INHIBITION & DESTRUCTION OF MICROORGANISM BY PHYSICAL AGENTS

Cards (15)

  • Sterilization
    All forms of microbial life including bacterial spores are killed
  • Disinfection
    Pathogenic organisms but not necessarily all microorganisms or spores are destroyed
  • Moist heat under steam pressure
    1. Kills by coagulation of proteins including enzymes and structural protein
    2. Autoclave at 121°C at 15psi for 15-20 minutes to sterilize medical liquids and instruments
    3. Autoclave at 132°C at 15psi for 30-60 minutes to sterilize infectious medical waste
  • Quality control (QC) for sterilization
    • Done to ensure sterilization is effective
    • Uses Bacillus stearothermophilus in vials or spore-strip sets incorporated in autoclave
  • Dry heat
    1. Causes protein oxidation
    2. Hot air sterilization using ovens at 160-180°C for 1.5-3 hours
    3. Used for sterilization of glassware for lab use
  • Nutrient broth
    • Culture medium used for this activity
    • Turbidity indicates growth of microorganisms
  • Procedure
    1. Transfer impregnated filter paper into nutrient broth and incubate
    2. Immerse inoculated nutrient broth in boiling water bath for 30 minutes
    3. Immerse inoculated nutrient broth in 80°C water bath for 30 minutes
    4. Transfer autoclaved and hot air subjected impregnated filter papers into nutrient broth
  • Observation is indicated as turbid or clear
  • Interpretation
    Bacteria were killed or bacteria were not killed
  • Lactose broth with Durham's fermentation tube
    • Selective culture medium
    • Andrade's indicator turns pink in presence of acid
    • Fermentation of lactose produces acid and gas
  • Evidence of bacterial growth after incubation includes turbidity, presence of gas, and change in pH
  • Disinfectants used
    • Lysol
    • 1:1000 Mercuric Chloride
    • Tincture of Iodine
    • 70% Alcohol
    • 3% H2O2
  • Procedure for testing disinfectants
    1. Transfer 1 mL of cultured E. coli to 10 mL of disinfectant
    2. Transfer inoculum from mixture to Lactose broth tube at 5, 10, 15, and 30 minutes
  • Reading of the result notes the presence of gas inside the Durham's fermentation tube
  • Interpretation of the result
    Bacteria were killed or bacteria were not killed at the specific time