Guide to Disinfectants & Antiseptics

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Ever wondered what compounds help kitchen cleaners keep your kitchen surfaces bacteria free? Or about the compounds that help antiseptic creams do their job? In this graphic, we take a look at some of the compounds used for antisepsis and disinfection, and where they’re commonly used. There’s also a look at how they all work in the article below!

Alcohols

Where are they found?

Alcohols are commonly found in hospital hand sanitisers. Ethanol and isopropyl alcohol are the two most commonly used compounds, usually in 60-90% solutions (by volume).

How do they work?

In suitable concentrations, alcohols are effective against bacteria, fungi, and some types of virus. It’s suspected that they work by denaturing (malforming) proteins.

Advantages & disadvantages:

Alcohols are effective against a range of microorganisms, particularly bacteria. However, they don’t affect bacterial spores and some viruses, and don’t penetrate organic protein material, so aren’t particularly useful for sterilisation. Additionally, they require a long contact time with the surface in order to be effective, and this is sometimes difficult to achieve as they evaporate easily!

Aldehydes

Where are they found?

Usually used to sterilise medical instruments in hospital settings. Additionally, they can be used for preservation – Damien Hirst’s 1991 artwork, ‘The Physical Impossibility of Death in the Mind of Someone Living’, used formaldehyde to preserve a whole shark, and it’s also used in embalming fluids.

How do they work?

Aldehydes have a broad spectrum of activity against bacteria, fungi, and viruses. They act by alkylating groups in proteins and other important cellular molecules.

Advantages & disadvantages:

The aldehydes used are highly toxic and a long contact time is required to kill microorganisms. However, they do not damage rubber or plastic, making them useful for sterilising devices such as catheters.

Biguanides

Where are they found?

Chlorhexidine digluconate is often used in antiseptic creams in combination with other ingredients, and in many mouthwash products. It can also be combined with alcohols for skin antisepsis during surgery.

How do they work?

Biguanides are active against bacteria, and show a degree of activity against viruses and fungi which can be enhanced by combination with other agents. It’s thought that biguanides stick to cell membranes, causing them to leak small molecules, and making proteins form solid deposits.

Advantages & disadvantages:

Due to their low toxicity, biguanides can be used to treat wounds and in mouthwash. However, they’re not particularly efficient against many viruses. Though they are quite slow-acting, they do have some residual activity, unlike alcohols.

Bisphenols

Where are they found?

The most notable bisphenol is triclosan, commonly found in antibacterial soap products.

How do they work?

The exact mechanism is still unknown, but is thought to involve increasing permeability of cell membranes. They’re most effective against gram-positive bacteria (whose cells have a thick layer of peptidoglycan surrounding them).

Advantages & disadvantages:

Less effective against gram-negative bacteria, fungi, and viruses. Triclosan has been found to have negative cumulative effects on the skin, and can also persist and accumulate in the environment, meaning some concern surrounds its use in soaps.

Diamidines

Where are they found?

Diamidines are mainly used for treatment of wounds.

How do they work?

The manner in which these agents work is unknown. As they have been shown to stop cells taking in oxygen, and also cause amino acids to leak out of cells, it’s thought they likely work in some way by adhering to the surfaces of cells.

Advantages & disadvantages:

Active against gram positive bacteria, but less so against gram negative bacteria. Still work in the presence of organic matter.

Halogen-releasing

Where are they found?

Halogen-releasing compounds are found in household bleach. Iodine can be used to help disinfect the skin and prevent infections.

How do they work?

Halogens are strong oxidising agents, and are effective against all microorganisms. Though the exact mechanisms of action is unknown, they work primarily by destroying proteins in cells.

Advantages & disadvantages:

Iodine solutions can cause staining and irritation when applied to the skin; however, iodine tinctures, which suspend the iodine in a carrier, can help reduce this. They are inactivated by protein-containing materials, so don’t work as well in the presence of organic material.

Metal derivatives

Where are they found?

The mercury-containing compound thiomersal can be used as a preservative in vaccines, though its use has declined somewhat as a result of fabricated links with autism. Silver-containing compounds can be used to prevent infection of burn wounds.

How do they work?

The metals can bind to proteins and enzymes and interfere with cell processes. Metal-containing compounds work against a broad spectrum of microorganisms.

Advantages & disadvantages:

The toxic effects of mercury now restrict its use in most applications. Silver is relatively non-toxic, but accumulates in the body, and can cause the condition argyrosis which turns skin blue.

Peroxygens

Where are they found?

Commonly used for sterilisation, particularly of surgical tools and surfaces, and antisepsis.

How do they work?

Peroxygen compounds have a broad spectrum of activity, effective against bacteria, fungi, and viruses. They work by reacting with proteins and enzymes, and making cell walls more permeable.

Advantages & disadvantages:

The breakdown products of peroxygen compounds are environmentally-friendly: for hydrogen peroxide, water and oxygen are produced, whilst peracetic acid creates oxygen and acetic acid as decomposition products. Their instability does mean that stabilisers sometimes need to be added to solutions, however. Their effectiveness wanes at low concentrations.

Phenolics

Where are they found?

Often used to disinfect surfaces in hospital and laboratory settings, and they are contributors to the characteristic hospital smell.

How do they work?

Phenolic compounds have a broad spectrum of activity, affecting bacteria, fungi, and some viruses. They work by disrupting cell walls and membranes, and reacting with proteins and enzymes.

Advantages & disadvantages:

Phenol is no longer used as a disinfectant due to its toxicity and carcinogenicity. Skin absorption and irritation is still a possibility with the other compounds still currently used. They don’t kill bacteria spores, and the presence of organic material can decrease their effectiveness.

Quaternary ammonium compounds

Where are they found?

Commonly found in kitchen cleaning sprays, but some are also found in antiseptic creams.

How do they work?

They inactivate enzymes and react with proteins, as well as damaging cell membranes. They are most effective against gram positive bacteria, but also have some activity against gram negative bacteria, and some viruses.

Advantages & disadvantages:

Non-toxic, so can be used in areas where food preparation takes place. They do not kill bacterial spores, however. They are also not recommended for antisepsis due to the possibility of gram negative bacteria growing in the solutions.

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References & Further Reading