microbiology

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Author:
mattnjaneal
ID:
223931
Filename:
microbiology
Updated:
2013-06-15 11:37:50
Tags:
control microbial growth
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Description:
chapter 11
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  1. sterilization
    remove or destroy all viable organisms includes bacterial endospores
  2. disinfection
    kill pathogens on inanimate object; disinfectant
  3. decontamination
    physical removal by scrubbing the surface.  ex: surgical scrub
  4. sanitization
    reduce the number of pathogens to a safe level
  5. cidal vs. static agents
    • cidal = kill
    • static = inhibit growth
  6. death rate factors
    • microbial load - # of MO
    • MO population make-up
    • pH and temperature
    • intensity of the agent (target):  a)cell wall b)cell membranes c)disrupt nucleic acid d)denature proteins
    • presence of organic matter - can interfere with action.  ex:  removing blood from floor before disinfecting
  7. physical methods to control microbial growth
    • heat
    • pasteurization
    • cold
    • dessication
    • radiation
    • filtration
    • microwaves
    • preservation
  8. thermal death time
    time it takes to kill a population at a given temp; temperature is constant
  9. thermal death point
    set a constant time; minimum temp to kill a population in a given amount of time
  10. types of dry heat treatment
    • dry heat - organic matter removed
    • direct flame - incinerate
    • hot air oven - 160'c for 2 hours; can be used for powders or glassware
  11. types of moist heat treatment
    • boiling - kills many pathogens, disinfects, endospores can survive
    • autoclave - steam under pressure (2ATM); 121'c, kills everything 15-30min., including spores
  12. 2 types of heat treatment
    • dry heat - organic matter removed
    • moist heat - faster and lower temps
  13. pasteurization
    use heat to destroy pathogens and to extend shelf life
  14. 3 types of pasteurization
    • holding method (batch) - 62.9'c hold for 30 min; must stir to equally distribute
    • flash pasteurization - 71.6'c for 15 sec.  less opportunity to destroy nutrients
    • ultra pasteurization - 82'c for 3 seconds
  15. What are the targets of pasteurization in dairy products?
    campylobacter, listeria, and mycobacterium
  16. How does cold help control microbial growth?
    stops or slows microbial growth by decreasing reaction rates
  17. dessication
    • dry or dehydrate
    • AW - activity of water, amount of water available to support life (MO's)
    • ex: lettuce AW = 0.99 (99% water); cracker AW - 0.35 (35% water); the AW in crackers is too low to support bacterial growth
  18. lyophilization
    freeze drying
  19. radiation
    • smaller wavelengths than visible light
    • action: disrupts DNA
  20. 2 types of radiation used to control MO growth
    • UV radiation
    • ionizing radiation
  21. UV radiation
    • causes the formation of thymine dimers
    • used appropriately for surfaces, air, and water
  22. ionizing radiation
    • forming radicals, highly reactive, and disrupt macromolecules in cell including
    • DNA
    • penetrates packaging
  23. filtration
    seperation based on size
  24. types of filters
    • inorganic - porcelain or glass
    • organic fitter - diatomaceous, attracts organic
    • membrane filter - organic compound nitro cellulose
    • HEPA:  high efficiency particulate air filters; 99.9% filters
  25. microwaves
    kill by heating H2O; uneven heating
  26. preservation methods
    • drying - dehydration, removes H2O
    • salting - changes activity of water, decrease AW
  27. chemical control of MO's
    • antiseptics - used on living tissue
    • disinfectants - used on inanimate objects
  28. selection of chemical agents
    • type of MO
    • non-toxic
    • solubility in water
    • shelf life
    • application time
    • temperature - cold vs. warm
    • penetration - surface
  29. How do you evaluate the efficiency of the method used?
    • phenol coefficient
    • in-use test
  30. phenol coefficient
    • phenol value = 1.0
    • disinfectant > 1.0 is better than phenol
  31. Joseph Lister
    pioneered aseptic surgery
  32. in-use test
    • sample surface (ex: bed rails)
    • disinfect and follow up sampling
  33. chemical families
    • halogens
    • phenols
    • chlorhexidine
    • heavy metals
    • alcohol
    • alkylating agents
    • ethylene oxide gas
    • ?
    • surfactants
  34. halogens
    • highly reactive
    • form salts and release ions in H2O
    • react with organic matter and oxidize proteins and other molecules
  35. 2 types of halogens
    • Chlorine (Cl) - both inorganic and organic forms; inexpensive
    • iodine
  36. 4 forms of chlorine
    • chlorine gas (Cl2)
    • hypochlorite
    • chlorine dioxide
    • chloramine
  37. chlorine gas (Cl2)
    • bubble through water supplies to disinfect
    • doesn't kill Giardia or cryptosporidium
    • toxic
  38. hypochlorite
    • sodium or calcium salts
    • 5% Na salt - household bleach
    • drinking water, pools, and waster water
    • bleaches and forms toxic chlorinated molecules
  39. chlorine dioxide
    • for drinking water, pools, and waste water
    • doesn't form toxins
    • safer
  40. chloramine
    • organic
    • doesn't form toxins
    • wound antisepsis
    • long lasting
  41. iodine
    • tincture - 2% iodine in alcohol
    • iodophor - iodine complexed with organic carrier; long term release; betadine, poridine
    • pseudomonas can grow
  42. phenol
    • carbonic acid
    • unpleasant odor
    • irritating to skin and mucous membranes
    • denature proteins
  43. phenolics
    • derivatives
    • 3 types:  cresol, bisphenols, triclosan
  44. cresol
    • derived from coal tar
    • creosote for wood preservative
    • clove oil - antimicrobial and analgesic
  45. bisphenols
    • 2 phenol rings
    • orthophenyl phenol - active ingredient in Lysol
    • hexochloraphene - phisoHex, lotions and used as a surgical scrub; caused neurological damage to infants
  46. triclosan
    • antibacterial soaps and toothpast
    • used in plastic. ex: microban
  47. chlorhexidine
    • safer phenol containing chlorine and 2 phenols
    • antiseptic, milk and low toxicity
    • hibiclens
    • peridex and periogard - oral rinse
  48. 3 heavy metals
    • mercury
    • copper
    • silver
  49. mercury
    • antimicrobial but toxic
    • 4 types: mercuric chloride, mercurochrome, merthiollate, thimerosal
  50. mercuric chloride
    paint additive to prevent mildew
  51. mercurochrome
    • Hg + organic compound
    • antiseptic
  52. merthiollate
    • antiseptic
    • thimerosol
  53. thimerosol
    • vaccine additive
    • banned in US
    • ethylmercury
  54. copper
    • effective against photosynthetic organisms (MO's)
    • algicide
    • copper sulfate - light blue color
  55. silver
    • silvidine - silver sulfadiazine, cream applied to burns
    • silver nitrate - 1% solution; historically used to prevednt gonococcal opthalmia
  56. alcohol
    • more effective when it is diluted
    • isopropyl alcohol
    • ethanol
    • short lived, once evaporated the activity is gone
    • 10 minute soak will sanitize
  57. alkylating agents
    • react with proteins
    • 2 types: formaldehyde, gluteraldehyde
  58. formaldehyde
    • carcinogenic
    • inactivate viruses
  59. gluteraldehyde
    • cidex
    • 10 min soak to disinfect
    • 10 hr soak to sterilize
  60. ethylene oxide gas
    • sterilizer - chamber (like autoclave)
    • if it comes in contact with moisture it will form a toxin
  61. surfactants
    • hydrophobic/hydrophilic end
    • soaps - natural,  like ivory, ionic (negative end)
    • detergents- cationic (positive end), quaternary ammonium compounds
    • ex: zephiran and cepacol (throat)
    • disrupt cell membranes
    • sanitizer

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