Disinfectants and Sterilization

Disinfectants

• Disinfectants are chemical agents designed to inactivate or destroy microorganisms on inert surfaces.
• Disinfection does not necessarily kill all microorganisms, especially resistant bacterial spores.
• Disinfectants work by destroying the cell wall of microbes or interfering with their metabolism.

Types of Disinfectants

• Sanitizers: substances that simultaneously clean and disinfect.
• Disinfectants: kill more germs than sanitizers and are used to clean surfaces like floors and building premises.

How Disinfectants Work

• Disinfectants kill bacteria by causing protein damage and outer layer rupture, leading to DNA leakage.

Bacterial Resistance

• Bacterial endospores are most resistant to disinfectants, but some fungi, viruses, and bacteria also possess some resistance.

Disinfectant Properties

• A perfect disinfectant would offer complete microbiological sterilization without harming humans and useful forms of life, be inexpensive, and non-corrosive.
• Most disinfectants are also potentially harmful (even toxic) to humans or animals.

Alcohols

• Alcohols are effective when combined with distilled water to facilitate diffusion through the cell membrane.
• A mixture of 70% ethanol or isopropanol diluted in water is effective against a wide spectrum of bacteria.

Aldehydes

• Aldehydes, such as formaldehyde and glutaraldehyde, have a wide microbicidal activity and are sporicidal and fungicidal.
• Some bacteria have developed resistance to glutaraldehyde, which can cause asthma and other health hazards.

Oxidizing Agents

• Oxidizing agents act by oxidizing the cell membrane of microorganisms, leading to cell lysis and death.
• Hydrogen peroxide is used in hospitals to disinfect surfaces, and it is used in solution alone or in combination with other chemicals as a high-level disinfectant.

Hydrogen Peroxide

• Hydrogen peroxide vapor is used as a medical sterilant and room disinfectant.
• Hydrogen peroxide has the advantage that it decomposes to form oxygen and water, leaving no long-term residues.

Other Disinfectants

• Potassium permanganate (KMnO4) is a purplish-black crystalline powder used to disinfect aquariums and community swimming pools.
• Chlorine is used for applications such as deactivating pathogens in drinking water, swimming pool water, and wastewater.

Antiseptics

• Antiseptics are antimicrobial substances applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction.
• Antiseptics are generally distinguished from antibiotics by the latter's ability to safely destroy bacteria within the body, and from disinfectants, which destroy microorganisms found on non-living objects.

Antimicrobial Agents

• Antibacterials: antiseptics that have the proven ability to act against bacteria.
• Viricides or antivirals: microbicides that destroy virus particles.
• Antifungals or antimycotics: pharmaceutical fungicides used to treat and prevent mycosis (fungal infection).

Disinfectants are chemical agents designed to inactivate or destroy microorganisms on inert surfaces. Learn about the difference between disinfection and sterilization and how they work.