We have previously reviewed the how, the what and the who of disinfection , but in this post we want to look in more detail at how disinfectants work.

There are a number of disinfectants, and manufacturers to choose from, but in this post we are going to look at the mode of action of the major classes of disinfectants. The most authoritative publication in this area is the CDC HICPAC Guidelines for Disinfection and Sterilization  in Healthcare Facilities 2008. A short summary of the major classes of disinfectant and their mode of action can be seen below taken from the HICPAC 2008 Guideline;

 

Disinfectant Agent (Loading Levels) Mode of Action (1)
Alcohols (50-70%) Alcohols typically work by denaturation of proteins.
Bleaches-chlorine containing and sodium hypochlorite (4-6%) Inactivation of microbes by chlorine containing compounds has been thought to work by a variety of methods includingoxidation of sulfhydryl enzymes and amino acids; ring chlorination of amino acids; loss of intracellular contents; decreased uptake of nutrients; inhibition of protein synthesis; decreased oxygen uptake; oxidation of respiratory components; decreased adenosine triphosphate production; breaks in DNA; and depressed DNA synthesis.
Hydrogen Peroxide (<3%) Hydrogen peroxide releases hydroxyl free radicals that;attack membrane lipids, DNA and cellular components.
Iodophors (0.5-5%) Disruption of protein and nucleic acid structure and synthesis due to rapid cell wall penetration.
Quaternary Ammonium Compounds “Quats” (2%)  Inactivates energy-producing enzymes, denaturates cell proteins, and disruption of the cell membrane.
Phenolic Compounds (0.2-3%) Penetrate and disrupte the cell wall and prepcipitate the cell proteins.

As you can see there is a wide variety of modalities of disinfectants, and it is also worth pointing out that these modalities achieve microbiocidal impacts, however those impacts can be affected by a wide range of conditions such as;

  1. Amount of location of microorganisms
  2. Contact time of agent on material
  3. Presence of organic material
  4. Physiological phase of microbes (planktonic or biofilm)
  5. Innate resistance profile of the microbe

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