Control of Microorganisms

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Control of Microorganisms
2014-11-04 00:24:38
Test Two
Show Answers:

  1. What are the seven types of antiseptics
    alcohols, quarternary ammonia, hydrogen peroxide, formaldehyde, cresol and soaps, salts, iodine solutions
  2. Alcohol
    plasma membrane disruption
  3. Quarternary ammonia
    cell wall disruption
  4. Hydrogen peroxide
    disruption proteins and enzymes, DNA breakage
  5. Formaldehyde
    protein denaturation and cross-linking
  6. Cresol and soaps
    cell wall adn protein disruption
  7. Salts
    • loss of water
    • protein disruption
  8. Iodine solutions
    • cell wall inhibition
    • attachment/ entry blocker
  9. Effect of temperature
    • high: dry heat, moist heat, incineration
    • - canning, pasteurization, tyndallization

    Low: slows down the enzymes and makes them not work
  10. Other physical controls
    • - radiation: DNA/ RNA falls apart
    • - filtration
    • - Water removal
    • - oxygen: obligate anaerobe; you poison them
  11. To Kill or not?
    Antibiotic: an antimoicrobial substance produced by microorganisms

    microbicidal: drugsthat result in death f bacteria 

    microbiostatic: drugs that stop from growing

    selective toxicity: The best antibiotics are thsoe that are more specific/ selective

    Narrow spectrum: few things more targeted versus broad spectrum: lots of things
  12. Cell wall inhibitors
    penicillins and cephalosporins: inhibit crosslinking withint he peptdiglycan backbone of the cell wall

    inhibit bacterial transpeptidase, the crosslinking enzyme. Without a proper cell wall, the cells are subject to autolysis
  13. Mechanisms of antibiotic activity
    • cell wall inhibitors
    • inhibits protein synthesis
    • inhibitors of membrane function
    • dna inhibitors
    • inhibitors of folic acid
  14. Inhibitors of protien synthesis
    • generally target the ribosomes, blocking or interfering
    • shuts down protein synthesis
    • most effective family: aminoglycosides¬†
    • bind the 30S subunit
    • produced by the actinomycetes
    • neomycin, gentamycin, streptomycin
  15. Mechanisms of aminoglycoside resistance
    • no transporter to bring the drug into the cell
    • bacteria produce enzymes to degrade/modify the drug
    • mtated drug binding site on the ribosome
  16. Other protein synthesis inhibitors
    tetracyclines: bind 30s subunit at the site of tRNA and mRNA binding

    chloramphenicol: binds the 50s subunit and interferes with the peptide bond formaiton in the growing polypeptide

    erythromycin: binds the 50S subut, not allowing for the assocation betwen the 30S and 50S
  17. Inhibitors of membrane function
    • polymyxins: branched polypeptides consisting of 10 amino acid residues
    • these molecuels insert into gram negative plasma membranes, causing structural changes leading to the loss of ionic balance as well as leakage and swelling
  18. DNA inhibitors
    • act by blocking the normal replication of DNA
    • most of these drugs interfere with DNA gyrase
    • protein synthesis continues as normal
    • instead of dividing, these cell form elongated tubes
  19. Folic acid inhibitors
    sulfa drugs: if the drug is incorporated into folic acid, teh resulting molecule is not functional
  20. Folic acid inhibitors
    completely stop DNA/ RNA synthesis

    inhibits formaiton of tetradihydrofolic acid, a precursor of the synthesis of the purines and the pyrimidines
  21. Toxins
    endotoxins: structural component of gram negative bacteria/ released upon cell lysis (large dose get effective change in person)

    exotoxins: in gram positive and gram negative/ species specific/ secreted (small dose to elicit physiological change)
  22. Lipopolysaccharide A (LPS)

    - Highly __
    - toxic effect due to __
    - lipid A is exposed when __
    potent endotoxin

    • lipid moiety termed lipid A
    • gram negative cells are lysed
  23. Lipopolysaccharide A (LPS)

    - causes __

    - in all __

    most gram negative do what??
    a variety of physiological changes

    gram negative bacteria

    secrete exotoxins too
  24. exotoxins
    - proteins
    • most are readily heat inactivated; some are not
    • secreted from bacterial cell
  25. Exotoxins:
    - extremely __
    potent toxins
  26. Classified according to __.
    their site of action

    • nerve: neurotoxin
    • gut: enterotoxin
    • cell: cytotoxin
  27. __ of the toxins.
    alpha and beta portions

    alpha portion enters the cell and elicits the response

    beta portion bidns the cell

    alpha portion generally inactivates a protein in the target cell