lecture 21 pathogenesis
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what is an infection
when an pathogen us growing or multiplying in or an host.
when the host is not capable of controlling g microbial activity, this iscalled __
infectious disease
the numbe rof microbes needed to kill the dose
lethal dose
what is the dose that kills 50% of hosts
LD 50
LOWER ld50 =
greater virulence
number of microbes needed to see the signs of infection in 50% of the hosts
ID 50
number of microbes needed to cause an infection
Infectious DOse
what can be said about professional poathogens
alwasy cause diseases
descirbe opportunistic pathogenes
wait for an opportunity to cause disease, like break in barrier, drop in immune system, compromised host
streptococcus pyogenes
strep throat
staphylococcus aureus
skin infections
proprionibacterium acnes
acne
examples of opportunistic pathogen
strep throat, skin infections, acne
two major branches of immunity
Nonspecific mechanisms (Innate immunity) Specific mechanisms (Acquired immunity)
example of innate community
phagocytosis, inflammation
types of acquired immunity
humoral (antibody) cell-mediated (cytotoxic T cells)
what immunity attacks extra-cellular pathogenes
Humoral (antibody mediated), like bloood, lymph
what immunity attacks intra cellular pathogens
cytotoxic T cell.
types of pathogenes
extracellular pathogens intracellular pathogens
what are extracellular pathogens and what do they infect
resid eoutside of the cells and infect typical bacterium
Host defenses for innate immunity
phagocytosis
process of phagocytosis
• phagocytes digest foreign particles • degraded in lysosomes • cause inflammation
what clears bacteria in tack punctured skin
neutrophils and macrophage
host defenses using adaptive immunity
certain phagocytes present bits of what they captured (microbe) to T cells. T cells produce pro-inflammatory molecules.