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Alcohols tend to be bactericidal and fungicidal, but may also be viricidal for enveloped viruses only. Although alcohols are not sporicidal, they do inhibit the processes of sporulation and germination. Alcohols are volatile and dry quickly, but they may also cause skin irritation because they dehydrate the skin at the site of application. One common clinical use of alcohols is swabbing the skin for degerming before needle injection. Alcohols also are the active ingredients in instant hand sanitizer s, which have gained popularity in recent years. The alcohol in these hand sanitizers works both by denaturing proteins and by disrupting the microbial cell membrane, but will not work effectively in the presence of visible dirt.

Last, alcohols are used to make tincture s with other antiseptics, such as the iodine tinctures discussed previously in this chapter. All in all, alcohols are inexpensive and quite effective for the disinfection of a broad range of vegetative microbes. However, one disadvantage of alcohols is their high volatility, limiting their effectiveness to immediately after application.

a) Ethyl alcohol has 2 C’s and an OH.  B) Isopropyl alcohol has 3 C’s and an OH.
(a) Ethyl alcohol, the intoxicating ingredient found in alcoholic drinks, is also used commonly as a disinfectant. (b) Isopropyl alcohol, also called rubbing alcohol, has a related molecular structure and is another commonly used disinfectant. (credit a photo: modification of work by D Coetzee; credit b photo: modification of work by Craig Spurrier)
  • Name at least three advantages of alcohols as disinfectants.
  • Describe several specific applications of alcohols used in disinfectant products.


Surface-active agents, or surfactants , are a group of chemical compounds that lower the surface tension of water. Surfactants are the major ingredients in soaps and detergents . Soaps are salts of long-chain fatty acids and have both polar and nonpolar regions, allowing them to interact with polar and nonpolar regions in other molecules ( [link] ). They can interact with nonpolar oils and grease to create emulsions in water, loosening and lifting away dirt and microbes from surfaces and skin. Soaps do not kill or inhibit microbial growth and so are not considered antiseptics or disinfectants. However, proper use of soaps mechanically carries away microorganisms, effectively degerming a surface. Some soaps contain added bacteriostatic agents such as triclocarban or cloflucarban , compounds structurally related to triclosan, that introduce antiseptic or disinfectant properties to the soaps.

A chemical structure with a long carbon chain and two oxygens at one end. The end with the oxygens is the hydrophobic head which shuns hydrocarbon-like substances but is attracted to water molecules. Thi sis the anionic portion of the molecule. The long carbon chains are the hydrophilic tail which shuns water but is attracted to oily greasy hydrocarbon-like substances.
Soaps are the salts (sodium salt in the illustration) of fatty acids and have the ability to emulsify lipids, fats, and oils by interacting with water through their hydrophilic heads and with the lipid at their hydrophobic tails.

Soaps, however, often form films that are difficult to rinse away, especially in hard water, which contains high concentrations of calcium and magnesium mineral salts. Detergents contain synthetic surfactant molecules with both polar and nonpolar regions that have strong cleansing activity but are more soluble, even in hard water, and, therefore, leave behind no soapy deposits. Anionic detergents , such as those used for laundry, have a negatively charged anion at one end attached to a long hydrophobic chain, whereas cationic detergents have a positively charged cation instead. Cationic detergents include an important class of disinfectants and antiseptics called the quaternary ammonium salts (quats) , named for the characteristic quaternary nitrogen atom that confers the positive charge ( [link] ). Overall, quats have properties similar to phospholipids, having hydrophilic and hydrophobic ends. As such, quats have the ability to insert into the bacterial phospholipid bilayer and disrupt membrane integrity. The cationic charge of quats appears to confer their antimicrobial properties, which are diminished when neutralized. Quats have several useful properties. They are stable, nontoxic, inexpensive, colorless, odorless, and tasteless. They tend to be bactericidal by disrupting membranes. They are also active against fungi, protozoans, and enveloped viruses, but endospores are unaffected. In clinical settings, they may be used as antiseptics or to disinfect surfaces. Mixtures of quats are also commonly found in household cleaners and disinfectants, including many current formulations of Lysol brand products, which contain benzalkonium chlorides as the active ingredients. Benzalkonium chlorides, along with the quat cetylpyrimidine chloride , are also found in products such as skin antiseptics, oral rinses, and mouthwashes.

Questions & Answers

full life cycle of plasmodium parasite
Emmah Reply
what are ways of handling sharps
namugenyi Reply
never recap or bend a sharp objects
describe the process of platelet formation
Joy Reply
what is parasitic helminths
Sadiya Reply
list three categories of symbiotic relationships.
mary Reply
what's the difference between microbial intoxication and infectious diseases
dranimva Reply
microbial intoxication results when a person ingests a toxin or a poisonous substance that has been produced by a microbe while infectious disease results when a pathogen colonize the body and subsequently cause disease.
weighing balance is needed in lab of microbiology for weighing?
amna Reply
It is mainly used for media preparation and product testing purpose.
thank you for your joining
what is microbiology
Shamsuddeen Reply
study of living organisms that are too small to be visible with naked eye
microbiology is the study of microscopic organisms, either unicellular(single cell), multicellular( cell colony), or acellular (lacking cell).
is the word Atypical or a typical bacteria. .am confused pliz help
typical bacteria
okay thank you what does that mean
atypical means that it has some characters from bacteria not all characters ...but tybical means that it has all the characters that bacteria have
thank you Zulpha
some examples please
thank you Reham
1) typical bacteria contain a cell wall whereas atypical bacteria usually do not contain a cell . 2) typical bacteria can be either Gram-positive or Gram-negative while atypical bacteria remain colorless with Gram staining. 3) cells of typical bacteria are large ,while cells of the atypical small
Example of atypical : Mycoplasma pneumoniae , chlamydophila pneumoniae , legionella
what is micro biology
Jauharah Reply
is the study of organisms which can't be viewed by our necked eyes
Because it preexisting causing secondary infection after collateral damage of normal microbota
Rafaa Reply
combinations of drugs that can't be taken together and why
Grace Reply
Antagonism: the combined action is less than that of the more effective agent when used alone). All these effects may be observed in vitro (particularly in terms of bactericidal rate) and in vivo والله اعلم
....fermentros have 1-15litre capacity
AMAR Reply
which of the following microorganisms are classified as eukaryotic?
Semugab Reply
how do I see the list?
what are the choices?
dear tell us the choices
mr semugab give us the list please
what are the new discoveries of microorganisms
Ezibon Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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