microbio ch 15 pathogenicity

ID50

the number of invading microbes that causes infection in 50% of the population

LD50

concentration of toxin that causes infection in 50% of the population

adhesins

surface projections on a pathogen that allows it to adhere to complementary receptors on host cells

what is the most common receptor for bacterial adhesins

mannose

capsules

slippery layer around bacteria cell walls that allow cells to evade phagocytosis and agglutination

m protein

heat resistant and acid resistant protein in cell surface and fimbriae that improves adherence and helps evade phagocytosis

opa protein

outer membrane protein that helps neisseria gonorrhoeae adhere to and get inside host cells

mycolic acid

waxy lipid in bacteria cell walls that helps mycobacterium tuberculosis resist digestion by phagocytes and multiply inside the phagocyte

coagulase

causing coagulation/clotting, coating microbes in fibrin proteins which conceals them from immune defenses and allows them to replicate

kinase

breaks down blood clots, releasing microbes from the clot to spread

collagenase

breaks down collagen in connective tissue, allowing bacteria to spread

hyaluronidase

breaks down hyaluronic acid in connective tissue, allowing bacteria to spread

IgA protease

breaks down IgA antibodies, allowing them to spread

antigenic variation

ability of a pathogen to change its surface antigens and avoid detection by the immune system

invasins

surface proteins on microbes that rearrange the pathogen's cytoskeleton and allows it to get inside host cells, allowing it to avoid detection and travel between/infect other cells

siderophores

allow bacteria to get iron it needs to replicate from the host

exotoxins vs endotoxins: bacterial source

exotoxins: gram positive and negative bacteria

endotoxins: gram negative bacteria

exotoxins vs endotoxins: relation to microorganism

exotoxins: secreted by microorganisms

endotoxin: present in LPS of cell wall's outer membrane

exotoxins vs endotoxins: effect on the body

exotoxins: specific for particular cells in the body

endotoxins: general effects, including fever and shock

exotoxins vs endotoxins: heat stability

exotoxins: unstable, destroyed at 60-80 C

endotoxins: stable at up to 121 C for an hour

exotoxins vs endotoxins: toxicity

exotoxins: high

endotoxins: low

exotoxins vs endotoxins: fever inducing

exotoxins: no

endotoxins: yes, when released during phagocytosis, stimulates macrophages to release toxic levels of cytokines that cause the hypothalamus to raise the body's body temperature

exotoxins vs endotoxins: immunology

exotoxins: can be converted to toxoids to immunize against toxin

endotoxins: cannot be made into effective toxoids

exotoxins vs endotoxins: lethal dose

exotoxins: small

endotoxins: considerably larger

what is shock?

life threatening decrease in blood pressure

septic shock

shock caused by bacteria

endotoxic shock

shock caused by gram negative bacteria, can result in increased permeability of capillaries resulting in increased leakage of blood, decrease in blood volume/blood pressure, and injury to organs

superantigen

exotoxin that triggers excessive release of cytokines and immune response

skin and soft tissue infection

(methicilin-resistant s. aureus) membrane disrupting exotoxin that makes pores in leukocyte membranes, causing lysis (leukocidin)

gas gangrene and food poisoning

(clostridium perfringens) membrane disrupting exotoxin that:

-targets cells (cytotoxin), resulting in massive hemolysis (RBC destruction)
-targets the intestines (enterotoxin), causing food poisoning/diarrhea

membrane disrupting toxins

exotoxin that targets cell membrane and causes lysis

antibiotic associated diarrhea

membrane disrupting cytotoxin that disrupts host cytoskeleton, resulting in fluid/electrolyte secretion and diarrhea (clostridium difficile)

toxic shock syndrome

superantigen that causes fluid/electrolyte secretion from capillaries, decreasing blood volume and BP

food poisoning

superantigen that causes fluid and electrolyte secretion, resulting in diarrhea (s. aureus)

botulism

A-B neurotoxin that prevents transmission of nerve impulses, resulting in flaccid paralysis (clostridium botilinum)

tetanus

A-B neurotoxin that blocks nerve impulses to muscle relaxation, resulting in uncontrollable muscle contractions (clostridium tetani)

diptheria

A-B cytotoxin that inhibits protein synthesis in nerve, heart, and kidney cells (corynebacterium diphtheriae)

scalded skin syndrome

A-B exotoxin that causes skin layers to separate and slough off (staphylococcus aureus)

cholera

endotoxin that causes fluid and electrolyte secretion, resulting in diarrhea (vibrio cholerae)

traveler's diarrhea

(enterotoxigenic escherichla) A-B enterotoxin that causes fluid and electrolyte secretion, resulting in diarrhea

anthrax

(bacillus anthracis) A-B exotoxin with two A components causes shock and reduces immune response

gastric (stomach) cancer

(helicobacter spp.) A-B genotoxin that causes breaks in DNA