M5: T3: Disinfection

• factors influencing use of disinfection

  • activity of disinfectant
  • types of material to be treated
  • time of exposure
  • cost
  • []
  • physical and chemical charactersics
• 6 types of disinfections

  1. alklayting agents: aldehydes and ethylene oxides, proteins and DNA for hospitals
  2. alchols: ethanol and isopropyl, target cell membrane, lipi and denature proteins, surface and skin
  3. phenolic compounds: solublise lipids, inactive enzymes, surfaces
  4. halogens
  5. benzalkonium chloride: distrusts lipids in cell membrane and denature proteins, households, surfaces and factories
  6. others: heavy metals, preservatives and natural products
• what affects does heavy metals have

  mercury: inhibit proteins binding them and inhibits microbe growth

  sliver: destroy cell membrane
• why do we use 70%

  1. 100% evaporates too quickly
  2. 100% too strong
  3. 100% can coagulate proteins = shell on surface and prevents alcohol to penetrate
• compare 3 types of measuring anti-microbial activity

  1. tube dilution: determine smallest amount of anto-mic agent to kill microbe, MIC and TGA

  2. agar plate

  3. phenol coefficient: usually inoculated with salmonella typhi, samples removed at 2.5 min intervals
• if the value is higher than 1 


  weaker than phenol