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Renin Angiotensin Mechanism.

Disinfection: Introduction & Classification of Disinfectants.

 

Introduction:

  • Disinfection is a process of removal or destruction of microorganisms and reducing their number to a non harmful level.

  • Disinfection usually kills the vegetative form of microorganisms and doesn't affect the endospores.

  • The chemical which is used for disinfection of the nonliving objects (Inanimate objects) is called a “Disinfectant”.

  • The chemical which is used for disinfection of the living objects is called an “Antiseptic”.

  • Mostly the disinfectants are “Bactericidal” while some may be “Bacteriostatic”.

Ideal properties of Disinfectants:

  1. Economical.

  2. Easy to use.

  3. Non toxic.

  4. Broad Spectrum.

  5. Compatible with surface in use.

  6. Odourless.

  7. Fast action.

  8. Good solubility / miscibility.

  9. No impact of physical factors.

  10. Good stability.

Classification of Disinfectants:

  1. Acids and Alkalis.

  2. Alcohols.

  3. Aldehydes.

  4. Detergents and Soaps.

  5. Dyes.

  6. Halogens.

  7. Heavy Metals.

  8. Phenol and derivatives.

  9. Quaternary Ammonium Compounds.


  1. Acids and Alkalis:

  • Acids produce their germicidal action by their capability to produce H+ ions.

  • Some weak acids generate H+ ions enough for generating germicidal action only and not much e.g. Benzoic acid, Salicylic acid etc.

  • Alkalies produce their action by generating “OH- ions”.

  • Only weak acids and alkalis are used as disinfectant as strong acids and alkalis are corrosive in nature.

  1. Alcohols:

  • They possess rapid bactericidal action.

  • Mechanism of Action: They act by denaturation of microbial proteins and causing dehydration.

  • Alcohols are also known to damage lipid blocks present in microbial cell membranes.

  • Ethyl Alcohol (60-70%) is the most commonly used disinfectant from this class.

  • Higher alcohols (Butyl Alcohol, Isopropyl Alcohol, Amyl Alcohol) are stronger in disinfectant action than ethyl alcohol.

  • Isopropanol is used in lower concentration that Ethanol i.e. 50-60% v/v.

  • Alcohols are commonly used to disinfect the skin prior to the hypodermic injections.

  • Alcohols above 60% concentration are found useful against viruses.

  1. Aldehydes:

  • Formaldehyde and Glutaraldehyde are commonly used members from this class.

  • Formaldehyde is used in both gaseous as well as in liquid state.

  • Mechanism of Action: The mechanism of action of Formaldehyde is supposed to be forming cross linkings with amino acids present on cell membrane and protein precipitation.

  • Formaldehyde has a pungent odour and causes irritation to the eyes.

  • Glutaraldehyde is less toxic and less irritant and possesses rapid sporicidal and tuberculocidal actions.

  1. Detergents and Soaps:

  • They are widely used as Surface active agents, wetting agents and as emulsifiers.

  • They are mainly categorized in the following categories,

    • Anionic Surfactants.e.g. Soaps, Sodium Lauryl Sulphate.

    • Cationic Surfactants.e.g. Cetrimide, Benzalkonium chloride.

    • Non-ionic surfactants: No antibacterial action.

    • Amphoteric surfactants.e.g Tego Compounds.

  • Cationic Surfactant are the most effective members from this class.

  • Mechanism of Action: They form bondings with lipid members from cell wall and result in lysis of cell.

  • Soaps prepared from saturated fatty acids are effective against Gram negative bacterias. While soaps prepared from unsaturated fatty acids are effective against Gram positive bacterias.

  1. Dyes:

  • Basic dyes are more effective than acidic dyes.

  • Mechanism of Action: They act by inhibiting cellular oxidation process.

  • Triphenyl methane and Acridine dyes are potent members from this class.

  • Acridine dyes e.g. Proflavine, Aminacrine, Enflavine etc. act by demolishing DNA complexes of microbes and commonly used in treatment of burns and in ophthalmic applications and bladder irrigation.

  • Triphenylmethane dyes e.g Crystal violet, Brilliant green, Malachite green act by inhibiting microbial cellular oxidation process.

  1. Halogens:

  • Chlorine, Fluorine, Bromine and Iodine have strong antibacterial action.

  • Fluorine, Bromine  are well known irritants and hence not used as disinfectants.

  • Iodine is comparatively safer and hence used.

  • Chlorine is specially used for disinfection of water, its germicidal action is due to formation of Hypochlorous acid when it reacts with water.

  • Chlorine acts by combining with cellular proteins and bacterial enzymes making them ineffective.

  • Uses of Chlorine: Disinfection of water, dairy equipment, eating utensil cleaning, disinfection of open wounds, athlete’s foot.

  • Iodine is sporicidal, fungicidal and virucidal.

  • Iodine is a strong oxidizing agent and causes inactivation of microbial proteins.

  • Iodine is combined with surfactants like (Polyvinyl Pyrrolidone) to form compounds called “Iodophors”. Iodophors are non irritant, non staining and odorless compounds.

  1. Heavy Metal:

  • Mercury, Silver and copper compounds are common members from this group.

  • They act by combining with microbial proteins causing denaturation.

  • The common compounds used are,

  • Mercury: Concentration (1:100 / 1:1000)

    • Mercuric chloride, Mercuric oxide., Metaphen.

  • Silver: Concentration ( 1:1000)

    • Silver Nitrate, Organic Colloidal Silver: Argyrol, Collargol.

  • Copper: 

    • Copper Sulphate, (Fungicide, prevents algae growth in swimming pools.)

  1. Phenol and derivatives:

  • Used by Lister in 1867 for first antiseptic surgery.

  • It is obtained by distillation of coal tar.

  • It has strong antimicrobial action and is used as a standard in evaluation of the efficiency of other disinfectants.

  • Mechanism of Action : They cause precipitation of cellular proteins and inactivation of bacterial enzymes.

  • Cresol becomes more potent than phenol when mixed with soap, popular brand Lysol is nothing but a cresol in a soap solution.

  1. Quaternary Ammonium Compounds:

  • Most Cationic Surfactants are Quaternary Ammonium Compounds.

  • Mechanism of Action: Disruption of cell wall and membrane, inactivation of cellular proteins.

They are effective against bacterias, fungi and certain protozo
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