Controlling microbial growth

Temperature Based
1. Moist heat
  1. Boiling water
    1. Vegetative bacteria/fungi
    2. Trophozoites
      1. protozoal parasites
    3. Time to kill
      1. ~10 minutes
    4. NOT sterilization
  2. Autoclave
    1. Gold Standard
    2. Steam under pressure
      1. 15 lbs of pressure
      2. Steam @ 121 C
      3. Time = variable
    3. Steam penetration
    4. Bacillus (Geobacillus) stearothermophils
      1. Used to see if autoclave is working
      2. Produces acid and changes color of solution appropriately
  3. Pasteurization
    1. Improve shelf life
    2. Decrease number of pathogens
    3. Maintain quality + nutritional value of products
    4. How?
      1. Batch
        63-66 C for 30 minutes
      2. Flash
        71.6 C for 15 seconds
        Used for dairy products
      3. Ultrahigh temps
        140 C for 1-3 seconds, then rapid cool
  4. Used to
    1. Disinfect
    2. Sterilize
    3. sanitize
    4. pasteurize
  5. more efficient than dry heat
2. Dry Heat
  1. Used in substances that cannot tolerate moist heat
    1. i.e. good for powders
  2. How?
    1. Hot air oven
      1. Denatures proteins
      2. Fosters oxidation
      3. 171 C for 1 hr / 160 C for 2 hrs
    2. Incineration
      1. Complete oxidation
      2. Prions
      3. i.e. bunson burner
        1500 C
3. Lyophilization
  1. Freezing + desiccation
    1. aka freeze-drying
  2. Preservation technique
    1. Foods
    2. Vaccines
    3. bacteria
Chemical Based
1. Phenolics
  1. Derived from phenol
    1. chemically modified to make safer for use
  2. Types
    1. Chlorinated phenolics
    2. Natural phenolics
      1. Pine + clove oils
    3. Bisphenolics
      1. two phenolics linked
    4. Triclosan
    5. Orthophenylphenol
      1. Lysol
  3. Low to intermediate level disinfection
    1. denatures proteins
    2. disrupts membranes
    3. used in clinical settings
    4. can withstand organic contamination
  4. Negatives
    1. Smell
    2. Skin irritant
    3. Hexachlorphene
      1. Prescription only
      2. skin MRSA
      3. Neurotoxin
2. Alcohols
  1. Bacterocidal
  2. Fungicidal
  3. Virucidal (enveloped)
  4. Attacks membranes
  5. Intermediate level
  6. 2 Types
    1. Isopropanol
    2. Ethanol
  7. 70-90% solutions in water are cidal
  8. 100% alcohol is static
  9. Can be toxic
  10. Has high evaporation rate
3. Halogens
  1. Chlorine
    1. Sodium hypochlorite (bleach)
      1. Clinical settings
      2. Must be made fresh bc inactivated in the light/air
    2. Chlorine dioxide (gas)
      1. large spaces
    3. Chloramines
      1. Wound dressing
        Antisepsis
  2. Iodine
    1. Antiseptic
    2. Tincture
      1. Dissolved in 70% alcohol
    3. Iodophor
      1. slow release, like betadine
  3. Intermediate level
4. Oxidizing Agents
  1. High level
    1. Some = antiseptics
    2. Effective against anaerobes especially
    3. Oxidize enzyme systems, block metabolism
  2. Hydrogen peroxide
    1. Surfaces only
  3. Ozone
    1. Reactive form of oxygen (O3)
    2. More expensive than chlorine
    3. Put in drinking water
  4. Peracetic acid
    1. Sporicide
    2. Sterilant of surfaces
5. Surfactants
  1. Low level
  2. Soaps
    1. Amphipathic
    2. Degerming
  3. Detergents
    1. QUATS
      1. NH4 based
      2. Disrupt membranes
      3. Bactericidal
      4. Fungicidal
      5. Virucidal (enveloped)
      6. NOT PSEUDOMONADS
      7. i.e. benzalkonium chloride and cetylpyridinium chloride (in Cepacol mouthwash)
6. Heavy metals
  1. Low level
  2. Limited use today
    1. Allergies
    2. Toxicity
    3. Resistance of microbe
  3. 1% silver nitrate
    1. Newborns, eyes
      1. N. gonorrheae
      2. replaced with abx ointments bc increased risk of STIs
  4. Silver used in wound dressings
  5. Thimerosal
    1. Hg containing
    2. Vaccine preservation.. adults only
  6. Copper used in water systems
    1. controls algae
7. Aldehydes
  1. Glutaraldehyde (liquid)
    1. 2% glutaraldehyde
      1. Sterilant 10 hrs
      2. 10 min = kills bacteria, fungi, viruses
  2. Formaldehyde (gas)
    1. 37% Formaldehyde = formalin
      1. preservative
      2. Disinfectant
      3. strong odor
      4. Carcinogen
      5. Limited use
8. Gaseous agents
  1. Sterilize objects too delicate for heat
  2. Ethylene oxide
  3. Propylene oxide
  4. Beta-propiolactone
  5. 4-18 hr treatment
  6. Attacks crosslinks in protein and nucleic acids
  7. High Hazard
    1. Explosiveness
    2. Carcinogens
9. Enzymes
  1. Lysozymes
    1. Found in human tears
    2. Digests peptidoglycan
  2. Prionzyme
    1. Europe 2006
    2. Removes prions from medical devices

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Controlling microbial growth

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	Created by Connor Clark over 7 years ago