6. Microbiology and intugementary System Flashcards
3 components of host-microbe infection
Host ➡️ environment ➡️ microbe
Commensalism
One species lives in or on the body of another
Mutualism
Reciprocal benefits for both organisms
Parasitism
Only the parasite benifits
Fact: host-pathogen interaction does not always result in disease
- many microbes, infection only caused by a few
- pathogens do not cause disease in every host
- non-pathogens cause disease in most hosts
What is needed to initiate infection
Exposure ➡️ adherence ➡️ invasion ➡️ infection
Further exposure (leading to tissue damage):
➡️Toxicity (toxin effects are local or systemic)
➡️invasiveness (further gross at original and distance sites)
Chain of infection
- Infectious agent
- Reservoir
- Portals of exit
- Modes of transmission (physical, contact, droplet, airborne)
- Portals of entry
- Susceptible host
Living infectious agents
Prokaryotes - bacteria
Eukaryotes - fungi & parasites
Non-living infectious agents
Viruses and prions
Prokaryotes
Bacteria. Has a cell wall with no membrane-bound organelles
Fungi (plant-like)
- Closest relative to humans
- single called (yeast)
- multi-called (mounds/filamentous fungi)
- common features: membrane-bound nucleus and organelles, heterotrophic - enzyme diversity
Protozoans
- Single-called eukaryote with various sub cellular organelles and outer membrane w/o cell wall.
- free-living parasites
- can be classified by their locomotor organelles: amoeba, flagellates, ciliates, sporozoa (non-moving)
Helminths: flatworms
Tape worms (cestodes) Flukes (trematodes)
Helminths - Round Worms
Pinworms, hookworms (nematodes)
What viruses are comprised of
Nuclei acid
Capsid (protein coat)
+/- envelope (lipid)
How viruses obligate intracellular parasites
- Replicate within host cell
- Lack enzymes required for replication and protein synthesis
- specious specific
Prions
Abnormal forms of normal cellular proteins:
- misfolded protein (prion) accumulates in cells disrupting normal functions
- prion protein triggers misfolding of normal proteins = prion replication
How do prions emerge?
Sporadic
Inherited
Acquired (transmission or consumption)
Reservoirs
Where microbes persist:
- human
- animal
- non-living (water, soil & biofilms)
Portals of entry and exit
Endogenous: opportunistic pathogens derived from normal regional flora
Exogenous: Pathogens derived from the external environment
Pathogens must gain access to a specific anatomical niche to initiate infection (tropisms)
Vehicle transmission
Airborne
Waterborne
Foodborne
Vector transmission
Mechanical or biological
