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 Antiseptic and Disinfectants  and Their Action
 
 
Chemical Agent Action
Protein Denaturants
Heavy metals:
       Silver: AgNO3 Protein precipitant activity neutralized by organic matter used in eyes of newborns to prevent gonorrhea
       Copper: CuSO4 Kills algae in swimming pools and water supplies. Fungicide for plant diseases, Bordeaux mixture
        Mercury: HgCI2 Combines with -SH groups in proteins Very toxic to humans Used to treat syphilis with serious side effects. Organic mercury compounds still used. e.g.. Mercurochrome
 Halogens:
       Iodine
Tincture of iodine (0.2% I2 in 70% ethanol),
Iodine in solution of KI   (KI3)
Iodophors (I2 complexed with detergents)
Iodinates proteins containing tyrosine residues
antiseptic on skin disinfectant of medical instruments small scale water purification; relatively nontoxic on skin but toxic internally
Betadene is an iodophore (Ps. aeruginosa can live in/on iodophores)
Alcohols:
     Ethanol and Isopropyl alcohol
most active with some water present (50-70% alcohol in water)
Lipid solvents and protein denaturants. Antiseptic on skin. Disinfectant for hospital items
Aldehydes:
     Formaldehyde
HCHO available as 37% solution in water (formalin) used as 2% aqueous solution or as gas for fogging
Alkylating agent combines with -NH2, -COOH, and -SH groups in nucleic acids and proteins. Neutralized by organic matter. Used for embalming of corpses and the small amounts in wood smoke aid smoke to preserve meat 
     Glutaraldehyde,
COHCH2CH2CH2CHO: used as 2% aqueous
solution
Less toxic than formaldehyde. Cold sterilization of hospital goods neutralized by organic matter
      Ethylene oxide
             Used as a gas 
Alkylating agent very toxic, used in special gas
sterilization units for heat sensitive goods e.g. plastic disposable equipment
Phenols:
      Phenol
carbolic acid, C6H12OH used as 5% aqueous solution. Cresol & xylenols also used
Protein denaturant. Disrupts cell membrane at low concentrations. Very toxic, activity increased by soaps, not affected by organic matter. Disinfectant for large, dirty surfaces (Lysol)
Natural polyphenols (tannins) used to preserve hides (tanning)
  Hexachlorophene
a chlorinated biphenol
Once widely used because it persists on skin. Restricted now due to worry about brain damage. Excellent for control of Staphylococcus.
Detergents:
    Soaps
anionic detergents (-ve)
Disrupt microbial membranes ( best for Gram -ve Anionic have only mild action due to repulsion of -ve charged on bacteria and can neutralise many antiseptics
   Quaternary Ammonium Compounds
cationic detergents (+ve)
For effective but not against TB or spores. Used as sanitisers.
Oxidising Agents:
   Hydrogen Peroxide  (H2O2) Relies on production but not reliable
  Chlorine:
In Cl2 gas. Ca(OCI)2 and  NaOCl. the active ingredient is HOCl, and formed at neutral or acidic conditions
Activity is neutralized by organic mater, used in water purification and general disinfectant in food and dairy industries
    Potassium permanganate
(KMnO4) Condies Crystals
Strong oxidising agent. May irritate skin
Dyes & Others
     Gention Violet 1% Inhibit G+ve bacteria and fungi  not G-ve's
      Acriflavin Inhibit G-ve bacteria
     Brilliant Green and Malachite Green Once used for gastro. Rarely used now.
    Lime  Ca(OH)2 Powerful disinfectant. Deactivated by CO2
Dilute solution is whitewash
   Chlorinated lime (bleaching powder) Chlorine liberating disinfectant

Measurement of Antiseptic strength
Antibiotocs