目 Mechanism of Action曹 General aspects Sphere of influence Some act locally, killing wbc nearby Others help organism to spread in host itssues by degrading connective tissue Still others are disseminated very far from site where synthesized Diphtheria toxin made in throat, but acts on heart and brain BIOL 533 Lecture 9
BIOL 533 12 Lecture 9 Mechanism of Action • General aspects – Sphere of influence • Some act locally, killing wbc nearby • Others help organism to spread in host itssues by degrading connective tissue • Still others are disseminated very far from site where synthesized – Diphtheria toxin made in throat, but acts on heart and brain
目 Mechanism of Action曹 Level of toxicity Work at extremely low levels; include strongest poisons known 1 g tetanus botulinus or Shiga toxin is enough to kill 10 million people 100-fold more is required for diptheria 1000-fold more for pseudomonas a BIOL 533 Lecture 9
BIOL 533 13 Lecture 9 Mechanism of Action • Level of toxicity – Work at extremely low levels; include strongest poisons known • 1 g tetanus, botulinus, or Shiga toxin is enough to kill 10 million people • 100-fold more is required for diptheria • 1000-fold more for Pseudomonas A
目 Mechanism of Action曹 Mechanisms of damage Lysis of host cells Stop or interfere with cell growth Exaggerate normal physiological mechanisms By depressing or augmenting particular functions, toxins can kill without damaging any cells Tetanus toxin paralyzes body without affecting target neurons Cholera toxin speeds up normal excretory process, resulting in massive loss of water BIOL 533 Lecture 9
BIOL 533 14 Lecture 9 Mechanism of Action • Mechanisms of damage – Lysis of host cells – Stop or interfere with cell growth – Exaggerate normal physiological mechanisms • By depressing or augmenting particular functions, toxins can kill without damaging any cells – Tetanus toxin paralyzes body without affecting target neurons – Cholera toxin speeds up normal excretory process, resulting in massive loss of water
目 Mechanism of Action曹 Toxins that assist bacterial spread in tissues Properties Do not target any type of cell Include degradative enzymes that allow spreading BIOL 533 Lecture 9
BIOL 533 15 Lecture 9 Mechanism of Action • Toxins that assist bacterial spread in tissues – Properties • Do not target any type of cell • Include degradative enzymes that allow spreading
目 Mechanism of Action曹 EXamples: Streptococci Some secrete Hyaluronidase-breaks down hyaluronic acid(connective tissue) DNase-thins out pus made viscous by DNA from dead White blood cell Streptokinase(protease)cleaves precursor of plasminogen activator to active form >> Converts plasminogen to plasmin(serum protease that dissolves fibrin clots BIOL 533 Lecture 9
BIOL 533 16 Lecture 9 Mechanism of Action • Examples: – Streptococci • Some secrete – Hyaluronidase—breaks down hyaluronic acid (connective tissue) – DNase—thins out pus made viscous by DNA from dead white blood cell – Streptokinase (protease)—cleaves precursor of plasminogen activator to active form » Converts plasminogen to plasmin (serum protease that dissolves fibrin clots)