Chemical Agents and the Control of Microbial Growth

Chemicals that kill or inhibit the growth of microorganisms include chemical preservatives and antiseptics, as well as drugs used in the treatment of infectious diseases of plants and animals. Antimicrobial agents fall into two main categories based on whether or not they are safe for application to mucous membranes.  Concentration of the compound is important to keep in mind when making this distinction.

  • Antiseptics are chemicals that can be applied to the skin and mucous membranes.  Examples include mercurials, silver nitrate, iodine solution, alcohols and detergents.

  • Disinfectants kill microorganisms (not necessarily spores) but are not safe for application to the skin.  Examples of disinfectants include chlorine, hypocholrites,  lye, copper sulfate, and quaternary ammonium compounds.

Common antiseptics and disinfectants

Chemical

Action

Uses

Ethanol (50-70%) Denatures proteins and solubilizes lipids Antiseptic used on skin
Isopropanol (50-70%) Denatures proteins and solubilizes lipids Antiseptic used on skin
Formaldehyde (8%) Reacts with NH2, SH, and COOH groups Disinfectant, kills endospores
Tincture of Iodine Inactivates proteins Antiseptic on skin
Chlorine gas Forms hypochlorous acid, a strong oxidizing agent Disinfects water, general disinfectant
Silver Nitrate Precipitates proteins General antiseptic
Mercuric chloride Inactivates proteins Disinfectant, sometimes used as an antiseptic
Detergents (ex. quat) Disrupts cell membranes Skin antiseptics and disinfectant
Phenolic compounds (ex. lysol, hexacholorophene) Denature proteins and disrupt cell membranes Antiseptics at low concentrations; disinfectants at high concentrations
Ethylene oxide gas Alkylating agent Disinfectant used to sterilize heat sensitive objects such as rubber and plastics

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