Agents of Infectious Disease Flashcards
Define pathogen
Disease-causing microorganisms
What are commensal organisms?
One organism benefits, other is uninjured
What are opportunistic pathogens?
Normally innocuous unless in an inappropriate location
Define pathogenicity
The ability to induce cellular or tissue damage
Define virulence
A measure of pathogenicity
Describe extracellular infections
Those that anchor to epithelial surfaces, often secrete toxins
Describe intracellular infections
Those that use the cell’s resources to reproduce, cause chronic disease and mostly require cellular death to overcome
List agents of infectious disease
- bacteria
- fungi
- parasites
- viruses
Compare gram positive and gram negative bacteria
Gram positive: thick peptidoglycan wall, retain violet color
Gram negative: thin cell wall, 2 plasma membranes, turns pink with staining, has a lipopolysaccharide extending out from the outer membrane, is an endotoxin because it can cause a heightened immune response, more resistant to antibiotics
What are fungi?
Eukaryotes, single-cell yeast or multicellular, filamentous molds
What are the two major classes of parasites?
Eukaryotes, either protozoan or helminth (worms)
How do protozoa infect humans?
Bites from infected flies or mosquitos
How do helminths infect humans?
Helminth infections result from oral or transdermal transmission, which can lead to chronic infections
Describe viruses
Tiny, infectious, cannot metabolize or independently reproduce, making them obligate intracellular pathogens
Explain how a virus works
The virus enters the cell, sheds an outer protein coat, releases its genome, replicates with cellular replication machinery, exits the cell, leaving it disabled or dead
