Infection

- presence and multiplication of living organism within host that causes injury
- ** colonization: organism in host that do not cause an injury -- saprophytes (normal flora) or opportunists

- proteins in tissues that cause mis-folding
- protein particles include plaques, tangles, and inclusion bodies
- transmissible neurodegenerative diseases occurr through transplant or eating infected meat (mad cow disease)

- need host
- small, no organelles
- gram positive or negative envelope that provides extra protection
- nucleis acid core that can contain either single or double stranded DNA or RNA

- prokaryotic
- aerobic or anaerobic
- gram positive: have a peptidoglycan cell wall
- gram negative: both peptidoglycan and lipopolysaccharide cell wall
- mycoplasmas: no cell wall because it is inside other cells
- obligate intracellular pathogens: require a host cell

- cocci-spherical: streptocci (chains), staphylococci (clusters)
- bacilli: rods
- spirochetes-helical

- opportunistic
- forms: yeast, mold, or both (dimorphic, which depends on the environment)
- dermatophytes: skin infection, tinea corporis (ringworm), tinea cruis (jock itch), tinea pedis (athletes foot)

- single or unicellular
1) protozoa: unicellular: amoeba (malaria, giardia)
2) helminths: worms (rare in US)
3) arthropods: lice, fleas

modes include skin penetration, direct contact (sexual or in utero), ingestion, inhalation

- exogenous: outside body
- endogenous: from host or on skin
- vector: animal carrying (mosquitos)
- fomite: from object (needle)
- zoonotic: animal spread
**vector carries zoonotic virus**

- subjective + objective data
- stages: incubation, prodrome-initial symdrome (insidious (goes on for awhile), fulminant (prodrome happens quickly))
- acute
- chronic
- convalescent
- resolution

- virulence
- toxins: exotoxin (released from bacteria), endotoxin (cell wall breaking down, gram neg)
- ligand: receptor binding
- capsule: immune evasion; more stable; harder to fight

- culture: most common
- serology (study of serum); host antibodies / titer
- antigen detection: part of bacteria
- nucleic acid sequencing: replicate DNA of infectious agent (PCR)