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Classification and Mode of Action of Disinfectants

Home Disinfectants, Non-chemical Disinfectants, Oxidizing Disinfectants, Air Disinfectants, Chemical Disinfectants, Alcohol, Aldehyde, Phenols etc.
Disinfectants are chemical agents that are meant to destroy microorganisms such as bacteria, viruses, and fungus. Surfactants (such as dishwashing liquid) are meant to remove chemicals from an area without necessarily harming the items they remove, as opposed to disinfectants (such as soap). Heat and ultraviolet light are examples of radiation that may be considered disinfectants depending on their context.

Decontamination and sterilization are often carried out using disinfectants, but disinfecting something does not imply full sterilization. Disinfectants are designed to kill harmful pathogens, whereas sterilization is designed to ensure that all living and foreign matter is completely removed from the sterilized area.

Disinfectants come in a wide variety of chemical types, but no disinfectant is ideal for every job. Likewise, disinfectants that kill one type of bacteria may not kill another type of bacteria, and disinfectants that kill one type of bacteria may not kill another. In addition to safety and reactivity, disinfectants should also be chosen based on their efficacy. Highly reactive disinfectants may deteriorate or destroy particular surfaces when applied to a surface that has been polluted with specific substances.


Home Disinfectants

Chlorine bleach (typically a >10% solution of sodium hypochlorite) is the most cost-effective home disinfectant and is effective against the majority of common pathogens, including disinfectant-resistant organisms such as tuberculosis (mycobacterium tuberculosis), hepatitis B and C, fungi, and antibiotic-resistant strains of staphylococcus and enterococcus. It has a disinfecting effect on some parasite organisms.

The advantages of chlorine bleach are its low cost and quick action. However, it is irritating to mucous membranes and skin on touch, has a strong odor, and when combined with other cleaning chemicals such as ammonia and vinegar, it can produce unpleasant gases such as chlorine.

Non-chemical Disinfectants

The process of disinfecting flat surfaces such as dental equipment using high-intensity shortwave ultraviolet light, but without disinfecting porous materials that are opaque to light such as wood or foam, is known as UV germicidal irradiation. Municipal water treatment also makes use of ultraviolet light. Microbiology labs use ultraviolet lighting and turn it on only when no one is present (such as at night).

The phrase "sunlight is the finest disinfectant" became widespread in the United States around 1913. Because ultraviolet (UV) photons from sunlight may be used to sterilize, the Earth's ozone layer prevents the most effective wavelengths from being emitted. As a result, UV light-emitting equipment, such as those used to cleanse some hospital rooms, are more effective disinfectants than sunshine.

Disinfection and sterilization can be accomplished by the use of heat treatment.

Oxidizing Disinfectants

  • By oxidizing the cellular membrane of microorganisms, oxidizing agents cause a loss of structure and ultimately impair the ability of the cells to function. Because chlorine and oxygen are potent oxidizers, the following disinfectants work in this manner:
  • Electrolyzed water, often known as "Anolyte," is an oxidizing, acidic hypochlorite solution produced by electrolysis of sodium chloride into sodium hypochlorite; hypochlorous acid being the major oxychlorine species.
  • Hydrogen peroxide, alone or in conjunction with other chemicals, is used to disinfect surfaces in hospitals. Colloidal silver is occasionally combined with hydrogen peroxide. It is frequently favored since it produces considerably less allergic responses than other disinfectants. Foil containers are also disinfected using this chemical in the food packaging industry. As an antiseptic, a 3% solution is also utilized.
  • Hydrogen peroxide vapour is used as a medicinal sterilant and as a room disinfectant. Hydrogen peroxide has the benefit of decomposing to form oxygen and water, leaving no long-term leftovers. OSHA's allowable exposure level is 1 ppm.
  • Accelerated Hydrogen Peroxide, 2% solution (the antibacterial effect of hydrogen peroxide can be boosted by surfactants and organic acids), stable for longer use, provides high-level disinfection in 5 minutes, and is appropriate for sanitizing hard plastic medical equipment such as endoscopes. The research reveals that products based on Accelerated Hydrogen Peroxide, in addition to being effective germicides, are also safer for people and environmentally friendly.
  • Ozone is a gas that may be used to disinfect water, laundry, food, air, and surfaces. It is chemically aggressive and degrades numerous organic molecules, leading in quick decolorization and deodorization as well as disinfection. Regardless, due to its high reactivity, ozone has a wide variety of uses ranging from municipal to industrial water treatment.

Air Disinfectants

  • A disinfectant is a chemical agent that may destroy germs in the air.
  • As an air disinfectant, the aerosol or vapor must be dispensed at a sufficiently high concentration to significantly reduce the number of viable infectious microorganisms in the air.
  • There are various hydrocarbons, such as propylene glycol and triethylene glycol, which are effective air disinfectants since they are lethal to microorganisms and not toxic to mammals if they were inactive. They are also very effective against a variety of bacteria and mold fungi, such as Penicillium chrysogenum.

Chemical Disinfectants


  • Alcohol - Alcohols have relatively rapid bactericidal effects when used in combination with distilled water (60 to 70% volume-to-volume concentration) to facilitate diffusion through the cell membrane and facilitate diffusion through the cell membrane. Methanol vapour has been used as fungicide, while ethanol 60 to 70% by volume and isopropanol 50 to 60% by volume are used as disinfectants. Inactivating lipid-enveloped viruses (such as HIV, hepatitis B, and hepatitis C) requires high-concentration combinations (60 percent ethanol plus 5 percent isopropanol, for example). Sodium alcohols (propyl, butyl, amyl, etc.) are far more germicidal than ethyl alcohol. Some vaccines contain alcohol as a preservative.
  • Aldehyde - Among the many aldehydes used for disinfection, formaldehyde (HCHO) has the widest range of microbiocidal activity as well as being sporicidal and fungicidal. Some instruments can be sterilized with formaldehyde in solution. There is also ortho-phthalaldehyde used sometimes.
  • Phenol and its derivatives - The most major byproduct of coal tar distillation is phenol. Bactericidal activity of phenol 1 percent Many phenol derivatives are more effective and less expensive. Some household disinfectants use phenols as active components. They're also in several mouthwashes, as well as disinfecting soap and handwashes. Cats and newborn humans are both poisoned by phenols. Because it is less corrosive than phenol, o-phenylphenol is frequently employed in its place.
  • Hexachlorophene is a phenol that was originally used as a germicidal addition in several home items until it was outlawed owing to concerns about its safety.
  • Chloroxylenol is a primary ingredient in Dettol, a household disinfectant and antiseptic.
  • Thymol, derived from the plant thyme, is an active component in various "wide spectrum" disinfectants, which frequently make environmental claims. It is utilised in pharmaceutical formulations as a stabiliser. It possesses antiseptic, antibacterial, and antifungal properties and was once employed as a vermifuge.
  • Amylmetacresol is found in Strepsils, a throat disinfectant.
  • Although it is not a phenol, 2,4-dichlorobenzyl alcohol has comparable effects to phenols but cannot inactivate viruses.
  • Quaternary ammonium compounds ("quats"), such as benzalkonium chloride, are commonly used to control microorganisms such as non-enveloped viruses such as norovirus, rotavirus, or polio virus, bacteria, and harmful fungi on floors, walls, nursing homes, and other public areas within (3–5 minutes).
  • They are also utilized in the dairy, egg, and fishing sectors as skin antiseptics and sanitizing agents. In industrial water systems, quats are used as a water additive to control undesirable biological growth by killing algae and biocides.
  • Terpenes: Pine oil and Thyme are examples of terpenes. Pine oil is a disinfectant that is slightly antiseptic and effective against fungus, bacteria, influenza virus, and other pathogens. It will destroy the agents that cause typhoid, gastroenteritis (certain agents), rabies, cholera, some types of meningitis, whooping cough, gonorrhoea, and various types of dysentery.
  • It is ineffective against spore-borne infections like tetanus or anthrax, as well as non-enveloped viruses like poliovirus, rhinovirus, hepatitis B, or hepatitis C.
  • Thymol may also be used as a medical disinfectant and general-purpose disinfectant; it is used to treat ringworm infections in alcohol solutions and dusting powders.
  • An FDA-approved disinfectant, lactic acid can be used to disinfect surfaces. Because of its natural and environmental features, it has gained commercial importance.


Acids and Bases
Sulphur dioxide, sulfurous acid, potassium hydroxide, calcium hydroxide, sodium hydroxide, magnesium hydroxide.

Chlorine - This category includes chlorine, hypochlorite, and hypochlorous acid aqueous solutions. Chlorine-releasing chemicals and their salts are occasionally included in this category. A concentration of 1 ppm of accessible chlorine is frequently adequate to destroy bacteria and viruses, although spores and mycobacteria need greater amounts. Chlorine has been utilized in a variety of applications, including pathogen deactivation in drinking water, swimming pool water, and wastewater, disinfection of domestic environments, and textile bleaching.

Iodine - Iodophors are made by combining iodine with a solubilizing agent. Brewers and winemakers frequently use diluted iodophor to sterilize equipment and bottles; its main benefit over other sanitizers is that it does not require washing when used in suitable amounts.

Other Disinfectants

Biguanide polymer - At relatively low concentrations (10 mg/l), polyaminopropyl biguanide is particularly bactericidal. It works in an unusual way: the polymer strands are absorbed into the bacterial cell wall, disrupting the membrane and reducing its permeability, which is fatal to bacteria. It has also been shown to attach to bacterial DNA, change transcription, and induce deadly DNA damage. It is very poisonous to higher species with more sophisticated and protective membranes, such as human cells.

Detergents and soaps - They are frequently used as surface active agents, wetting agents, and emulsifiers. They are divided into four categories: anionic, cationic, non-ionic, and amphoteric. Cationic surface-active compounds are the most significant antibacterial agents. For example, cetrimide, benzalkonium chloride, and so on. Anionic substances include soap and sodium lauryl sulphate. Soaps made from saturated fatty acids are more efficient against gramme negative bacilli, whilst those made from unsaturated acids are more effective against gramme positive bacilli. Ionization does not occur in nonionic detergents. These compounds, however, do not have significant anti-microbial action. The detergent characteristics of anionic surfactants are coupled with the disinfecting properties of cationic surfactants in amphoteric substances. Tego compounds, for example. Ionization does not occur in nonionic detergents. These compounds, however, do not have significant anti-microbial action. The detergent characteristics of anionic surfactants are coupled with the disinfecting properties of cationic surfactants in amphoteric substances. Tego compounds, for example.

Sodium bicarbonate - (NaHCO3) contains antifungal, antiviral, and antibacterial activities, however they are too weak to be useful in a household context.

Dyes - To limit bacterial growth, a variety of colours have been utilised. Bactericides are more effective with basic colours than with acidic dyes. Antimicrobial compounds such as acridine and triphenylmethane dyes are routinely employed.

Mode of Action of Disinfectants

Many disinfectants are utilised in the pharmaceutical industry for cleanliness and disinfection. Based on their method of action, they have varying antibacterial characteristics. Disinfectants with distinct modes of action can assist to avoid the development of resistance in microorganisms.

Modes of Actions Includes -

Aldehydes - In addition to having antibacterial, antifungal, and antiviral properties, it also has sporicidal properties. The spores of Bacillus subtilis and Clostridium sporogenes can be destroyed by these enzymes. Aldehydes such as glutaraldehyde and formaldehyde are often employed as disinfectants. The enzyme activity in the cell was denatured by a 2 percent solution in habits.

Alcohols - Alcohols of all sorts are antiseptic and antibacterial agents. When combined with water, they are quite effective. These are effective against the polio and rhinoviruses. In the pharmaceutical industry, 70% ethyl alcohol and isopropyl alcohol solutions are routinely utilized as hand disinfectants. The cell wall proteins are denatured by alcohol.

Chlorine and sodium hypochlorite - For disinfection, chlorine or sodium hypochlorite are most commonly used. This is an agent that works against bacteria that generate spores. Cells' enzymes interact with it when it acts as an oxidizing agent.

Phenols - They are disinfectants known as chlorocresol and chloroxylenol. Besides having antiviral and antifungal properties, they are general disinfectants. They denature cellular enzymes and proteins.

Hydrogen peroxide - Besides that, it also acts as an oxidizing agent on DNA and proteins of cells. Bacteria and fungus are effectively killed by a 5% solution in water. It is effective in the sanitation of water systems. Bacterial spores and viruses are resistant to high concentrations. It functions as an oxidant and draws important cell components such as DNA, lipids, and proteins.

Benzalkonium chloride - A solution of 0.0002 percent is effective against the vegetative cell. It promotes coagulation of cell contents by increasing the permeability of the cell membrane.

Chlorhexidine gluconate - A 0.0002 percent solution is effective against the vegetative cell. It stimulates cellular coagulation by increasing the permeability of the cell membrane.

Disinfectants used in the sanitation and cleaning sectors, as well as the pharmaceutical industry, must be chosen based on their mode of action. Disinfectants with the same mechanism may lead to the development of habitation and microorganisms. As a result, the disinfectants' modes of action should differ.
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Ankur Choudhary is India's first professional pharmaceutical blogger, author and founder of Pharmaceutical Guidelines, a widely-read pharmaceutical blog since 2008. Sign-up for the free email updates for your daily dose of pharmaceutical tips.
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