chapter 9 microbiology

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chapter 9 microbiology
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2011-03-08 16:30:13
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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 untensils
  8. other types
    bacteriostatic (inhibits bacterial reproduction), bactericidal (kills bacteria), fungicide, sporicide, germicide
  9. effectiveness of antimicrobial treatment depends on:
    • bacterial populations subjected to heat or antimicrobial chemicals die at a constant rate
    • effectiveness depends on number of microbes, environment, time of exposure, and microbial characteristics
    • evaluation of antimicrobial efficacy:
    • microbial death rate
  10. action of antimicrobial agents
    • alteration of cell walls and membrane
    • alter permeability
    • breakdown lipid components
  11. action of antimicrobial agents
    • damage to protein structure
    • disrupts structural proteins
    • denatured enzymes cause a decrease in cellular activity
  12. action of antimicrobial agents
    • 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 slection 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. the selection of microbial control methods
    • methods for evaluating disinfectants and antiseptics
    • 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. physical methods of microbial control
    • heat related methods
    • effects of high temperatures
    • denaturation of proteins
    • interference with integrity of cytoplasmic membrane
    • disruption of structure and function of nucleus
  20. effects of high temperatures
    • heat is very effective (fast and cheap)
    • thermal death point-lowest temperature that kills all cells in broth in 10 minutes
    • thermal death time-time to sterilize volume of liquid at set temperature
  21. moist heat
    • denatures proteins
    • 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
  22. pasteurization
    significant number reduction (esp. spoilage and pathogenic organisms) does not sterilize
  23. historical goal
    destruction of M. tuberculosis
  24. classic holding method
    63 C for 30 min
  25. flash pasteurization (HTST)
    72 C for 15 sec. most common in us. thermoduric organisms survive
  26. ultra high temperature (UHT)
    • 140 C for <1 sec
    • technically not pasteurization because it sterilizes
  27. 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
  28. 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
  29. physical methods of microbial control
    • air filtration using 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
  30. 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
  31. physcial methods of microbial control
    • radiation damages DNA: sterilization of medical equipment and foods
    • ionizing radiation (x rays, microwave)
    • nonionizing radiation (UV)
    • most effective wavelength~260 nm
    • actively dividing organisms are more susceptible
    • used to limit air and surface contamination
    • germicidal lamps
  32. 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 ceells of bacteria, fungi, and protozoa
  33. 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
  34. 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% more effective than 90%
    • used in hand santizers and cosmetics
  35. 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
  36. 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
  37. surfactants
    • "surface active" chemicals that reduce surface tension of solvents to make them more effective at dissolving solutes
    • soap and detergents
    • good degerming agents but not antimicrobial
    • 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
  38. 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
  39. 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

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