bmsc210 m2 p7

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bmsc210 m2 p7
2013-04-22 00:07:04
bmsc210 m2 p7

bmsc210 m2 p7
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  1. • Sterilization
    – The killing or removal of all viable organisms within a growth medium
  2. • Inhibition
    – Effectively limiting microbial growth
  3. • Decontamination
    – The treatment of an object to make it safe to handle
  4. • Disinfection
    – Directly targets the removal of all pathogens, not necessarily all microorganisms
  5. • Heat sterilization
    • is the most widely used method of controlling microbial growth (Figure 26.1)
    • – High temperatures denature macromolecules
    • – Amount of time required to reduce viability tenfold is called the decimal reduction time (Figure 26.2)
  6. ___-___ ___ can survive heat that would rapidly kill vegetative cells
    • Spore-forming bacteria
  7. The autoclave
    • is a sealed device that usessteam under pressure (Figure 26.3)
    • – Allows temperature of water to exceed
    • – Not the pressure that kills, but the high temperature
  8. Pasteurization
    • is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
    • – Does not kill all organisms, it is not sterilization
  9. Radiation Sterilization
    • • Microwaves, UV, X-rays, gamma rays can reducemicrobial growth
    • • UV has sufficient energy to cause modifications and breaks in DNA
    • – UV is useful for decontamination of surfaces (Figure 26.4)
    • – Cannot penetrate solid, opaque, or light-absorbingsurfaces
  10. Ionizing radiation
    • – Electromagnetic radiation that produce ions andother reactive molecules
    • – Generates electrons, hydroxyl radicals, and hydride radicals
    • – Some microorganisms are more resistant to radiation than others
    • • Amount of energy required to reduce viability tenfold is analogous to D value (Figure 26.5)
  11. Sources of radiation include ___ and radioactive ___
    • X-rays
    • nuclides
  12. Radiation is used for ___ in the medical field and food industry
  13. Radiation is approved by the WHO and is used in the USA for ___ of ___ particularly susceptible to microbial contamination
    • decontamination of foods
    • • Hamburger, chicken, spices may all be irradiated
  14. Depth filters
    • – HEPA(High-efficiency particulate air) filters
    • -filters that filter though out the medium as opposed to just at the surface. Reduces ability to be clogged
  15. Membrane filters
    – Function more like a sieve
  16. nucleation track (nucleopore) filter
    • -thin polycarbonate films that are perforated by a combined treatment with radiation and chemicals.
    • -work like sieves, preventing the flow of any particle with a size greater than the pore.
  17. bacteriostatic
    • stops cell growth
    • viable cell count=total cell count
  18. bacteriocidal
    • bacteria is killed but not destroyed
    • viable cell count is decreased
    • total cell count stays constant (bacterial cells linger after death)
  19. bacteriolytic
    • bacterial cells are destroyed
    • viable and total cell count drops
  20. Minimum inhibitory concentration (MIC)
    • the smallest amount of an agent needed to inhibit growth of a microorganism
    • – Varies with the organism used, inoculum size,temp, pH, etc.
  21. Disc diffusion assay
    – Antimicrobial agent added to filter paper disc– MIC is reached(bacteria is killed and lawn cleared) at some distance away from disc
  22. Zone of inhibition
    – Area of no growth around filter paper disc
  23. antimicrobial agents can be divided into two categories:
    • – Products used to control microorganisms in commercial and industrial applications
    • • Examples: chemicals in foods, air-conditioning cooling towers, textile and paper products, fuel tanks
    • – Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces
    • • Sterilants, disinfectants, sanitizers, and antiseptics
  24. Cold sterilization
    a process in which sterilization is carry out at low temperature with the help of chemicals, radiations, membranes and all other means excluding high temperature.
  25. Antibiotics
    antimicrobial agents created by organisms naturally
  26. Antimicrobial drugs are classified on the basis of: (3 classifications)
    • – Molecular structure
    • – Mechanism of action
    • – Spectrum of antimicrobial activity(range of microorganisms effected)
  27. selective toxicity
    • -Selective toxicity is ability to inhibit or kill a pathogen without affecting the host
    • -studied by Paul Ehrlich in the early 1900s
  28. Salvarsan
    –one of the first antimicrobial drugs
  29. Growth factor analogs
    • molecules structurally similar to growth factors but do not function in the cell
    • – Analogs similar to vitamins, amino acids, andother compounds
  30. Sulfa drugs:
    • – Inhibit growth of bacteria by use of a paraminobenzoic acid analog (sulfanilamide is thesimplest;
    • -discovered by Gerhard Domagkin the 1930s
  31. Isoniazid
    • a growth analog effective only against Mycobacterium
    • – Interferes with synthesis of mycolic acid (cell wall)
    • effective against: Mycobacterium tuberculosis ect...
  32. Nucleic acid base analogs
    formed by the addition of bromine or fluorine to nucleic acid
  33. Quinolones
    • synthesized antibacterial compounds that interfere with DNA gyrase
    • e.g., ciprofloxacin
  34. DNA gyrase
    supercoiling of DNA in bacteria
  35. semisynthetic Antibiotics
    • -antibiotics that are modified to enhance efficacy
    • – Less than 1% of known antibiotics are clinically useful
  36. B-Lactam antibiotics
    • -one of the most important groups of antibiotics of all time
    • -Named for B-lactam ring
    • – Include penicillins, cephalosporins, and cephamycins
    • – Over half of all antibiotics used worldwide
  37. Penicillins
    (discovered by)
    (effective against)
    • – Discovered by Alexander Fleming
    • – Primarily effective against gram-positive bacteria
    • – Some synthetic forms are effective against some gram-negative bacteria
  38. mechanism of B-lactam antibiotics
    inhibitors of cell wall synthesis, specifically transpeptidation (cross-linking of two glycan-linked peptide chains)
  39. Cephalosporins
    • – Produced by fungus Cephalosporium
    • – Same mode of action as the penicillins (B-lactam ring) but broader range
    • – Commonly used to treat gonorrhea
  40. Aminoglycosides
    • -antibiotics created by Bacteria that contain amino sugars bonded by glycosidic linkage
    • -target 30s sub unit of ribosome
    • -Examples: kanamycin, neomycin, streptomycin
  41. • Neurotoxicity and nephrotoxicity
    • -Antibiotics created by bacteria not commonly used today
    • - Considered reserve antibiotics for when other antibiotics fail
  42. Macrolides
    • -Bacteria synthesized antibiotics that contains lactone rings bonded to sugars
    • Example: erythromycin
    • – Broad-spectrum antibiotic that targets the 50S subunit of ribosome
  43. Tetracyclines
    • -Bacteria synthesized antibiotics that contain four rings
    • – Widespread medical use in humans and animals
    • – Broad-spectrum inhibition of protein synthesis
    • – Inhibits functioning of 30S ribsomal subunit
  44. Antimicrobial drug resistance
    – The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive
  45. six ways that microorganisms can be resistant to an antibiotic
    • 1 Organism lacks structure the antibiotic inhibits
    • 2 Organism is impermeable to the antibiotic
    • 3 Organism can inactivate the antibiotic
    • 4 Organism may modify the target of the antibiotic
    • 5 Organism may develop a resistant biochemical pathway
    • 6 Organism may be able to pump out the antibiotic(efflux)
  46. Methicillin-resistant S. aureus (MRSA)
    one of the few pathogens that have developed resistance to all known antimicrobial agents