Mechanism of action of antiseptics

Levels of application of antimicrobial agents

Non-specific antimicrobial agents are usually divided into two large groups depending on their site of action. At the systemic level, antiseptics are intended exclusively for topical use. They are applied directly to damaged or intact tissues of the human body. The effect of using such drugs is realized strictly at the level of the treated surface. This can be the skin, various mucous membranes, an open wound, or an anatomical cavity. The most important characteristic of antiseptics is that they generally do not have a systemic effect on the macroorganism.

In turn, disinfectants have a different scope of application. They are used exclusively for treating inanimate objects in the external environment. The main purpose of using disinfectants is to reliably prevent the transmission of infection from a source to a susceptible organism via transmission factors.

Molecular mechanisms of drug action

Antiseptics and disinfectants exert their microbe-killing effect through various mechanisms. The specific type of impact directly depends on the chemical structure of the substance used. At the molecular level, the following main groups of drugs and their mechanisms of action are distinguished:

• Oxidizing agents. They work by actively releasing atomic oxygen. This process leads to powerful oxidation of vital structural components of the microbial cell, making its further survival impossible.
• Halogens. Halogen-based preparations have a dual effect. First, they cause halogenation of cellular proteins and nucleic acids. Second, they exert a pronounced oxidizing effect on the pathogen's structures.
• Alcohols and aldehydes. These chemical compounds are lethal to bacteria as they cause irreversible protein denaturation. In addition, their mechanism of action includes the alkylation of amino groups, which completely disrupts the normal functioning of the microbial cell.
• Detergents. Surface-active substances attack the envelopes of microorganisms. Their main target is the lipid layer of the cell membrane, the destruction of which leads to bacterial lysis.
• Heavy metal salts. Heavy metal ions bind chemically with sulfhydryl groups of bacterial enzymes and structural proteins. The result of this binding is total protein coagulation.
• Dyes. The specific mechanism of action of dyes lies in their ability to intercalate directly into the microorganism's nucleic acids. This grossly disrupts the replication processes of genetic material.
• Phenols. Phenolic compounds act comprehensively: they provoke the coagulation of intracellular proteins and simultaneously cause a critical disruption of cell membrane permeability.

Pathogen evolution and formation of hospital strains

Despite the high efficacy of antiseptics and disinfectants, microorganisms are capable of evolving. Initially, wild-type populations of many bacteria have low environmental persistence and remain extremely sensitive to standard antiseptic and disinfectant agents. However, hospital settings trigger the mechanism of hospital strain formation.

This process begins with the acquisition of resistance. Microorganisms are forced to constantly adapt to the extremely aggressive factors of the hospital environment. Such factors include regular ultraviolet irradiation, continuous surface desiccation, as well as the continuous impact of chemical disinfectants and pharmacological antibiotics.

As a result of this pressure, strict selection occurs. Surviving resistant strains begin to dominate, gaining an undeniable evolutionary advantage over wild-type populations. The end result of this process is the emergence of hospital strains—specific varieties of microorganisms that are maximally adapted to the harsh conditions of a particular medical facility.

Pathogenicity factors and barrier overcoming

In addition to developing resistance to external influences, microorganisms possess their own pathogenicity factors that allow them to successfully colonize host tissues. Bacterial enzymatic activity plays an important role.

Certain strains are capable of producing a specific enzyme—neuraminidase. The mechanism of action of this enzyme consists in the targeted destruction of glycoproteins. In particular, this is clearly manifested when acting on the vaginal mucosa. The destruction of the glycoprotein layer critically reduces the protective properties of the natural biological barrier, facilitating the process of invasion and subsequent reproduction of microorganisms in tissues, despite the topical application of antiseptics.

Class and exam questions

What else to study on this topic

• Mechanisms of amino group alkylation by aldehydes and alcohols
• The process of halogenation of bacterial nucleic acids
• The role of neuraminidase in the destruction of mucous membrane glycoproteins
• Differences between wild-type populations and adapted hospital strains
• The effect of UV irradiation and desiccation on microorganism survival

Other topics in the "Additional Topics" section

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.