MICROBIAL CONTROL

• Microbial Control


  The control or elimination of microorganisms
• Microbial Control


  • Factors that influence it: Type of microorganisms, Number of microorganisms, Concentration of agent, Presence of organic material, Composition of the material, Time, Temperature, pH, Biofilms
• Outcomes of microbial control

  • Sterilization
  • Disinfection
  • Antisepsis
  • Decontamination

  
• Sterilization


  Eradication of all viable microorganisms including spores

  
• Disinfection


  Eradiation of most microbial life (reduce the numbers... except spores)

  
• Antisepsis


  Disinfection of living tissue (kills or inhibits growth of bacteria)
• Decontamination


  Treatment of inanimate surface to make it safe to handle
• Sterilization with heat


  1. Flaming

  2. Hot air oven (dry heat)

  3. Incineration

  4. Autoclaving (steam under pressure)
• Heat kills living things by denaturing essential proteins
• Sterilization with irradiation


  1. Gamma irradiation

  2. UV light
• Gamma irradiation


  Kills living organisms by breaking down DNA, inhibiting division
• UV light


  Breaks down chemical bonds and scrambles the structure of DNA, RNA and proteins, causing a microorganism to be unable to multiply
• Sterilization with chemicals


  Appropriate for heat-sensitive materials, need desorption to remove toxic residual wastes
• Sterilization by filtration


  Removes, rather than destroys, microorganisms through sieving, adsorption, and trapping
• Prions


  Abnormal, pathogenic proteins that are transmissible and can induce abnormal folding of specific normal cellular proteins
• Prions are not considered a living organism
• Prion diseases in animals

  • Bovine Spongiform Encephalopathy (BSE)
  • Chronic Wasting Disease (CWD)
  • Scrapie
  • Transmissible mink encephalopathy
  • Feline spongiform encephalopathy
  • Ungulate spongiform encephalopathy
• Elimination of prions


  1. Sodium hydroxide (NaOH, 1N) immersion + autoclaving (121°C)

  2. High-temperature autoclaving of 132°C for 1 hour

  3. High-temperature autoclaving of 134°C for 18 minutes
• Disinfection


  Destruction of microorganisms, but not usually spores, on inanimate surfaces or objects

  
• Disinfection methods


  1. Boiling water (100°C)

  2. Pasteurization (72°C, 15-25 s)

  3. UV-light (UV-A & B)

  4. Sun light

  5. Chemical disinfection

  6. Membrane filtration
• Pasteurization


  Rapidly heating liquids (food) to slow microbial growth, while maintaining taste
• Antisepsis


  Destruction or inhibition of micro-organisms on living tissues, thereby limiting or preventing the harmful results of infection
• Microbial control methods


  • Physical: Heat (dry, moist), Cold, Radiation, Filtration
  • Chemical: Gases, Liquids (animate, inanimate)
• Microbial control methods prevent multiplication, but do not remove present microorganisms

  
• Antimicrobial treatment


  Appropriate treatment for acute, severe, persistent, or progressive infectious diseases, depends on accuracy of diagnosis and appropriateness of antimicrobial agent
• Bacteriophages


  High ability to inhibit different wound infections caused by bacteria, heal the wound faster, have lower side effects and toxicity, destroy bacterial biofilm, useful in controlling immune responses
• Hyperbaric oxygen therapy (HBOT)


  Increases oxygen saturation in tissues, enhances the body's immune response, contributes to formation of toxic free radicals that inhibit the growth of oxygen-sensitive or anaerobic bacteria, risk of oxygen toxicity