rearrange actin filamints in cytoskeleton of host cell- cause ruffling ex salmonella
6) intracellular growth
coagulase
clots fibronitrogen so it can’t heal ex streptococcus
kinase
digest fibrin clots
hyalonidase
hydrolyzes hyaluronic acid (holds all cells together, CT)
IGA proteases
destroys antibodies
damage to host cell
1) slidophores
2) direct damage
3) toxins- endotoxin and exotoxin
4) lysogenic conversion
5) cytopathic effect
slidophores
take iron from host cells/ proteins (transferrin)
exotoxin
proteins produced inside pathogenic bacteria and then are secretes into the surrounding medium
1) A-B toxins (active binding components
2) membrane disrupting (lyse cells)
3) superantigens (intense immune response
endotoxin
portions of LPS part of outer membrane of cell wall and then break apart when cell wall lyses/ breaks apart
portals of exit
same as portals of entry
- mucous membranes- respiratory, GI tract, genitourinary tract, conjunctiva, -skin
- parenteral route
How do pathogens penetrate host’s defenses?
Adhesins or Invasins (glycoproteins or lipoproteins) use to attach to host cell:
- Capsules & cell wall components
- Glycocalyx of Streptococcus mutans: surface of teeth
- Fimbriae in Escherichia coli & Neisseria gonorrhoeae: cells in genitourinary tract
- Tapered end as a hook: Treponema pallidum
- Invasins rearrange nearby host cell cytoskeleton and induce ruffling
How do pathogens evade host’s immunity?
Virulence of some bacteria is aided by:
- Capsule: Impair phagocytosis (S. pneumoniae)
- Waxy layer: resist digestion by phagocytes (M. tuberculosis)
- Coagulase: Coagulate the fibrinogen in blood (S. aureus)
- Kinase: Digest fibrin clots (S. pyogenes, S. aureus)
- Hyaluronidase: Hydrolyses hyaluronic acid that holds together some cells in body (i.e. connective tissue) - Streptococcus spp, Clostridium spp
- Collaginase: Hydrolyzes collagen: Clostridium spp
- IgA proteases: Destroy IgA antibodies (N. gonorrhoeae)
- Antigenic Variation (Influenza virus, N. gonorrhaeae)
toxins are produced and secreted by actively growing cells
exotoxin
host responds by producing antibodies called antitoxin
exotoxin
these toxins may be found in foods but are usually inactiviated by cooking
exotoxin
these toxins may be toxic in very tiny (nanogram amounts)
exotoxin
these toxins may be produced by gram negative or gram positive bacteria
exotoxin
these toxins are often released upon phagocytosis of or death of bacterial cells
endotoxin
these toxins are produced exclusively by gram negative bacteria
endotoxin
These toxins are produced by bacteria but not viruses
exotoxins and endotoxins
