Classification and Mode of Action of Disinfectants

• Disinfectants are chemical agents used to eliminate or reduce harmful microorganisms on surfaces and objects.
• They are essential for controlling infections and maintaining hygiene in various settings, including healthcare, laboratories, and public spaces.
• Disinfectants can be classified based on their chemical nature and their mode of action.

Classification by Chemical Nature:

• Alcohols

  • Examples: Ethanol, Isopropanol
  • Mode of Action: Denature proteins, disrupt cell membranes.
  • Use: Commonly used for skin antiseptics and surface disinfection.

• Aldehydes

  • Examples: Formaldehyde, Glutaraldehyde
  • Mode of Action: Cross-linking proteins and nucleic acids, leading to cell death.
  • Use: Sterilization of medical equipment and instruments.

• Phenolics

  • Examples: Phenol, Cresols, Chlorhexidine
  • Mode of Action: Denature proteins and disrupt cell membranes.
  • Use: Disinfecting surfaces, particularly in hospitals and laboratories.

• Halogens

  • Examples: Chlorine, Iodine, Hypochlorites (bleach)
  • Mode of Action: Oxidize cellular components, including proteins and nucleic acids.
  • Use: Water disinfection, surface cleaning, antiseptic solutions.

• Oxidizing Agents

  • Examples: Hydrogen Peroxide, Peracetic Acid, Ozone
  • Mode of Action: Produce free radicals that damage proteins, DNA, and cell membranes.
  • Use: Sterilizing medical equipment, disinfecting surfaces, and water treatment.

• Quaternary Ammonium Compounds (Quats)

  • Examples: Benzalkonium Chloride, Cetylpyridinium Chloride
  • Mode of Action: Disrupt cell membranes and denature proteins.
  • Use: Surface disinfectants, antiseptics, and in some sanitizers.

• Heavy Metals

  • Examples: Silver Nitrate, Mercuric Chloride
  • Mode of Action: Bind to proteins and enzymes, inactivating them.
  • Use: Limited due to toxicity; used in some topical antiseptics and preservatives.

• Biguanides

  • Examples: Chlorhexidine, Polyhexanide
  • Mode of Action: Disrupt cell membranes, leading to leakage of cellular contents.
  • Use: Skin antiseptics, disinfectants in medical settings.

• Acids and Alkalis

  • Examples: Acetic Acid, Lactic Acid, Sodium Hydroxide
  • Mode of Action: Alter pH, denaturing proteins and disrupting cell membranes.
  • Use: Food industry, surface disinfection, and cleaning.

Classification by Spectrum of Activity:

1. Broad-Spectrum Disinfectants

   • Effective against bacteria, viruses, fungi, and spores.
   • Examples: Bleach (sodium hypochlorite), Glutaraldehyde

2. Intermediate-Spectrum Disinfectants

   • Effective against bacteria and enveloped viruses but not non-enveloped viruses or spores.
   • Examples: Quaternary ammonium compounds, Alcohols

3. Limited-Spectrum Disinfectants

   • Effective mainly against bacteria and some enveloped viruses.
   • Examples: Phenolics, some aldehydes

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