Control of Microbial Growth

Mechanical Methods
1. Filtration
  1. HEPA
    1. High - efficiency particulate air
    2. use for air in ventilation system
    3. Lower the microbes
    4. Burn units
    5. Laminar flow hood in the laboratory
  2. Millipore filter
    1. Pass fluid through filter with the small pore.
    2. physical separation of bacterial from liquid
    3. Sterilize hear sensitives substance such as antibiotics, serum, hormones
2. Scrubbing
  1. Washing hands with soap and water
  2. physically washing microbes in skin
  3. Sanitizing
Physical Methods
1. Radiation
  1. Ionizing Radiation
    1. water becomes ionized & form reactive hydroxyl radicals
      1. Damage DNA
    2. X-rays, gamma rays
    3. Very penetrating
      1. pass via plastic, glass and packaging
    4. Sterilize
  2. nonionizing radiation
    1. Ultraviolet light
    2. Not as penetrating
      1. need direct contact
    3. Wavelength of 40 - 390nm
2. Temperature
  1. Heat
    1. Moist Heat
      1. Boiling water
        Kills most non-spore forming pathogens
        Does not kill endospore
      2. Pasteurization
        A mild heating method
        Used by Pasteur to kill organisms that caused wine to sour
        Destroys disease causing organisms but not endospores
        Batch Methods
        63° C for 30 min
        Flash Methods
        Rapid cooling
        Does not alter nutrition value
        Lowers bacterial counts
        UHT
        Ultra high- temperature treatments
        134°C for 1-2 sec
        Allow storage of milk without refrigeration
        Sterilized
      3. Autoclaving
        Kills all microorganisms and endospores
        121°C 20 min
        most practiical method
        Used for culture media, surgical equipments, rubber goods
    2. Dry heat
      1. Flaming
        1870°C
        Used inthe lab for loops, test tubes
      2. Incineration
        800°C to 6500°C
        Good for things that have no futher use
        Best method of disposal
      3. Hot -air sterilization in ovens
        Sterilizes
        Used on dry materials, oily substances
        Bulky items require longer times
        150-180°C for 24 hrs
  2. Low Temperature
    1. Cold 5°C
      1. Bacteriostatic
      2. Slow down enzyme action
    2. Freezing -10°C
      1. Bacteriostic, usually not bacteriocidal
      2. Can rupture cells by expandingg water
      3. Prevent spoilage for longer time
3. Dessication
  1. Not effective endospores
  2. Cell remain viable and begain to grow when water is present
  3. lack of water prevents enzyme from working
4. Osmotic Presure
  1. Plasmolysis
    1. Cause water to leave cell
  2. Hypertinic solution
    1. Concentrated salt or sugar solution
  3. inhibits bacterial growtth
Chemical Methods
1. Phenols and Phenolics
  1. First used by Lister Sprayed in
  2. Disrupts plasma membrane
  3. Denatures protein
  4. Inactives enzymes
  5. Triclosan a bisphenol
    1. in antibecterial soaps slowly remove
    2. Broad-spectrum activity and effective against fungi
  6. Chlorhexidine
    1. Chlorine and two phenol rings
    2. An antiseptic used in hospitals
    3. Not sporicidal
2. Alcohols
  1. effective by wiping off dirt and microbes of off sking
  2. Antiseptic
  3. Ethanol 70% most effective and isopropanol rubbing alcohol
  4. Not effective against endospore
  5. dissolves membrane lipids
3. Heavy Metals
  1. Bscteriostatic or bactericidal depending on concentration
  2. Does not kill endospore
  3. Mercury
    1. Thimerosol- antiseptic
  4. Silver
    1. Silver nitrate put into newborns eyes to protect from gonorrhea
    2. Used in dressing and burn creams
  5. Arsenic
  6. Copper
    1. Copper sulfate used to kill algae in water
  7. Selenium
    1. kill fungi
    2. Used to treat skin fungal infection
4. Surfactants
  1. Disrupt the cell membrane
  2. reduce the surface tension of water
  3. Detergents and soaps
5. Peroxygens
  1. Hydrogen peroxide
    1. Poor antiseptic for open wounds
    2. Broken down by catalase to water and oxygen
    3. Used with acidic solutions to steriliz delicate
  2. Ozone o3
    1. reactive form of oxygen
    2. Produce by passing oxygen via electrical discharges
    3. Used to disinfect the air, water, industrial air conditioners, and cooling tower
  3. Disinfectant
  4. Mild antiseptic
6. Halogens
  1. Chlorine
    1. Active ingredient in bleach
    2. can sterilize
    3. Disinfects water
  2. Iodine
    1. Antiseptic
    2. Iodophor
      1. mixed with organic molecule for slow release
        cleanse wounds or prep surgery
        Betadine
    3. dissolve in alcohol
7. Aldehydes
  1. Gluteraldehyde
    1. Kills vegetative cellss and endospore in 3hrs
    2. Good sterilant for heat-sensitive medical equipment
    3. cross-linking with microbial protein
  2. Formaldehyde
    1. Inactive viruses and toxins
    2. Found in embalming fluid
    3. Carcinogen
8. Alkylating Reagents
  1. Denaturing proteins
  2. Ethylene Oxide
    1. Very flammable is mixed with CO2 to reduce fire and explosions
    2. Kills bacteria, endospores, virus, and mold
    3. Sterilizes
    4. Gas at room temperature

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Control of Microbial Growth

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	Created by I Turner over 9 years ago

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