Micro lab

• Damage to the Cell Membrane


  Can cause smaller molecules to leak out of the bacterial cell and interfere with the active transport and energy metabolism within the cell
• Surface active agents


  • Long chain compounds that are fat-soluble and charged ions that are water soluble
  • Used as disinfectants in homes and hospitals
  • Activity is reduced in the presence of hard water and organic matter
• Cationic agents


  • Detergents where fat-soluble portion is positively charged due to combination with a quaternary nitrogen atom
  • Effective at alkaline pH
• Anionic agents


  • Negatively charged agents that contain long chain hydrocarbons (soaps and bile salts)
  • Remove dirt through the process of emulsification
  • Most effective at acidic pH
• Phenol compounds


  • Act by disrupting cell membranes and causes protein precipitation and enzyme inactivation
  • Act as disinfectants at high concentrations and as antiseptic at low concentrations
• Phenol


  Used as gold standard in the chemical evaluation of new chemical agents
• Cresols


  • Phenol derivatives that more safe and more potent than phenol (Lysol)
• Chloroxylenols


  • Used for topical purposes
  • Effective against gram (+) bacteria
• Hexachlorophene


  • A chlorinated diphenyl which has greater activity against gram (+) bacteria
• Triclosan


  • Organic phenyl ether
  • Activity is good against gram (+) bacteria and a number of gram (-) bacteria
  • Has some activity on fungi and viruses
• Alcohols


  • Disorganize the lipid structure of the cell membrane
  • Dehydrate cells
  • Cause denaturation and coagulation of cellular proteins
• Ethyl alcohol


  • Skin antiseptic
  • Bactericidal
  • Removes lipids from the skin surfaces
• Isopropyl alcohol


  • Greater bactericidal activity than ethyl
  • Less volatile
  • Used to disinfect surfaces
  • Fumes inhalation can cause narcosis
• Benzyl alcohol


  • Used mainly as preservatives
• Methyl alcohol


  • Fungicidal and sporicidal
  • Used to disinfect inoculation hoods