Chemical Disinfectants and Sterilants
Copyright © Charles S. Tritt, Ph.D.
July 26, 1997
Surfactants (including Soaps and Detergents)
Work by physically dislodging and remove microbes, aid in the penetration of other antimicrobial agents and disrupting cell membranes. Cationic (positively charged) surfactants, such as quaternary ammonium compounds or quats, are generally more effective than anionic (negatively charged) surfactants. This is probably due to the net negative charge on the surface of most microbes. Benzalkonium chloride is a quat.
Acids and Alkalis
Work by disrupting tertiary and quaternary protein structures and disturbing charge balances. Acidic solutions often inhibit the growth of fungi. Organic acids such as lactic, propionic, benzoic and sorbic acid are often used as food preservatives.
Alcohols
Work by disrupting tertiary and quaternary protein structures and disrupting membranes. Isopropyl alcohol is the most common, but ethyl and other alcohols are sometimes used.
Phenols
Work by disrupting cell membranes and denaturing proteins. The addition of halogen atoms to phenolic molecules often increases their effectiveness. Example include amylphenol, orthophenylphenol, cresols, hexachlorophene, dichlorophene and chlorhexidine gluconate.
Heavy Metals
Work by interfering with enzyme activity. Examples of heavy metals include selenium (as sulfide), mercury, copper (as sulfate), silver (as nitrate) and Led Zeppelin. Organic mercury compounds such as merthiolate and mercurochrome are often used to disinfect superficial skin wounds. Thimerosal, another organic mercury compound, is used to disinfect both skin and instruments. The organic mercury compounds phenylmercuric nitrate and mercuric naphthenate are used as laboratory disinfectants.
Halogens and Other Oxidizing Agents
Work by disrupting disulfide and other bonds in proteins. Examples of halogens are chlorine, hypochlorous acid (the active ingredient in household bleach), bromine and iodine. Examples of oxidizing agents are hydrogen peroxide (H2O2), ozone and potassium permanganate. One disadvantage of halogens and the other oxidizing agents is that due to the stoichiometric nature of their actions they tend to be ineffective the the presence gross contamination.
Dyes
Work by interfering with DNA replication. Examples include methylene blue and crystal violet (which also works by blocking gram-postive bacterial cell wall synthesis).
Alkylating Agents
Work by disrupting the structure of both proteins and nucleic acids. Specifically they alkylate these molecules. The table below shows the chemical structure of some common alkylating agents
| Formaldehyde | O = CH2 |
| Glutaraldehyde | O = CH - CH2 - CH2 - CH2 - CH = O |
| Ethylene oxide |
O
/ \
H2C --CH2
|
These notes base in part on Microbiology Principles & Applications, 3rd ed. Jacquelyn G. Black. Upper Saddle River, NJ:Prentice Hall. 1996 (ISBN 0-13-230004-4)