Chapter 9 Micro

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Chapter 9 Micro
2011-03-17 08:38:43
Microbiology Terra

Chapter 9 Microbiology
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  1. Sepsis

    Microbial contamination
  2. Aseptic
    • an environment or procedure that is free of contamination by pathogens
    • antimicrobial chemicals, expected to destroy pathogens but not to achieve sterilization
  3. Disinfectant
    non-living surface
  4. Antiseptic
    living tissue
  5. Sterilization
    removal of all microbial life (heat, filtration)
  6. Pasteurization
    for food
  7. Sanitization
    for utensils
  8. Bacteriostatic
    inhibits bacterial reproduction
  9. Effectiveness of antimicrobial treatment depends on:
    • number of microbes
    • environment
    • time of exposure
    • microbial characteristics
  10. Action of antimicrobial agents: Alteration
    • alteration of cell walls and membrane
    • alter permeability
    • breakdown lipid components
  11. Action of antimicrobial agents: Protein damage
    • damage to protein structure
    • disrupts structural proteins
    • denatured enzymes cause a decrease in cellular activity
  12. Action of antimicrobial agents: Nucleic acid damage
    • damage to nucleic acids
    • loss of genetic information leads to a decrease in metabolic activity
    • can produce fatal mutants
    • can halt protein synthesis through action on RNA
  13. The selection of microbial control methods
    • ideally, agents should be:
    • inexpensive
    • fast acting
    • stable during storage
    • capable of controlling all microbial gowth while being harmless to humans, animals, and objects
    • is this feasible? no
  14. Factors affecting the efficacy of antimicrobial methods
    • site to be treated
    • relative susceptibility of microorganism
    • effectiveness of germicides classified as high, iintermediate, or low
    • environmental conditions
    • temperature
    • pH
    • organic material
  15. Phenol coefficient
    • compare other disinfectants and antiseptics to phenols effectiveness at controlling microbes under standardized conditions
    • greater than 1.0=product is more effective than phenol
  16. Use dilution test
    • expose contaminated cylinders to various dilutions of antimicrobial agents
    • incubate cylinder for 48 hours and check growth
  17. Kelsey-Sykes capacity test
    • expose bacterium to suitable concentration of disinfectant
    • return to growth medium and check turbidity
  18. In-use test
    swabs of object are taken pre/post disinfectant and grown
  19. Heat related methods of microbial control
    • effects of high temperatures
    • denaturation of proteins
    • interference with integrity of cytoplasmic membrane
    • disruption of structure and function of nucleus
  20. Thermal death point
    lowest temperature that kills all cells in broth in 10 minutes
  21. Moist heat
    denatures proteins
  22. Pasteurization
    significant number reduction (esp. spoilage and pathogenic organisms) does not sterilize! Destroyed TB.
  23. Classic holding method of Pasteurization
    63° C for 30 min
  24. Flash Pasteurization (HTST)
    72° C for 15 sec. most common in us. thermoduric organisms survive
  25. Ultra high temperature (UHT)
    • 140° C for <1 sec
    • technically not pasteurization because it sterilizes
  26. Dry heat
    • kills by oxidation
    • denatures proteins and oxidizes metabolic and structural chemicals
    • used for materials that cannot be sterilized with or damaged by moist heat
    • flaming of loop
    • incineration of carcasses
    • bird flu
    • mad cow disease
  27. Refrigeration and freezing
    • decrease microbial metabolsm, growth and reproduction
    • chemical reactions occur slower at low temperatures
    • liquid water not available
    • psychrophilic microbes can multiply in refrigerated foods
    • refigeration halts growth of most pathogens
    • slow freezing more effective than quick freezing
    • organisms vary in susceptibility to freezing
    • exceptions: listeria monocytogenes
    • refrigeration: 0-7° C
    • freezing: below 0° C
  28. Physical methods of microbial control by filtration
    • Air filtration uses high efficiency particulate air (HEPA) filters. effectie to 0.3 um
    • Membrane filters for fluids
    • pore size for bacteria: 0.2-0.4 um
    • pore size for viruses: 0.01 um
  29. Osmotic pressure
    • high concentrations of salt or sugar in foods to inhibit growth
    • cells in a hypertonic solution of salt or sugar lose water; cell desiccates
    • fungi have greater ability than bacteria to survive hypertonic environments
  30. Physcial methods of microbial control by radiation
    radiation damages DNA: sterilization of medical equipment and foods
  31. Chemical methods of microbial control
    • affect microbes cell walls, cytoplasmic memebranes, proteins, or DNA
    • effect varies with temperature, length of exposure, and amount of organic matter
    • also varies with pH, concentration, and age of chemical
    • tend to be more effective against enveloped viruses and vegetative cells of bacteria, fungi, and protozoa
  32. Phenol and Phenolics
    • disrupts cell membranes
    • effective in presence of organic matter and remain active for prolonged time
    • commonly used in health care settings, labs and homes
    • pheno (carbolic acid) historical significance
    • phenolics: creosol (lysol)
    • bisphenolics
    • hexachlorophene: pHisoHex
    • triclosan: toothpaste, antibicterial soaps
  33. Alcohols
    • are bactericidal, fungicidal, and virucidal against enveloped viruses
    • ineffective against fungal spores and bacterials spores
    • denature proteins and disrupt cytoplasmic membranes
    • evaporate rapidly and inactivated by organic debris
    • 70%(optimal concentration) more effective than 90%
    • used in hand santizers and cosmetics
  34. Halogens: oxidizing agents
    • intermediate- level antimicrobial chemicals
    • iodine
    • chlorine
    • bromine
    • fluorine
    • iodine: medically used as a tincture or iodophores
    • betadine
    • sodium hypochlorite (bleach)
    • chlorine treatment of drinking water
  35. Oxidizing agents
    • peroxide kill by oxidation of microbial enzymes
    • effective against anaerobic microorganisms of deep wounds
    • hydrogen peroxide can disinfect and sterilize surfaces of objects
    • 3% or higer
    • catalase neutralizes; not useful for treating open wounds
    • staphylococcus aureus
  36. Surfactants
    "surface active" chemicals that reduce surface tension of solvents to make them more effective at dissolving solutes
  37. Heavy metals
    • ions are antimicrobial because they alter the 3-D shape of proteins, inhibiting or eliminating their function
    • low-level bacteriostatic and fungistatic agents
    • 1% sliver nitrate to prevent blindness caused by N gonorrhoeae
    • thimerosal used to preserve vaccines
    • copper controls algal growth in reservoirs, fish tanks, swimming pools, and water storage tanks; interferes with chlorophyll
  38. Aldehydes
    • inactivate proteins by cross-linking with their function groups (-NH2, -OH, -COOH, -SH)
    • compounds containing terminal -CHO groups
    • glutaraldehyde
    • formalin used in embalming and disinfection of rooms and instruments
  39. Bacterialcidal
    kills bacteria
  40. Bacteria subjected to heat or antimicrobial chemicals die at what rate
    A constant rate
  41. How is the antimicrobial efficacy evaluated?
    microbial death rate
  42. Thermal death time
    time to sterilize volume of liquid at set temperature
  43. Autoclave
    • steam under pressure
    • most dependable sterilzation method
    • steam must directly contact material to be sterilized
    • pressurized steam reaches higher temperatures
    • normal autoclave conditions: 121.5 C for 15 min
    • prion destruction: 132 C for 4.5 hours
  44. Ionizing radiation
    x rays, microwave
  45. Nonionizing radiation
    • UV
    • most effective wavelength~260 nm
    • actively dividing organisms are more susceptible
    • used to limit air and surface contamination
    • germicidal lamps
  46. Soaps and detergents
    good degerming agents but not antimicrobial
  47. Quats
    • quaternary ammonium compounds
    • colorless, tasteless, harmless to humans, and antimicrobial; ideal for many medical and industrial application
    • most effective against gram +
    • pseudomonads live in them